Commit | Line | Data |
---|---|---|
1da177e4 | 1 | |
00354cfb JV |
2 | Linux Ethernet Bonding Driver HOWTO |
3 | ||
a549952a | 4 | Latest update: 23 September 2009 |
1da177e4 LT |
5 | |
6 | Initial release : Thomas Davis <tadavis at lbl.gov> | |
7 | Corrections, HA extensions : 2000/10/03-15 : | |
8 | - Willy Tarreau <willy at meta-x.org> | |
9 | - Constantine Gavrilov <const-g at xpert.com> | |
10 | - Chad N. Tindel <ctindel at ieee dot org> | |
11 | - Janice Girouard <girouard at us dot ibm dot com> | |
12 | - Jay Vosburgh <fubar at us dot ibm dot com> | |
13 | ||
14 | Reorganized and updated Feb 2005 by Jay Vosburgh | |
6224e01d AK |
15 | Added Sysfs information: 2006/04/24 |
16 | - Mitch Williams <mitch.a.williams at intel.com> | |
1da177e4 | 17 | |
00354cfb JV |
18 | Introduction |
19 | ============ | |
20 | ||
21 | The Linux bonding driver provides a method for aggregating | |
22 | multiple network interfaces into a single logical "bonded" interface. | |
23 | The behavior of the bonded interfaces depends upon the mode; generally | |
24 | speaking, modes provide either hot standby or load balancing services. | |
25 | Additionally, link integrity monitoring may be performed. | |
1da177e4 | 26 | |
00354cfb JV |
27 | The bonding driver originally came from Donald Becker's |
28 | beowulf patches for kernel 2.0. It has changed quite a bit since, and | |
29 | the original tools from extreme-linux and beowulf sites will not work | |
30 | with this version of the driver. | |
1da177e4 | 31 | |
00354cfb JV |
32 | For new versions of the driver, updated userspace tools, and |
33 | who to ask for help, please follow the links at the end of this file. | |
1da177e4 LT |
34 | |
35 | Table of Contents | |
36 | ================= | |
37 | ||
38 | 1. Bonding Driver Installation | |
39 | ||
40 | 2. Bonding Driver Options | |
41 | ||
42 | 3. Configuring Bonding Devices | |
6224e01d AK |
43 | 3.1 Configuration with Sysconfig Support |
44 | 3.1.1 Using DHCP with Sysconfig | |
45 | 3.1.2 Configuring Multiple Bonds with Sysconfig | |
46 | 3.2 Configuration with Initscripts Support | |
47 | 3.2.1 Using DHCP with Initscripts | |
48 | 3.2.2 Configuring Multiple Bonds with Initscripts | |
49 | 3.3 Configuring Bonding Manually with Ifenslave | |
00354cfb | 50 | 3.3.1 Configuring Multiple Bonds Manually |
6224e01d | 51 | 3.4 Configuring Bonding Manually via Sysfs |
1da177e4 | 52 | |
6224e01d AK |
53 | 4. Querying Bonding Configuration |
54 | 4.1 Bonding Configuration | |
55 | 4.2 Network Configuration | |
1da177e4 | 56 | |
6224e01d | 57 | 5. Switch Configuration |
1da177e4 | 58 | |
6224e01d | 59 | 6. 802.1q VLAN Support |
1da177e4 | 60 | |
6224e01d AK |
61 | 7. Link Monitoring |
62 | 7.1 ARP Monitor Operation | |
63 | 7.2 Configuring Multiple ARP Targets | |
64 | 7.3 MII Monitor Operation | |
1da177e4 | 65 | |
6224e01d AK |
66 | 8. Potential Trouble Sources |
67 | 8.1 Adventures in Routing | |
68 | 8.2 Ethernet Device Renaming | |
69 | 8.3 Painfully Slow Or No Failed Link Detection By Miimon | |
1da177e4 | 70 | |
6224e01d | 71 | 9. SNMP agents |
1da177e4 | 72 | |
6224e01d | 73 | 10. Promiscuous mode |
1da177e4 | 74 | |
6224e01d AK |
75 | 11. Configuring Bonding for High Availability |
76 | 11.1 High Availability in a Single Switch Topology | |
77 | 11.2 High Availability in a Multiple Switch Topology | |
78 | 11.2.1 HA Bonding Mode Selection for Multiple Switch Topology | |
79 | 11.2.2 HA Link Monitoring for Multiple Switch Topology | |
00354cfb | 80 | |
6224e01d AK |
81 | 12. Configuring Bonding for Maximum Throughput |
82 | 12.1 Maximum Throughput in a Single Switch Topology | |
83 | 12.1.1 MT Bonding Mode Selection for Single Switch Topology | |
84 | 12.1.2 MT Link Monitoring for Single Switch Topology | |
85 | 12.2 Maximum Throughput in a Multiple Switch Topology | |
86 | 12.2.1 MT Bonding Mode Selection for Multiple Switch Topology | |
87 | 12.2.2 MT Link Monitoring for Multiple Switch Topology | |
1da177e4 | 88 | |
6224e01d AK |
89 | 13. Switch Behavior Issues |
90 | 13.1 Link Establishment and Failover Delays | |
91 | 13.2 Duplicated Incoming Packets | |
1da177e4 | 92 | |
6224e01d AK |
93 | 14. Hardware Specific Considerations |
94 | 14.1 IBM BladeCenter | |
1da177e4 | 95 | |
6224e01d | 96 | 15. Frequently Asked Questions |
00354cfb | 97 | |
6224e01d | 98 | 16. Resources and Links |
1da177e4 LT |
99 | |
100 | ||
101 | 1. Bonding Driver Installation | |
102 | ============================== | |
103 | ||
104 | Most popular distro kernels ship with the bonding driver | |
105 | already available as a module and the ifenslave user level control | |
106 | program installed and ready for use. If your distro does not, or you | |
107 | have need to compile bonding from source (e.g., configuring and | |
108 | installing a mainline kernel from kernel.org), you'll need to perform | |
109 | the following steps: | |
110 | ||
111 | 1.1 Configure and build the kernel with bonding | |
112 | ----------------------------------------------- | |
113 | ||
00354cfb | 114 | The current version of the bonding driver is available in the |
1da177e4 | 115 | drivers/net/bonding subdirectory of the most recent kernel source |
00354cfb JV |
116 | (which is available on http://kernel.org). Most users "rolling their |
117 | own" will want to use the most recent kernel from kernel.org. | |
1da177e4 LT |
118 | |
119 | Configure kernel with "make menuconfig" (or "make xconfig" or | |
120 | "make config"), then select "Bonding driver support" in the "Network | |
121 | device support" section. It is recommended that you configure the | |
122 | driver as module since it is currently the only way to pass parameters | |
123 | to the driver or configure more than one bonding device. | |
124 | ||
00354cfb JV |
125 | Build and install the new kernel and modules, then continue |
126 | below to install ifenslave. | |
1da177e4 LT |
127 | |
128 | 1.2 Install ifenslave Control Utility | |
129 | ------------------------------------- | |
130 | ||
131 | The ifenslave user level control program is included in the | |
132 | kernel source tree, in the file Documentation/networking/ifenslave.c. | |
133 | It is generally recommended that you use the ifenslave that | |
134 | corresponds to the kernel that you are using (either from the same | |
135 | source tree or supplied with the distro), however, ifenslave | |
136 | executables from older kernels should function (but features newer | |
137 | than the ifenslave release are not supported). Running an ifenslave | |
138 | that is newer than the kernel is not supported, and may or may not | |
139 | work. | |
140 | ||
141 | To install ifenslave, do the following: | |
142 | ||
143 | # gcc -Wall -O -I/usr/src/linux/include ifenslave.c -o ifenslave | |
144 | # cp ifenslave /sbin/ifenslave | |
145 | ||
146 | If your kernel source is not in "/usr/src/linux," then replace | |
147 | "/usr/src/linux/include" in the above with the location of your kernel | |
148 | source include directory. | |
149 | ||
150 | You may wish to back up any existing /sbin/ifenslave, or, for | |
151 | testing or informal use, tag the ifenslave to the kernel version | |
152 | (e.g., name the ifenslave executable /sbin/ifenslave-2.6.10). | |
153 | ||
154 | IMPORTANT NOTE: | |
155 | ||
156 | If you omit the "-I" or specify an incorrect directory, you | |
157 | may end up with an ifenslave that is incompatible with the kernel | |
158 | you're trying to build it for. Some distros (e.g., Red Hat from 7.1 | |
159 | onwards) do not have /usr/include/linux symbolically linked to the | |
160 | default kernel source include directory. | |
161 | ||
6224e01d AK |
162 | SECOND IMPORTANT NOTE: |
163 | If you plan to configure bonding using sysfs, you do not need | |
164 | to use ifenslave. | |
1da177e4 LT |
165 | |
166 | 2. Bonding Driver Options | |
167 | ========================= | |
168 | ||
9a6c6867 JV |
169 | Options for the bonding driver are supplied as parameters to the |
170 | bonding module at load time, or are specified via sysfs. | |
171 | ||
172 | Module options may be given as command line arguments to the | |
173 | insmod or modprobe command, but are usually specified in either the | |
174 | /etc/modules.conf or /etc/modprobe.conf configuration file, or in a | |
175 | distro-specific configuration file (some of which are detailed in the next | |
176 | section). | |
177 | ||
178 | Details on bonding support for sysfs is provided in the | |
179 | "Configuring Bonding Manually via Sysfs" section, below. | |
1da177e4 LT |
180 | |
181 | The available bonding driver parameters are listed below. If a | |
182 | parameter is not specified the default value is used. When initially | |
183 | configuring a bond, it is recommended "tail -f /var/log/messages" be | |
184 | run in a separate window to watch for bonding driver error messages. | |
185 | ||
186 | It is critical that either the miimon or arp_interval and | |
187 | arp_ip_target parameters be specified, otherwise serious network | |
188 | degradation will occur during link failures. Very few devices do not | |
189 | support at least miimon, so there is really no reason not to use it. | |
190 | ||
191 | Options with textual values will accept either the text name | |
00354cfb JV |
192 | or, for backwards compatibility, the option value. E.g., |
193 | "mode=802.3ad" and "mode=4" set the same mode. | |
1da177e4 LT |
194 | |
195 | The parameters are as follows: | |
196 | ||
fd989c83 JV |
197 | ad_select |
198 | ||
199 | Specifies the 802.3ad aggregation selection logic to use. The | |
200 | possible values and their effects are: | |
201 | ||
202 | stable or 0 | |
203 | ||
204 | The active aggregator is chosen by largest aggregate | |
205 | bandwidth. | |
206 | ||
207 | Reselection of the active aggregator occurs only when all | |
208 | slaves of the active aggregator are down or the active | |
209 | aggregator has no slaves. | |
210 | ||
211 | This is the default value. | |
212 | ||
213 | bandwidth or 1 | |
214 | ||
215 | The active aggregator is chosen by largest aggregate | |
216 | bandwidth. Reselection occurs if: | |
217 | ||
218 | - A slave is added to or removed from the bond | |
219 | ||
220 | - Any slave's link state changes | |
221 | ||
222 | - Any slave's 802.3ad association state changes | |
223 | ||
19f59460 | 224 | - The bond's administrative state changes to up |
fd989c83 JV |
225 | |
226 | count or 2 | |
227 | ||
228 | The active aggregator is chosen by the largest number of | |
229 | ports (slaves). Reselection occurs as described under the | |
230 | "bandwidth" setting, above. | |
231 | ||
232 | The bandwidth and count selection policies permit failover of | |
233 | 802.3ad aggregations when partial failure of the active aggregator | |
234 | occurs. This keeps the aggregator with the highest availability | |
235 | (either in bandwidth or in number of ports) active at all times. | |
236 | ||
237 | This option was added in bonding version 3.4.0. | |
238 | ||
1da177e4 LT |
239 | arp_interval |
240 | ||
00354cfb | 241 | Specifies the ARP link monitoring frequency in milliseconds. |
f5b2b966 JV |
242 | |
243 | The ARP monitor works by periodically checking the slave | |
244 | devices to determine whether they have sent or received | |
245 | traffic recently (the precise criteria depends upon the | |
246 | bonding mode, and the state of the slave). Regular traffic is | |
247 | generated via ARP probes issued for the addresses specified by | |
248 | the arp_ip_target option. | |
249 | ||
250 | This behavior can be modified by the arp_validate option, | |
251 | below. | |
252 | ||
00354cfb JV |
253 | If ARP monitoring is used in an etherchannel compatible mode |
254 | (modes 0 and 2), the switch should be configured in a mode | |
255 | that evenly distributes packets across all links. If the | |
256 | switch is configured to distribute the packets in an XOR | |
1da177e4 LT |
257 | fashion, all replies from the ARP targets will be received on |
258 | the same link which could cause the other team members to | |
00354cfb JV |
259 | fail. ARP monitoring should not be used in conjunction with |
260 | miimon. A value of 0 disables ARP monitoring. The default | |
1da177e4 LT |
261 | value is 0. |
262 | ||
263 | arp_ip_target | |
264 | ||
00354cfb JV |
265 | Specifies the IP addresses to use as ARP monitoring peers when |
266 | arp_interval is > 0. These are the targets of the ARP request | |
267 | sent to determine the health of the link to the targets. | |
268 | Specify these values in ddd.ddd.ddd.ddd format. Multiple IP | |
269 | addresses must be separated by a comma. At least one IP | |
270 | address must be given for ARP monitoring to function. The | |
271 | maximum number of targets that can be specified is 16. The | |
272 | default value is no IP addresses. | |
1da177e4 | 273 | |
f5b2b966 JV |
274 | arp_validate |
275 | ||
276 | Specifies whether or not ARP probes and replies should be | |
277 | validated in the active-backup mode. This causes the ARP | |
278 | monitor to examine the incoming ARP requests and replies, and | |
279 | only consider a slave to be up if it is receiving the | |
280 | appropriate ARP traffic. | |
281 | ||
282 | Possible values are: | |
283 | ||
284 | none or 0 | |
285 | ||
286 | No validation is performed. This is the default. | |
287 | ||
288 | active or 1 | |
289 | ||
290 | Validation is performed only for the active slave. | |
291 | ||
292 | backup or 2 | |
293 | ||
294 | Validation is performed only for backup slaves. | |
295 | ||
296 | all or 3 | |
297 | ||
298 | Validation is performed for all slaves. | |
299 | ||
300 | For the active slave, the validation checks ARP replies to | |
301 | confirm that they were generated by an arp_ip_target. Since | |
302 | backup slaves do not typically receive these replies, the | |
303 | validation performed for backup slaves is on the ARP request | |
304 | sent out via the active slave. It is possible that some | |
305 | switch or network configurations may result in situations | |
306 | wherein the backup slaves do not receive the ARP requests; in | |
307 | such a situation, validation of backup slaves must be | |
308 | disabled. | |
309 | ||
310 | This option is useful in network configurations in which | |
311 | multiple bonding hosts are concurrently issuing ARPs to one or | |
312 | more targets beyond a common switch. Should the link between | |
313 | the switch and target fail (but not the switch itself), the | |
314 | probe traffic generated by the multiple bonding instances will | |
315 | fool the standard ARP monitor into considering the links as | |
316 | still up. Use of the arp_validate option can resolve this, as | |
317 | the ARP monitor will only consider ARP requests and replies | |
318 | associated with its own instance of bonding. | |
319 | ||
320 | This option was added in bonding version 3.1.0. | |
321 | ||
1da177e4 LT |
322 | downdelay |
323 | ||
324 | Specifies the time, in milliseconds, to wait before disabling | |
325 | a slave after a link failure has been detected. This option | |
326 | is only valid for the miimon link monitor. The downdelay | |
327 | value should be a multiple of the miimon value; if not, it | |
328 | will be rounded down to the nearest multiple. The default | |
329 | value is 0. | |
330 | ||
dd957c57 JV |
331 | fail_over_mac |
332 | ||
333 | Specifies whether active-backup mode should set all slaves to | |
3915c1e8 JV |
334 | the same MAC address at enslavement (the traditional |
335 | behavior), or, when enabled, perform special handling of the | |
336 | bond's MAC address in accordance with the selected policy. | |
337 | ||
338 | Possible values are: | |
339 | ||
340 | none or 0 | |
341 | ||
342 | This setting disables fail_over_mac, and causes | |
343 | bonding to set all slaves of an active-backup bond to | |
344 | the same MAC address at enslavement time. This is the | |
345 | default. | |
346 | ||
347 | active or 1 | |
348 | ||
349 | The "active" fail_over_mac policy indicates that the | |
350 | MAC address of the bond should always be the MAC | |
351 | address of the currently active slave. The MAC | |
352 | address of the slaves is not changed; instead, the MAC | |
353 | address of the bond changes during a failover. | |
354 | ||
355 | This policy is useful for devices that cannot ever | |
356 | alter their MAC address, or for devices that refuse | |
357 | incoming broadcasts with their own source MAC (which | |
358 | interferes with the ARP monitor). | |
359 | ||
360 | The down side of this policy is that every device on | |
361 | the network must be updated via gratuitous ARP, | |
362 | vs. just updating a switch or set of switches (which | |
363 | often takes place for any traffic, not just ARP | |
364 | traffic, if the switch snoops incoming traffic to | |
365 | update its tables) for the traditional method. If the | |
366 | gratuitous ARP is lost, communication may be | |
367 | disrupted. | |
368 | ||
369 | When this policy is used in conjuction with the mii | |
370 | monitor, devices which assert link up prior to being | |
371 | able to actually transmit and receive are particularly | |
19f59460 | 372 | susceptible to loss of the gratuitous ARP, and an |
3915c1e8 JV |
373 | appropriate updelay setting may be required. |
374 | ||
375 | follow or 2 | |
376 | ||
377 | The "follow" fail_over_mac policy causes the MAC | |
378 | address of the bond to be selected normally (normally | |
379 | the MAC address of the first slave added to the bond). | |
380 | However, the second and subsequent slaves are not set | |
381 | to this MAC address while they are in a backup role; a | |
382 | slave is programmed with the bond's MAC address at | |
383 | failover time (and the formerly active slave receives | |
384 | the newly active slave's MAC address). | |
385 | ||
386 | This policy is useful for multiport devices that | |
387 | either become confused or incur a performance penalty | |
388 | when multiple ports are programmed with the same MAC | |
389 | address. | |
390 | ||
391 | ||
392 | The default policy is none, unless the first slave cannot | |
393 | change its MAC address, in which case the active policy is | |
394 | selected by default. | |
395 | ||
396 | This option may be modified via sysfs only when no slaves are | |
397 | present in the bond. | |
398 | ||
399 | This option was added in bonding version 3.2.0. The "follow" | |
400 | policy was added in bonding version 3.3.0. | |
dd957c57 | 401 | |
1da177e4 LT |
402 | lacp_rate |
403 | ||
404 | Option specifying the rate in which we'll ask our link partner | |
405 | to transmit LACPDU packets in 802.3ad mode. Possible values | |
406 | are: | |
407 | ||
408 | slow or 0 | |
00354cfb | 409 | Request partner to transmit LACPDUs every 30 seconds |
1da177e4 LT |
410 | |
411 | fast or 1 | |
412 | Request partner to transmit LACPDUs every 1 second | |
413 | ||
00354cfb JV |
414 | The default is slow. |
415 | ||
1da177e4 LT |
416 | max_bonds |
417 | ||
418 | Specifies the number of bonding devices to create for this | |
419 | instance of the bonding driver. E.g., if max_bonds is 3, and | |
420 | the bonding driver is not already loaded, then bond0, bond1 | |
b8a9787e JV |
421 | and bond2 will be created. The default value is 1. Specifying |
422 | a value of 0 will load bonding, but will not create any devices. | |
1da177e4 LT |
423 | |
424 | miimon | |
425 | ||
00354cfb JV |
426 | Specifies the MII link monitoring frequency in milliseconds. |
427 | This determines how often the link state of each slave is | |
428 | inspected for link failures. A value of zero disables MII | |
429 | link monitoring. A value of 100 is a good starting point. | |
430 | The use_carrier option, below, affects how the link state is | |
1da177e4 LT |
431 | determined. See the High Availability section for additional |
432 | information. The default value is 0. | |
433 | ||
434 | mode | |
435 | ||
436 | Specifies one of the bonding policies. The default is | |
437 | balance-rr (round robin). Possible values are: | |
438 | ||
439 | balance-rr or 0 | |
440 | ||
441 | Round-robin policy: Transmit packets in sequential | |
442 | order from the first available slave through the | |
443 | last. This mode provides load balancing and fault | |
444 | tolerance. | |
445 | ||
446 | active-backup or 1 | |
447 | ||
448 | Active-backup policy: Only one slave in the bond is | |
449 | active. A different slave becomes active if, and only | |
450 | if, the active slave fails. The bond's MAC address is | |
451 | externally visible on only one port (network adapter) | |
00354cfb JV |
452 | to avoid confusing the switch. |
453 | ||
454 | In bonding version 2.6.2 or later, when a failover | |
455 | occurs in active-backup mode, bonding will issue one | |
456 | or more gratuitous ARPs on the newly active slave. | |
6224e01d | 457 | One gratuitous ARP is issued for the bonding master |
00354cfb JV |
458 | interface and each VLAN interfaces configured above |
459 | it, provided that the interface has at least one IP | |
460 | address configured. Gratuitous ARPs issued for VLAN | |
461 | interfaces are tagged with the appropriate VLAN id. | |
462 | ||
463 | This mode provides fault tolerance. The primary | |
464 | option, documented below, affects the behavior of this | |
465 | mode. | |
1da177e4 LT |
466 | |
467 | balance-xor or 2 | |
468 | ||
00354cfb JV |
469 | XOR policy: Transmit based on the selected transmit |
470 | hash policy. The default policy is a simple [(source | |
471 | MAC address XOR'd with destination MAC address) modulo | |
472 | slave count]. Alternate transmit policies may be | |
473 | selected via the xmit_hash_policy option, described | |
474 | below. | |
475 | ||
476 | This mode provides load balancing and fault tolerance. | |
1da177e4 LT |
477 | |
478 | broadcast or 3 | |
479 | ||
480 | Broadcast policy: transmits everything on all slave | |
481 | interfaces. This mode provides fault tolerance. | |
482 | ||
483 | 802.3ad or 4 | |
484 | ||
485 | IEEE 802.3ad Dynamic link aggregation. Creates | |
486 | aggregation groups that share the same speed and | |
487 | duplex settings. Utilizes all slaves in the active | |
488 | aggregator according to the 802.3ad specification. | |
489 | ||
00354cfb JV |
490 | Slave selection for outgoing traffic is done according |
491 | to the transmit hash policy, which may be changed from | |
492 | the default simple XOR policy via the xmit_hash_policy | |
493 | option, documented below. Note that not all transmit | |
494 | policies may be 802.3ad compliant, particularly in | |
495 | regards to the packet mis-ordering requirements of | |
496 | section 43.2.4 of the 802.3ad standard. Differing | |
497 | peer implementations will have varying tolerances for | |
498 | noncompliance. | |
499 | ||
500 | Prerequisites: | |
1da177e4 LT |
501 | |
502 | 1. Ethtool support in the base drivers for retrieving | |
503 | the speed and duplex of each slave. | |
504 | ||
505 | 2. A switch that supports IEEE 802.3ad Dynamic link | |
506 | aggregation. | |
507 | ||
508 | Most switches will require some type of configuration | |
509 | to enable 802.3ad mode. | |
510 | ||
511 | balance-tlb or 5 | |
512 | ||
513 | Adaptive transmit load balancing: channel bonding that | |
514 | does not require any special switch support. The | |
515 | outgoing traffic is distributed according to the | |
516 | current load (computed relative to the speed) on each | |
517 | slave. Incoming traffic is received by the current | |
518 | slave. If the receiving slave fails, another slave | |
519 | takes over the MAC address of the failed receiving | |
520 | slave. | |
521 | ||
522 | Prerequisite: | |
523 | ||
524 | Ethtool support in the base drivers for retrieving the | |
525 | speed of each slave. | |
526 | ||
527 | balance-alb or 6 | |
528 | ||
529 | Adaptive load balancing: includes balance-tlb plus | |
530 | receive load balancing (rlb) for IPV4 traffic, and | |
531 | does not require any special switch support. The | |
532 | receive load balancing is achieved by ARP negotiation. | |
533 | The bonding driver intercepts the ARP Replies sent by | |
534 | the local system on their way out and overwrites the | |
535 | source hardware address with the unique hardware | |
536 | address of one of the slaves in the bond such that | |
537 | different peers use different hardware addresses for | |
538 | the server. | |
539 | ||
540 | Receive traffic from connections created by the server | |
541 | is also balanced. When the local system sends an ARP | |
542 | Request the bonding driver copies and saves the peer's | |
543 | IP information from the ARP packet. When the ARP | |
544 | Reply arrives from the peer, its hardware address is | |
545 | retrieved and the bonding driver initiates an ARP | |
546 | reply to this peer assigning it to one of the slaves | |
547 | in the bond. A problematic outcome of using ARP | |
548 | negotiation for balancing is that each time that an | |
549 | ARP request is broadcast it uses the hardware address | |
550 | of the bond. Hence, peers learn the hardware address | |
551 | of the bond and the balancing of receive traffic | |
552 | collapses to the current slave. This is handled by | |
553 | sending updates (ARP Replies) to all the peers with | |
554 | their individually assigned hardware address such that | |
555 | the traffic is redistributed. Receive traffic is also | |
556 | redistributed when a new slave is added to the bond | |
557 | and when an inactive slave is re-activated. The | |
558 | receive load is distributed sequentially (round robin) | |
559 | among the group of highest speed slaves in the bond. | |
560 | ||
561 | When a link is reconnected or a new slave joins the | |
562 | bond the receive traffic is redistributed among all | |
00354cfb | 563 | active slaves in the bond by initiating ARP Replies |
6224e01d | 564 | with the selected MAC address to each of the |
1da177e4 LT |
565 | clients. The updelay parameter (detailed below) must |
566 | be set to a value equal or greater than the switch's | |
567 | forwarding delay so that the ARP Replies sent to the | |
568 | peers will not be blocked by the switch. | |
569 | ||
570 | Prerequisites: | |
571 | ||
572 | 1. Ethtool support in the base drivers for retrieving | |
573 | the speed of each slave. | |
574 | ||
575 | 2. Base driver support for setting the hardware | |
576 | address of a device while it is open. This is | |
577 | required so that there will always be one slave in the | |
578 | team using the bond hardware address (the | |
579 | curr_active_slave) while having a unique hardware | |
580 | address for each slave in the bond. If the | |
581 | curr_active_slave fails its hardware address is | |
582 | swapped with the new curr_active_slave that was | |
583 | chosen. | |
584 | ||
b59f9f74 JV |
585 | num_grat_arp |
586 | ||
587 | Specifies the number of gratuitous ARPs to be issued after a | |
588 | failover event. One gratuitous ARP is issued immediately after | |
589 | the failover, subsequent ARPs are sent at a rate of one per link | |
590 | monitor interval (arp_interval or miimon, whichever is active). | |
591 | ||
592 | The valid range is 0 - 255; the default value is 1. This option | |
593 | affects only the active-backup mode. This option was added for | |
594 | bonding version 3.3.0. | |
595 | ||
305d552a BH |
596 | num_unsol_na |
597 | ||
598 | Specifies the number of unsolicited IPv6 Neighbor Advertisements | |
599 | to be issued after a failover event. One unsolicited NA is issued | |
600 | immediately after the failover. | |
601 | ||
602 | The valid range is 0 - 255; the default value is 1. This option | |
603 | affects only the active-backup mode. This option was added for | |
604 | bonding version 3.4.0. | |
605 | ||
1da177e4 LT |
606 | primary |
607 | ||
608 | A string (eth0, eth2, etc) specifying which slave is the | |
609 | primary device. The specified device will always be the | |
610 | active slave while it is available. Only when the primary is | |
611 | off-line will alternate devices be used. This is useful when | |
612 | one slave is preferred over another, e.g., when one slave has | |
613 | higher throughput than another. | |
614 | ||
615 | The primary option is only valid for active-backup mode. | |
616 | ||
a549952a JP |
617 | primary_reselect |
618 | ||
619 | Specifies the reselection policy for the primary slave. This | |
620 | affects how the primary slave is chosen to become the active slave | |
621 | when failure of the active slave or recovery of the primary slave | |
622 | occurs. This option is designed to prevent flip-flopping between | |
623 | the primary slave and other slaves. Possible values are: | |
624 | ||
625 | always or 0 (default) | |
626 | ||
627 | The primary slave becomes the active slave whenever it | |
628 | comes back up. | |
629 | ||
630 | better or 1 | |
631 | ||
632 | The primary slave becomes the active slave when it comes | |
633 | back up, if the speed and duplex of the primary slave is | |
634 | better than the speed and duplex of the current active | |
635 | slave. | |
636 | ||
637 | failure or 2 | |
638 | ||
639 | The primary slave becomes the active slave only if the | |
640 | current active slave fails and the primary slave is up. | |
641 | ||
642 | The primary_reselect setting is ignored in two cases: | |
643 | ||
644 | If no slaves are active, the first slave to recover is | |
645 | made the active slave. | |
646 | ||
647 | When initially enslaved, the primary slave is always made | |
648 | the active slave. | |
649 | ||
650 | Changing the primary_reselect policy via sysfs will cause an | |
651 | immediate selection of the best active slave according to the new | |
652 | policy. This may or may not result in a change of the active | |
653 | slave, depending upon the circumstances. | |
654 | ||
655 | This option was added for bonding version 3.6.0. | |
656 | ||
1da177e4 LT |
657 | updelay |
658 | ||
659 | Specifies the time, in milliseconds, to wait before enabling a | |
660 | slave after a link recovery has been detected. This option is | |
661 | only valid for the miimon link monitor. The updelay value | |
662 | should be a multiple of the miimon value; if not, it will be | |
663 | rounded down to the nearest multiple. The default value is 0. | |
664 | ||
665 | use_carrier | |
666 | ||
667 | Specifies whether or not miimon should use MII or ETHTOOL | |
668 | ioctls vs. netif_carrier_ok() to determine the link | |
669 | status. The MII or ETHTOOL ioctls are less efficient and | |
670 | utilize a deprecated calling sequence within the kernel. The | |
671 | netif_carrier_ok() relies on the device driver to maintain its | |
672 | state with netif_carrier_on/off; at this writing, most, but | |
673 | not all, device drivers support this facility. | |
674 | ||
675 | If bonding insists that the link is up when it should not be, | |
676 | it may be that your network device driver does not support | |
677 | netif_carrier_on/off. The default state for netif_carrier is | |
678 | "carrier on," so if a driver does not support netif_carrier, | |
679 | it will appear as if the link is always up. In this case, | |
680 | setting use_carrier to 0 will cause bonding to revert to the | |
681 | MII / ETHTOOL ioctl method to determine the link state. | |
682 | ||
683 | A value of 1 enables the use of netif_carrier_ok(), a value of | |
684 | 0 will use the deprecated MII / ETHTOOL ioctls. The default | |
685 | value is 1. | |
686 | ||
00354cfb JV |
687 | xmit_hash_policy |
688 | ||
689 | Selects the transmit hash policy to use for slave selection in | |
690 | balance-xor and 802.3ad modes. Possible values are: | |
691 | ||
692 | layer2 | |
693 | ||
694 | Uses XOR of hardware MAC addresses to generate the | |
695 | hash. The formula is | |
696 | ||
697 | (source MAC XOR destination MAC) modulo slave count | |
698 | ||
699 | This algorithm will place all traffic to a particular | |
700 | network peer on the same slave. | |
701 | ||
702 | This algorithm is 802.3ad compliant. | |
703 | ||
6f6652be JV |
704 | layer2+3 |
705 | ||
706 | This policy uses a combination of layer2 and layer3 | |
707 | protocol information to generate the hash. | |
708 | ||
709 | Uses XOR of hardware MAC addresses and IP addresses to | |
710 | generate the hash. The formula is | |
711 | ||
712 | (((source IP XOR dest IP) AND 0xffff) XOR | |
713 | ( source MAC XOR destination MAC )) | |
714 | modulo slave count | |
715 | ||
716 | This algorithm will place all traffic to a particular | |
717 | network peer on the same slave. For non-IP traffic, | |
718 | the formula is the same as for the layer2 transmit | |
719 | hash policy. | |
720 | ||
721 | This policy is intended to provide a more balanced | |
722 | distribution of traffic than layer2 alone, especially | |
723 | in environments where a layer3 gateway device is | |
724 | required to reach most destinations. | |
725 | ||
d9195881 | 726 | This algorithm is 802.3ad compliant. |
6f6652be | 727 | |
00354cfb JV |
728 | layer3+4 |
729 | ||
730 | This policy uses upper layer protocol information, | |
731 | when available, to generate the hash. This allows for | |
732 | traffic to a particular network peer to span multiple | |
733 | slaves, although a single connection will not span | |
734 | multiple slaves. | |
735 | ||
736 | The formula for unfragmented TCP and UDP packets is | |
737 | ||
738 | ((source port XOR dest port) XOR | |
739 | ((source IP XOR dest IP) AND 0xffff) | |
740 | modulo slave count | |
741 | ||
742 | For fragmented TCP or UDP packets and all other IP | |
743 | protocol traffic, the source and destination port | |
744 | information is omitted. For non-IP traffic, the | |
745 | formula is the same as for the layer2 transmit hash | |
746 | policy. | |
747 | ||
748 | This policy is intended to mimic the behavior of | |
749 | certain switches, notably Cisco switches with PFC2 as | |
750 | well as some Foundry and IBM products. | |
751 | ||
752 | This algorithm is not fully 802.3ad compliant. A | |
753 | single TCP or UDP conversation containing both | |
754 | fragmented and unfragmented packets will see packets | |
755 | striped across two interfaces. This may result in out | |
756 | of order delivery. Most traffic types will not meet | |
757 | this criteria, as TCP rarely fragments traffic, and | |
758 | most UDP traffic is not involved in extended | |
759 | conversations. Other implementations of 802.3ad may | |
760 | or may not tolerate this noncompliance. | |
761 | ||
762 | The default value is layer2. This option was added in bonding | |
6f6652be JV |
763 | version 2.6.3. In earlier versions of bonding, this parameter |
764 | does not exist, and the layer2 policy is the only policy. The | |
765 | layer2+3 value was added for bonding version 3.2.2. | |
1da177e4 LT |
766 | |
767 | ||
768 | 3. Configuring Bonding Devices | |
769 | ============================== | |
770 | ||
6224e01d AK |
771 | You can configure bonding using either your distro's network |
772 | initialization scripts, or manually using either ifenslave or the | |
773 | sysfs interface. Distros generally use one of two packages for the | |
774 | network initialization scripts: initscripts or sysconfig. Recent | |
775 | versions of these packages have support for bonding, while older | |
776 | versions do not. | |
1da177e4 LT |
777 | |
778 | We will first describe the options for configuring bonding for | |
779 | distros using versions of initscripts and sysconfig with full or | |
780 | partial support for bonding, then provide information on enabling | |
781 | bonding without support from the network initialization scripts (i.e., | |
782 | older versions of initscripts or sysconfig). | |
783 | ||
784 | If you're unsure whether your distro uses sysconfig or | |
785 | initscripts, or don't know if it's new enough, have no fear. | |
786 | Determining this is fairly straightforward. | |
787 | ||
788 | First, issue the command: | |
789 | ||
790 | $ rpm -qf /sbin/ifup | |
791 | ||
792 | It will respond with a line of text starting with either | |
793 | "initscripts" or "sysconfig," followed by some numbers. This is the | |
794 | package that provides your network initialization scripts. | |
795 | ||
796 | Next, to determine if your installation supports bonding, | |
797 | issue the command: | |
798 | ||
799 | $ grep ifenslave /sbin/ifup | |
800 | ||
801 | If this returns any matches, then your initscripts or | |
802 | sysconfig has support for bonding. | |
803 | ||
6224e01d | 804 | 3.1 Configuration with Sysconfig Support |
1da177e4 LT |
805 | ---------------------------------------- |
806 | ||
807 | This section applies to distros using a version of sysconfig | |
808 | with bonding support, for example, SuSE Linux Enterprise Server 9. | |
809 | ||
810 | SuSE SLES 9's networking configuration system does support | |
811 | bonding, however, at this writing, the YaST system configuration | |
6224e01d | 812 | front end does not provide any means to work with bonding devices. |
1da177e4 LT |
813 | Bonding devices can be managed by hand, however, as follows. |
814 | ||
815 | First, if they have not already been configured, configure the | |
816 | slave devices. On SLES 9, this is most easily done by running the | |
817 | yast2 sysconfig configuration utility. The goal is for to create an | |
818 | ifcfg-id file for each slave device. The simplest way to accomplish | |
00354cfb JV |
819 | this is to configure the devices for DHCP (this is only to get the |
820 | file ifcfg-id file created; see below for some issues with DHCP). The | |
821 | name of the configuration file for each device will be of the form: | |
1da177e4 LT |
822 | |
823 | ifcfg-id-xx:xx:xx:xx:xx:xx | |
824 | ||
825 | Where the "xx" portion will be replaced with the digits from | |
826 | the device's permanent MAC address. | |
827 | ||
828 | Once the set of ifcfg-id-xx:xx:xx:xx:xx:xx files has been | |
829 | created, it is necessary to edit the configuration files for the slave | |
830 | devices (the MAC addresses correspond to those of the slave devices). | |
00354cfb | 831 | Before editing, the file will contain multiple lines, and will look |
1da177e4 LT |
832 | something like this: |
833 | ||
834 | BOOTPROTO='dhcp' | |
835 | STARTMODE='on' | |
836 | USERCTL='no' | |
837 | UNIQUE='XNzu.WeZGOGF+4wE' | |
838 | _nm_name='bus-pci-0001:61:01.0' | |
839 | ||
840 | Change the BOOTPROTO and STARTMODE lines to the following: | |
841 | ||
842 | BOOTPROTO='none' | |
843 | STARTMODE='off' | |
844 | ||
845 | Do not alter the UNIQUE or _nm_name lines. Remove any other | |
846 | lines (USERCTL, etc). | |
847 | ||
848 | Once the ifcfg-id-xx:xx:xx:xx:xx:xx files have been modified, | |
849 | it's time to create the configuration file for the bonding device | |
850 | itself. This file is named ifcfg-bondX, where X is the number of the | |
851 | bonding device to create, starting at 0. The first such file is | |
852 | ifcfg-bond0, the second is ifcfg-bond1, and so on. The sysconfig | |
853 | network configuration system will correctly start multiple instances | |
854 | of bonding. | |
855 | ||
856 | The contents of the ifcfg-bondX file is as follows: | |
857 | ||
858 | BOOTPROTO="static" | |
859 | BROADCAST="10.0.2.255" | |
860 | IPADDR="10.0.2.10" | |
861 | NETMASK="255.255.0.0" | |
862 | NETWORK="10.0.2.0" | |
863 | REMOTE_IPADDR="" | |
864 | STARTMODE="onboot" | |
865 | BONDING_MASTER="yes" | |
866 | BONDING_MODULE_OPTS="mode=active-backup miimon=100" | |
867 | BONDING_SLAVE0="eth0" | |
00354cfb | 868 | BONDING_SLAVE1="bus-pci-0000:06:08.1" |
1da177e4 LT |
869 | |
870 | Replace the sample BROADCAST, IPADDR, NETMASK and NETWORK | |
871 | values with the appropriate values for your network. | |
872 | ||
1da177e4 LT |
873 | The STARTMODE specifies when the device is brought online. |
874 | The possible values are: | |
875 | ||
876 | onboot: The device is started at boot time. If you're not | |
877 | sure, this is probably what you want. | |
878 | ||
879 | manual: The device is started only when ifup is called | |
880 | manually. Bonding devices may be configured this | |
881 | way if you do not wish them to start automatically | |
882 | at boot for some reason. | |
883 | ||
884 | hotplug: The device is started by a hotplug event. This is not | |
885 | a valid choice for a bonding device. | |
886 | ||
887 | off or ignore: The device configuration is ignored. | |
888 | ||
889 | The line BONDING_MASTER='yes' indicates that the device is a | |
890 | bonding master device. The only useful value is "yes." | |
891 | ||
892 | The contents of BONDING_MODULE_OPTS are supplied to the | |
893 | instance of the bonding module for this device. Specify the options | |
894 | for the bonding mode, link monitoring, and so on here. Do not include | |
895 | the max_bonds bonding parameter; this will confuse the configuration | |
896 | system if you have multiple bonding devices. | |
897 | ||
00354cfb JV |
898 | Finally, supply one BONDING_SLAVEn="slave device" for each |
899 | slave. where "n" is an increasing value, one for each slave. The | |
900 | "slave device" is either an interface name, e.g., "eth0", or a device | |
901 | specifier for the network device. The interface name is easier to | |
902 | find, but the ethN names are subject to change at boot time if, e.g., | |
903 | a device early in the sequence has failed. The device specifiers | |
904 | (bus-pci-0000:06:08.1 in the example above) specify the physical | |
905 | network device, and will not change unless the device's bus location | |
906 | changes (for example, it is moved from one PCI slot to another). The | |
907 | example above uses one of each type for demonstration purposes; most | |
908 | configurations will choose one or the other for all slave devices. | |
1da177e4 LT |
909 | |
910 | When all configuration files have been modified or created, | |
911 | networking must be restarted for the configuration changes to take | |
912 | effect. This can be accomplished via the following: | |
913 | ||
914 | # /etc/init.d/network restart | |
915 | ||
916 | Note that the network control script (/sbin/ifdown) will | |
917 | remove the bonding module as part of the network shutdown processing, | |
918 | so it is not necessary to remove the module by hand if, e.g., the | |
00354cfb | 919 | module parameters have changed. |
1da177e4 LT |
920 | |
921 | Also, at this writing, YaST/YaST2 will not manage bonding | |
922 | devices (they do not show bonding interfaces on its list of network | |
923 | devices). It is necessary to edit the configuration file by hand to | |
924 | change the bonding configuration. | |
925 | ||
926 | Additional general options and details of the ifcfg file | |
927 | format can be found in an example ifcfg template file: | |
928 | ||
929 | /etc/sysconfig/network/ifcfg.template | |
930 | ||
931 | Note that the template does not document the various BONDING_ | |
932 | settings described above, but does describe many of the other options. | |
933 | ||
6224e01d | 934 | 3.1.1 Using DHCP with Sysconfig |
00354cfb JV |
935 | ------------------------------- |
936 | ||
937 | Under sysconfig, configuring a device with BOOTPROTO='dhcp' | |
938 | will cause it to query DHCP for its IP address information. At this | |
939 | writing, this does not function for bonding devices; the scripts | |
940 | attempt to obtain the device address from DHCP prior to adding any of | |
941 | the slave devices. Without active slaves, the DHCP requests are not | |
942 | sent to the network. | |
943 | ||
6224e01d | 944 | 3.1.2 Configuring Multiple Bonds with Sysconfig |
00354cfb JV |
945 | ----------------------------------------------- |
946 | ||
947 | The sysconfig network initialization system is capable of | |
948 | handling multiple bonding devices. All that is necessary is for each | |
949 | bonding instance to have an appropriately configured ifcfg-bondX file | |
950 | (as described above). Do not specify the "max_bonds" parameter to any | |
951 | instance of bonding, as this will confuse sysconfig. If you require | |
952 | multiple bonding devices with identical parameters, create multiple | |
953 | ifcfg-bondX files. | |
954 | ||
955 | Because the sysconfig scripts supply the bonding module | |
956 | options in the ifcfg-bondX file, it is not necessary to add them to | |
957 | the system /etc/modules.conf or /etc/modprobe.conf configuration file. | |
958 | ||
6224e01d | 959 | 3.2 Configuration with Initscripts Support |
1da177e4 LT |
960 | ------------------------------------------ |
961 | ||
9a6c6867 JV |
962 | This section applies to distros using a recent version of |
963 | initscripts with bonding support, for example, Red Hat Enterprise Linux | |
964 | version 3 or later, Fedora, etc. On these systems, the network | |
965 | initialization scripts have knowledge of bonding, and can be configured to | |
966 | control bonding devices. Note that older versions of the initscripts | |
967 | package have lower levels of support for bonding; this will be noted where | |
968 | applicable. | |
1da177e4 LT |
969 | |
970 | These distros will not automatically load the network adapter | |
971 | driver unless the ethX device is configured with an IP address. | |
972 | Because of this constraint, users must manually configure a | |
973 | network-script file for all physical adapters that will be members of | |
974 | a bondX link. Network script files are located in the directory: | |
975 | ||
976 | /etc/sysconfig/network-scripts | |
977 | ||
978 | The file name must be prefixed with "ifcfg-eth" and suffixed | |
979 | with the adapter's physical adapter number. For example, the script | |
980 | for eth0 would be named /etc/sysconfig/network-scripts/ifcfg-eth0. | |
981 | Place the following text in the file: | |
982 | ||
983 | DEVICE=eth0 | |
984 | USERCTL=no | |
985 | ONBOOT=yes | |
986 | MASTER=bond0 | |
987 | SLAVE=yes | |
988 | BOOTPROTO=none | |
989 | ||
990 | The DEVICE= line will be different for every ethX device and | |
991 | must correspond with the name of the file, i.e., ifcfg-eth1 must have | |
992 | a device line of DEVICE=eth1. The setting of the MASTER= line will | |
993 | also depend on the final bonding interface name chosen for your bond. | |
994 | As with other network devices, these typically start at 0, and go up | |
995 | one for each device, i.e., the first bonding instance is bond0, the | |
996 | second is bond1, and so on. | |
997 | ||
998 | Next, create a bond network script. The file name for this | |
999 | script will be /etc/sysconfig/network-scripts/ifcfg-bondX where X is | |
1000 | the number of the bond. For bond0 the file is named "ifcfg-bond0", | |
1001 | for bond1 it is named "ifcfg-bond1", and so on. Within that file, | |
1002 | place the following text: | |
1003 | ||
1004 | DEVICE=bond0 | |
1005 | IPADDR=192.168.1.1 | |
1006 | NETMASK=255.255.255.0 | |
1007 | NETWORK=192.168.1.0 | |
1008 | BROADCAST=192.168.1.255 | |
1009 | ONBOOT=yes | |
1010 | BOOTPROTO=none | |
1011 | USERCTL=no | |
1012 | ||
1013 | Be sure to change the networking specific lines (IPADDR, | |
1014 | NETMASK, NETWORK and BROADCAST) to match your network configuration. | |
1015 | ||
9a6c6867 | 1016 | For later versions of initscripts, such as that found with Fedora |
3f8b4b13 AG |
1017 | 7 (or later) and Red Hat Enterprise Linux version 5 (or later), it is possible, |
1018 | and, indeed, preferable, to specify the bonding options in the ifcfg-bond0 | |
9a6c6867 JV |
1019 | file, e.g. a line of the format: |
1020 | ||
3f8b4b13 | 1021 | BONDING_OPTS="mode=active-backup arp_interval=60 arp_ip_target=192.168.1.254" |
9a6c6867 JV |
1022 | |
1023 | will configure the bond with the specified options. The options | |
1024 | specified in BONDING_OPTS are identical to the bonding module parameters | |
3f8b4b13 AG |
1025 | except for the arp_ip_target field when using versions of initscripts older |
1026 | than and 8.57 (Fedora 8) and 8.45.19 (Red Hat Enterprise Linux 5.2). When | |
1027 | using older versions each target should be included as a separate option and | |
1028 | should be preceded by a '+' to indicate it should be added to the list of | |
1029 | queried targets, e.g., | |
9a6c6867 JV |
1030 | |
1031 | arp_ip_target=+192.168.1.1 arp_ip_target=+192.168.1.2 | |
1032 | ||
1033 | is the proper syntax to specify multiple targets. When specifying | |
1034 | options via BONDING_OPTS, it is not necessary to edit /etc/modules.conf or | |
1035 | /etc/modprobe.conf. | |
1036 | ||
3f8b4b13 | 1037 | For even older versions of initscripts that do not support |
9a6c6867 JV |
1038 | BONDING_OPTS, it is necessary to edit /etc/modules.conf (or |
1039 | /etc/modprobe.conf, depending upon your distro) to load the bonding module | |
1040 | with your desired options when the bond0 interface is brought up. The | |
1041 | following lines in /etc/modules.conf (or modprobe.conf) will load the | |
1042 | bonding module, and select its options: | |
1da177e4 LT |
1043 | |
1044 | alias bond0 bonding | |
1045 | options bond0 mode=balance-alb miimon=100 | |
1046 | ||
1047 | Replace the sample parameters with the appropriate set of | |
1048 | options for your configuration. | |
1049 | ||
1050 | Finally run "/etc/rc.d/init.d/network restart" as root. This | |
1051 | will restart the networking subsystem and your bond link should be now | |
1052 | up and running. | |
1053 | ||
6224e01d | 1054 | 3.2.1 Using DHCP with Initscripts |
00354cfb JV |
1055 | --------------------------------- |
1056 | ||
9a6c6867 JV |
1057 | Recent versions of initscripts (the versions supplied with Fedora |
1058 | Core 3 and Red Hat Enterprise Linux 4, or later versions, are reported to | |
1059 | work) have support for assigning IP information to bonding devices via | |
1060 | DHCP. | |
00354cfb JV |
1061 | |
1062 | To configure bonding for DHCP, configure it as described | |
1063 | above, except replace the line "BOOTPROTO=none" with "BOOTPROTO=dhcp" | |
1064 | and add a line consisting of "TYPE=Bonding". Note that the TYPE value | |
1065 | is case sensitive. | |
1066 | ||
6224e01d | 1067 | 3.2.2 Configuring Multiple Bonds with Initscripts |
00354cfb JV |
1068 | ------------------------------------------------- |
1069 | ||
9a6c6867 JV |
1070 | Initscripts packages that are included with Fedora 7 and Red Hat |
1071 | Enterprise Linux 5 support multiple bonding interfaces by simply | |
1072 | specifying the appropriate BONDING_OPTS= in ifcfg-bondX where X is the | |
1073 | number of the bond. This support requires sysfs support in the kernel, | |
1074 | and a bonding driver of version 3.0.0 or later. Other configurations may | |
1075 | not support this method for specifying multiple bonding interfaces; for | |
1076 | those instances, see the "Configuring Multiple Bonds Manually" section, | |
1077 | below. | |
1da177e4 | 1078 | |
6224e01d AK |
1079 | 3.3 Configuring Bonding Manually with Ifenslave |
1080 | ----------------------------------------------- | |
1da177e4 LT |
1081 | |
1082 | This section applies to distros whose network initialization | |
1083 | scripts (the sysconfig or initscripts package) do not have specific | |
1084 | knowledge of bonding. One such distro is SuSE Linux Enterprise Server | |
1085 | version 8. | |
1086 | ||
00354cfb JV |
1087 | The general method for these systems is to place the bonding |
1088 | module parameters into /etc/modules.conf or /etc/modprobe.conf (as | |
1089 | appropriate for the installed distro), then add modprobe and/or | |
1090 | ifenslave commands to the system's global init script. The name of | |
1091 | the global init script differs; for sysconfig, it is | |
1da177e4 LT |
1092 | /etc/init.d/boot.local and for initscripts it is /etc/rc.d/rc.local. |
1093 | ||
1094 | For example, if you wanted to make a simple bond of two e100 | |
1095 | devices (presumed to be eth0 and eth1), and have it persist across | |
1096 | reboots, edit the appropriate file (/etc/init.d/boot.local or | |
1097 | /etc/rc.d/rc.local), and add the following: | |
1098 | ||
00354cfb | 1099 | modprobe bonding mode=balance-alb miimon=100 |
1da177e4 LT |
1100 | modprobe e100 |
1101 | ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up | |
1102 | ifenslave bond0 eth0 | |
1103 | ifenslave bond0 eth1 | |
1104 | ||
1105 | Replace the example bonding module parameters and bond0 | |
1106 | network configuration (IP address, netmask, etc) with the appropriate | |
00354cfb | 1107 | values for your configuration. |
1da177e4 LT |
1108 | |
1109 | Unfortunately, this method will not provide support for the | |
1110 | ifup and ifdown scripts on the bond devices. To reload the bonding | |
1111 | configuration, it is necessary to run the initialization script, e.g., | |
1112 | ||
1113 | # /etc/init.d/boot.local | |
1114 | ||
1115 | or | |
1116 | ||
1117 | # /etc/rc.d/rc.local | |
1118 | ||
1119 | It may be desirable in such a case to create a separate script | |
1120 | which only initializes the bonding configuration, then call that | |
1121 | separate script from within boot.local. This allows for bonding to be | |
1122 | enabled without re-running the entire global init script. | |
1123 | ||
1124 | To shut down the bonding devices, it is necessary to first | |
1125 | mark the bonding device itself as being down, then remove the | |
1126 | appropriate device driver modules. For our example above, you can do | |
1127 | the following: | |
1128 | ||
1129 | # ifconfig bond0 down | |
00354cfb | 1130 | # rmmod bonding |
1da177e4 LT |
1131 | # rmmod e100 |
1132 | ||
1133 | Again, for convenience, it may be desirable to create a script | |
1134 | with these commands. | |
1135 | ||
1136 | ||
00354cfb JV |
1137 | 3.3.1 Configuring Multiple Bonds Manually |
1138 | ----------------------------------------- | |
1da177e4 LT |
1139 | |
1140 | This section contains information on configuring multiple | |
00354cfb JV |
1141 | bonding devices with differing options for those systems whose network |
1142 | initialization scripts lack support for configuring multiple bonds. | |
1143 | ||
1144 | If you require multiple bonding devices, but all with the same | |
1145 | options, you may wish to use the "max_bonds" module parameter, | |
1146 | documented above. | |
1da177e4 | 1147 | |
9a6c6867 JV |
1148 | To create multiple bonding devices with differing options, it is |
1149 | preferrable to use bonding parameters exported by sysfs, documented in the | |
1150 | section below. | |
1151 | ||
1152 | For versions of bonding without sysfs support, the only means to | |
1153 | provide multiple instances of bonding with differing options is to load | |
1154 | the bonding driver multiple times. Note that current versions of the | |
1155 | sysconfig network initialization scripts handle this automatically; if | |
1156 | your distro uses these scripts, no special action is needed. See the | |
1157 | section Configuring Bonding Devices, above, if you're not sure about your | |
1158 | network initialization scripts. | |
1159 | ||
1160 | To load multiple instances of the module, it is necessary to | |
1161 | specify a different name for each instance (the module loading system | |
1162 | requires that every loaded module, even multiple instances of the same | |
1163 | module, have a unique name). This is accomplished by supplying multiple | |
1164 | sets of bonding options in /etc/modprobe.conf, for example: | |
1165 | ||
1166 | alias bond0 bonding | |
1167 | options bond0 -o bond0 mode=balance-rr miimon=100 | |
1168 | ||
1169 | alias bond1 bonding | |
1170 | options bond1 -o bond1 mode=balance-alb miimon=50 | |
1171 | ||
1172 | will load the bonding module two times. The first instance is | |
1173 | named "bond0" and creates the bond0 device in balance-rr mode with an | |
1174 | miimon of 100. The second instance is named "bond1" and creates the | |
1175 | bond1 device in balance-alb mode with an miimon of 50. | |
1176 | ||
1177 | In some circumstances (typically with older distributions), | |
1178 | the above does not work, and the second bonding instance never sees | |
1179 | its options. In that case, the second options line can be substituted | |
1180 | as follows: | |
1181 | ||
1182 | install bond1 /sbin/modprobe --ignore-install bonding -o bond1 \ | |
1183 | mode=balance-alb miimon=50 | |
00354cfb | 1184 | |
9a6c6867 JV |
1185 | This may be repeated any number of times, specifying a new and |
1186 | unique name in place of bond1 for each subsequent instance. | |
1187 | ||
1188 | It has been observed that some Red Hat supplied kernels are unable | |
1189 | to rename modules at load time (the "-o bond1" part). Attempts to pass | |
1190 | that option to modprobe will produce an "Operation not permitted" error. | |
1191 | This has been reported on some Fedora Core kernels, and has been seen on | |
1192 | RHEL 4 as well. On kernels exhibiting this problem, it will be impossible | |
1193 | to configure multiple bonds with differing parameters (as they are older | |
1194 | kernels, and also lack sysfs support). | |
1da177e4 | 1195 | |
6224e01d AK |
1196 | 3.4 Configuring Bonding Manually via Sysfs |
1197 | ------------------------------------------ | |
1198 | ||
9a6c6867 | 1199 | Starting with version 3.0.0, Channel Bonding may be configured |
6224e01d AK |
1200 | via the sysfs interface. This interface allows dynamic configuration |
1201 | of all bonds in the system without unloading the module. It also | |
1202 | allows for adding and removing bonds at runtime. Ifenslave is no | |
1203 | longer required, though it is still supported. | |
1204 | ||
1205 | Use of the sysfs interface allows you to use multiple bonds | |
1206 | with different configurations without having to reload the module. | |
1207 | It also allows you to use multiple, differently configured bonds when | |
1208 | bonding is compiled into the kernel. | |
1209 | ||
1210 | You must have the sysfs filesystem mounted to configure | |
1211 | bonding this way. The examples in this document assume that you | |
1212 | are using the standard mount point for sysfs, e.g. /sys. If your | |
1213 | sysfs filesystem is mounted elsewhere, you will need to adjust the | |
1214 | example paths accordingly. | |
1215 | ||
1216 | Creating and Destroying Bonds | |
1217 | ----------------------------- | |
1218 | To add a new bond foo: | |
1219 | # echo +foo > /sys/class/net/bonding_masters | |
1220 | ||
1221 | To remove an existing bond bar: | |
1222 | # echo -bar > /sys/class/net/bonding_masters | |
1223 | ||
1224 | To show all existing bonds: | |
1225 | # cat /sys/class/net/bonding_masters | |
1226 | ||
1227 | NOTE: due to 4K size limitation of sysfs files, this list may be | |
1228 | truncated if you have more than a few hundred bonds. This is unlikely | |
1229 | to occur under normal operating conditions. | |
1230 | ||
1231 | Adding and Removing Slaves | |
1232 | -------------------------- | |
1233 | Interfaces may be enslaved to a bond using the file | |
1234 | /sys/class/net/<bond>/bonding/slaves. The semantics for this file | |
1235 | are the same as for the bonding_masters file. | |
1236 | ||
1237 | To enslave interface eth0 to bond bond0: | |
1238 | # ifconfig bond0 up | |
1239 | # echo +eth0 > /sys/class/net/bond0/bonding/slaves | |
1240 | ||
1241 | To free slave eth0 from bond bond0: | |
1242 | # echo -eth0 > /sys/class/net/bond0/bonding/slaves | |
1243 | ||
6224e01d AK |
1244 | When an interface is enslaved to a bond, symlinks between the |
1245 | two are created in the sysfs filesystem. In this case, you would get | |
1246 | /sys/class/net/bond0/slave_eth0 pointing to /sys/class/net/eth0, and | |
1247 | /sys/class/net/eth0/master pointing to /sys/class/net/bond0. | |
1248 | ||
1249 | This means that you can tell quickly whether or not an | |
1250 | interface is enslaved by looking for the master symlink. Thus: | |
1251 | # echo -eth0 > /sys/class/net/eth0/master/bonding/slaves | |
1252 | will free eth0 from whatever bond it is enslaved to, regardless of | |
1253 | the name of the bond interface. | |
1254 | ||
1255 | Changing a Bond's Configuration | |
1256 | ------------------------------- | |
1257 | Each bond may be configured individually by manipulating the | |
1258 | files located in /sys/class/net/<bond name>/bonding | |
1259 | ||
1260 | The names of these files correspond directly with the command- | |
670e9f34 | 1261 | line parameters described elsewhere in this file, and, with the |
6224e01d AK |
1262 | exception of arp_ip_target, they accept the same values. To see the |
1263 | current setting, simply cat the appropriate file. | |
1264 | ||
1265 | A few examples will be given here; for specific usage | |
1266 | guidelines for each parameter, see the appropriate section in this | |
1267 | document. | |
1268 | ||
1269 | To configure bond0 for balance-alb mode: | |
1270 | # ifconfig bond0 down | |
1271 | # echo 6 > /sys/class/net/bond0/bonding/mode | |
1272 | - or - | |
1273 | # echo balance-alb > /sys/class/net/bond0/bonding/mode | |
1274 | NOTE: The bond interface must be down before the mode can be | |
1275 | changed. | |
1276 | ||
1277 | To enable MII monitoring on bond0 with a 1 second interval: | |
1278 | # echo 1000 > /sys/class/net/bond0/bonding/miimon | |
1279 | NOTE: If ARP monitoring is enabled, it will disabled when MII | |
1280 | monitoring is enabled, and vice-versa. | |
1281 | ||
1282 | To add ARP targets: | |
1283 | # echo +192.168.0.100 > /sys/class/net/bond0/bonding/arp_ip_target | |
1284 | # echo +192.168.0.101 > /sys/class/net/bond0/bonding/arp_ip_target | |
5a31bec0 | 1285 | NOTE: up to 16 target addresses may be specified. |
6224e01d AK |
1286 | |
1287 | To remove an ARP target: | |
1288 | # echo -192.168.0.100 > /sys/class/net/bond0/bonding/arp_ip_target | |
1289 | ||
1290 | Example Configuration | |
1291 | --------------------- | |
1292 | We begin with the same example that is shown in section 3.3, | |
1293 | executed with sysfs, and without using ifenslave. | |
1294 | ||
1295 | To make a simple bond of two e100 devices (presumed to be eth0 | |
1296 | and eth1), and have it persist across reboots, edit the appropriate | |
1297 | file (/etc/init.d/boot.local or /etc/rc.d/rc.local), and add the | |
1298 | following: | |
1299 | ||
1300 | modprobe bonding | |
1301 | modprobe e100 | |
1302 | echo balance-alb > /sys/class/net/bond0/bonding/mode | |
1303 | ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up | |
1304 | echo 100 > /sys/class/net/bond0/bonding/miimon | |
1305 | echo +eth0 > /sys/class/net/bond0/bonding/slaves | |
1306 | echo +eth1 > /sys/class/net/bond0/bonding/slaves | |
1307 | ||
1308 | To add a second bond, with two e1000 interfaces in | |
1309 | active-backup mode, using ARP monitoring, add the following lines to | |
1310 | your init script: | |
1311 | ||
1312 | modprobe e1000 | |
1313 | echo +bond1 > /sys/class/net/bonding_masters | |
1314 | echo active-backup > /sys/class/net/bond1/bonding/mode | |
1315 | ifconfig bond1 192.168.2.1 netmask 255.255.255.0 up | |
1316 | echo +192.168.2.100 /sys/class/net/bond1/bonding/arp_ip_target | |
1317 | echo 2000 > /sys/class/net/bond1/bonding/arp_interval | |
1318 | echo +eth2 > /sys/class/net/bond1/bonding/slaves | |
1319 | echo +eth3 > /sys/class/net/bond1/bonding/slaves | |
1320 | ||
1da177e4 | 1321 | |
6224e01d | 1322 | 4. Querying Bonding Configuration |
1da177e4 LT |
1323 | ================================= |
1324 | ||
6224e01d | 1325 | 4.1 Bonding Configuration |
1da177e4 LT |
1326 | ------------------------- |
1327 | ||
1328 | Each bonding device has a read-only file residing in the | |
1329 | /proc/net/bonding directory. The file contents include information | |
1330 | about the bonding configuration, options and state of each slave. | |
1331 | ||
1332 | For example, the contents of /proc/net/bonding/bond0 after the | |
1333 | driver is loaded with parameters of mode=0 and miimon=1000 is | |
1334 | generally as follows: | |
1335 | ||
1336 | Ethernet Channel Bonding Driver: 2.6.1 (October 29, 2004) | |
1337 | Bonding Mode: load balancing (round-robin) | |
1338 | Currently Active Slave: eth0 | |
1339 | MII Status: up | |
1340 | MII Polling Interval (ms): 1000 | |
1341 | Up Delay (ms): 0 | |
1342 | Down Delay (ms): 0 | |
1343 | ||
1344 | Slave Interface: eth1 | |
1345 | MII Status: up | |
1346 | Link Failure Count: 1 | |
1347 | ||
1348 | Slave Interface: eth0 | |
1349 | MII Status: up | |
1350 | Link Failure Count: 1 | |
1351 | ||
1352 | The precise format and contents will change depending upon the | |
1353 | bonding configuration, state, and version of the bonding driver. | |
1354 | ||
6224e01d | 1355 | 4.2 Network configuration |
1da177e4 LT |
1356 | ------------------------- |
1357 | ||
1358 | The network configuration can be inspected using the ifconfig | |
1359 | command. Bonding devices will have the MASTER flag set; Bonding slave | |
1360 | devices will have the SLAVE flag set. The ifconfig output does not | |
1361 | contain information on which slaves are associated with which masters. | |
1362 | ||
1363 | In the example below, the bond0 interface is the master | |
1364 | (MASTER) while eth0 and eth1 are slaves (SLAVE). Notice all slaves of | |
1365 | bond0 have the same MAC address (HWaddr) as bond0 for all modes except | |
1366 | TLB and ALB that require a unique MAC address for each slave. | |
1367 | ||
1368 | # /sbin/ifconfig | |
1369 | bond0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4 | |
1370 | inet addr:XXX.XXX.XXX.YYY Bcast:XXX.XXX.XXX.255 Mask:255.255.252.0 | |
1371 | UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1 | |
1372 | RX packets:7224794 errors:0 dropped:0 overruns:0 frame:0 | |
1373 | TX packets:3286647 errors:1 dropped:0 overruns:1 carrier:0 | |
1374 | collisions:0 txqueuelen:0 | |
1375 | ||
1376 | eth0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4 | |
1da177e4 LT |
1377 | UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1 |
1378 | RX packets:3573025 errors:0 dropped:0 overruns:0 frame:0 | |
1379 | TX packets:1643167 errors:1 dropped:0 overruns:1 carrier:0 | |
1380 | collisions:0 txqueuelen:100 | |
1381 | Interrupt:10 Base address:0x1080 | |
1382 | ||
1383 | eth1 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4 | |
1da177e4 LT |
1384 | UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1 |
1385 | RX packets:3651769 errors:0 dropped:0 overruns:0 frame:0 | |
1386 | TX packets:1643480 errors:0 dropped:0 overruns:0 carrier:0 | |
1387 | collisions:0 txqueuelen:100 | |
1388 | Interrupt:9 Base address:0x1400 | |
1389 | ||
6224e01d | 1390 | 5. Switch Configuration |
1da177e4 LT |
1391 | ======================= |
1392 | ||
1393 | For this section, "switch" refers to whatever system the | |
1394 | bonded devices are directly connected to (i.e., where the other end of | |
1395 | the cable plugs into). This may be an actual dedicated switch device, | |
1396 | or it may be another regular system (e.g., another computer running | |
1397 | Linux), | |
1398 | ||
1399 | The active-backup, balance-tlb and balance-alb modes do not | |
1400 | require any specific configuration of the switch. | |
1401 | ||
1402 | The 802.3ad mode requires that the switch have the appropriate | |
1403 | ports configured as an 802.3ad aggregation. The precise method used | |
1404 | to configure this varies from switch to switch, but, for example, a | |
1405 | Cisco 3550 series switch requires that the appropriate ports first be | |
1406 | grouped together in a single etherchannel instance, then that | |
1407 | etherchannel is set to mode "lacp" to enable 802.3ad (instead of | |
1408 | standard EtherChannel). | |
1409 | ||
1410 | The balance-rr, balance-xor and broadcast modes generally | |
1411 | require that the switch have the appropriate ports grouped together. | |
1412 | The nomenclature for such a group differs between switches, it may be | |
1413 | called an "etherchannel" (as in the Cisco example, above), a "trunk | |
1414 | group" or some other similar variation. For these modes, each switch | |
1415 | will also have its own configuration options for the switch's transmit | |
1416 | policy to the bond. Typical choices include XOR of either the MAC or | |
1417 | IP addresses. The transmit policy of the two peers does not need to | |
1418 | match. For these three modes, the bonding mode really selects a | |
1419 | transmit policy for an EtherChannel group; all three will interoperate | |
1420 | with another EtherChannel group. | |
1421 | ||
1422 | ||
6224e01d | 1423 | 6. 802.1q VLAN Support |
1da177e4 LT |
1424 | ====================== |
1425 | ||
1426 | It is possible to configure VLAN devices over a bond interface | |
1427 | using the 8021q driver. However, only packets coming from the 8021q | |
1428 | driver and passing through bonding will be tagged by default. Self | |
1429 | generated packets, for example, bonding's learning packets or ARP | |
1430 | packets generated by either ALB mode or the ARP monitor mechanism, are | |
1431 | tagged internally by bonding itself. As a result, bonding must | |
1432 | "learn" the VLAN IDs configured above it, and use those IDs to tag | |
1433 | self generated packets. | |
1434 | ||
1435 | For reasons of simplicity, and to support the use of adapters | |
00354cfb JV |
1436 | that can do VLAN hardware acceleration offloading, the bonding |
1437 | interface declares itself as fully hardware offloading capable, it gets | |
1da177e4 LT |
1438 | the add_vid/kill_vid notifications to gather the necessary |
1439 | information, and it propagates those actions to the slaves. In case | |
1440 | of mixed adapter types, hardware accelerated tagged packets that | |
1441 | should go through an adapter that is not offloading capable are | |
1442 | "un-accelerated" by the bonding driver so the VLAN tag sits in the | |
1443 | regular location. | |
1444 | ||
1445 | VLAN interfaces *must* be added on top of a bonding interface | |
1446 | only after enslaving at least one slave. The bonding interface has a | |
1447 | hardware address of 00:00:00:00:00:00 until the first slave is added. | |
1448 | If the VLAN interface is created prior to the first enslavement, it | |
1449 | would pick up the all-zeroes hardware address. Once the first slave | |
1450 | is attached to the bond, the bond device itself will pick up the | |
1451 | slave's hardware address, which is then available for the VLAN device. | |
1452 | ||
1453 | Also, be aware that a similar problem can occur if all slaves | |
1454 | are released from a bond that still has one or more VLAN interfaces on | |
1455 | top of it. When a new slave is added, the bonding interface will | |
1456 | obtain its hardware address from the first slave, which might not | |
1457 | match the hardware address of the VLAN interfaces (which was | |
1458 | ultimately copied from an earlier slave). | |
1459 | ||
1460 | There are two methods to insure that the VLAN device operates | |
1461 | with the correct hardware address if all slaves are removed from a | |
1462 | bond interface: | |
1463 | ||
1464 | 1. Remove all VLAN interfaces then recreate them | |
1465 | ||
1466 | 2. Set the bonding interface's hardware address so that it | |
1467 | matches the hardware address of the VLAN interfaces. | |
1468 | ||
1469 | Note that changing a VLAN interface's HW address would set the | |
00354cfb | 1470 | underlying device -- i.e. the bonding interface -- to promiscuous |
1da177e4 LT |
1471 | mode, which might not be what you want. |
1472 | ||
1473 | ||
6224e01d | 1474 | 7. Link Monitoring |
1da177e4 LT |
1475 | ================== |
1476 | ||
1477 | The bonding driver at present supports two schemes for | |
1478 | monitoring a slave device's link state: the ARP monitor and the MII | |
1479 | monitor. | |
1480 | ||
1481 | At the present time, due to implementation restrictions in the | |
1482 | bonding driver itself, it is not possible to enable both ARP and MII | |
1483 | monitoring simultaneously. | |
1484 | ||
6224e01d | 1485 | 7.1 ARP Monitor Operation |
1da177e4 LT |
1486 | ------------------------- |
1487 | ||
1488 | The ARP monitor operates as its name suggests: it sends ARP | |
1489 | queries to one or more designated peer systems on the network, and | |
1490 | uses the response as an indication that the link is operating. This | |
1491 | gives some assurance that traffic is actually flowing to and from one | |
1492 | or more peers on the local network. | |
1493 | ||
1494 | The ARP monitor relies on the device driver itself to verify | |
1495 | that traffic is flowing. In particular, the driver must keep up to | |
1496 | date the last receive time, dev->last_rx, and transmit start time, | |
1497 | dev->trans_start. If these are not updated by the driver, then the | |
1498 | ARP monitor will immediately fail any slaves using that driver, and | |
1499 | those slaves will stay down. If networking monitoring (tcpdump, etc) | |
1500 | shows the ARP requests and replies on the network, then it may be that | |
1501 | your device driver is not updating last_rx and trans_start. | |
1502 | ||
6224e01d | 1503 | 7.2 Configuring Multiple ARP Targets |
1da177e4 LT |
1504 | ------------------------------------ |
1505 | ||
1506 | While ARP monitoring can be done with just one target, it can | |
1507 | be useful in a High Availability setup to have several targets to | |
1508 | monitor. In the case of just one target, the target itself may go | |
1509 | down or have a problem making it unresponsive to ARP requests. Having | |
1510 | an additional target (or several) increases the reliability of the ARP | |
1511 | monitoring. | |
1512 | ||
00354cfb | 1513 | Multiple ARP targets must be separated by commas as follows: |
1da177e4 LT |
1514 | |
1515 | # example options for ARP monitoring with three targets | |
1516 | alias bond0 bonding | |
1517 | options bond0 arp_interval=60 arp_ip_target=192.168.0.1,192.168.0.3,192.168.0.9 | |
1518 | ||
1519 | For just a single target the options would resemble: | |
1520 | ||
1521 | # example options for ARP monitoring with one target | |
1522 | alias bond0 bonding | |
1523 | options bond0 arp_interval=60 arp_ip_target=192.168.0.100 | |
1524 | ||
1525 | ||
6224e01d | 1526 | 7.3 MII Monitor Operation |
1da177e4 LT |
1527 | ------------------------- |
1528 | ||
1529 | The MII monitor monitors only the carrier state of the local | |
1530 | network interface. It accomplishes this in one of three ways: by | |
1531 | depending upon the device driver to maintain its carrier state, by | |
1532 | querying the device's MII registers, or by making an ethtool query to | |
1533 | the device. | |
1534 | ||
1535 | If the use_carrier module parameter is 1 (the default value), | |
1536 | then the MII monitor will rely on the driver for carrier state | |
1537 | information (via the netif_carrier subsystem). As explained in the | |
1538 | use_carrier parameter information, above, if the MII monitor fails to | |
1539 | detect carrier loss on the device (e.g., when the cable is physically | |
1540 | disconnected), it may be that the driver does not support | |
1541 | netif_carrier. | |
1542 | ||
1543 | If use_carrier is 0, then the MII monitor will first query the | |
1544 | device's (via ioctl) MII registers and check the link state. If that | |
1545 | request fails (not just that it returns carrier down), then the MII | |
1546 | monitor will make an ethtool ETHOOL_GLINK request to attempt to obtain | |
1547 | the same information. If both methods fail (i.e., the driver either | |
1548 | does not support or had some error in processing both the MII register | |
1549 | and ethtool requests), then the MII monitor will assume the link is | |
1550 | up. | |
1551 | ||
6224e01d | 1552 | 8. Potential Sources of Trouble |
1da177e4 LT |
1553 | =============================== |
1554 | ||
6224e01d | 1555 | 8.1 Adventures in Routing |
1da177e4 LT |
1556 | ------------------------- |
1557 | ||
1558 | When bonding is configured, it is important that the slave | |
6224e01d | 1559 | devices not have routes that supersede routes of the master (or, |
1da177e4 LT |
1560 | generally, not have routes at all). For example, suppose the bonding |
1561 | device bond0 has two slaves, eth0 and eth1, and the routing table is | |
1562 | as follows: | |
1563 | ||
1564 | Kernel IP routing table | |
1565 | Destination Gateway Genmask Flags MSS Window irtt Iface | |
1566 | 10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth0 | |
1567 | 10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth1 | |
1568 | 10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 bond0 | |
1569 | 127.0.0.0 0.0.0.0 255.0.0.0 U 40 0 0 lo | |
1570 | ||
1571 | This routing configuration will likely still update the | |
1572 | receive/transmit times in the driver (needed by the ARP monitor), but | |
1573 | may bypass the bonding driver (because outgoing traffic to, in this | |
1574 | case, another host on network 10 would use eth0 or eth1 before bond0). | |
1575 | ||
1576 | The ARP monitor (and ARP itself) may become confused by this | |
1577 | configuration, because ARP requests (generated by the ARP monitor) | |
1578 | will be sent on one interface (bond0), but the corresponding reply | |
1579 | will arrive on a different interface (eth0). This reply looks to ARP | |
1580 | as an unsolicited ARP reply (because ARP matches replies on an | |
1581 | interface basis), and is discarded. The MII monitor is not affected | |
1582 | by the state of the routing table. | |
1583 | ||
1584 | The solution here is simply to insure that slaves do not have | |
1585 | routes of their own, and if for some reason they must, those routes do | |
6224e01d | 1586 | not supersede routes of their master. This should generally be the |
1da177e4 LT |
1587 | case, but unusual configurations or errant manual or automatic static |
1588 | route additions may cause trouble. | |
1589 | ||
6224e01d | 1590 | 8.2 Ethernet Device Renaming |
1da177e4 LT |
1591 | ---------------------------- |
1592 | ||
1593 | On systems with network configuration scripts that do not | |
1594 | associate physical devices directly with network interface names (so | |
1595 | that the same physical device always has the same "ethX" name), it may | |
1596 | be necessary to add some special logic to either /etc/modules.conf or | |
1597 | /etc/modprobe.conf (depending upon which is installed on the system). | |
1598 | ||
1599 | For example, given a modules.conf containing the following: | |
1600 | ||
1601 | alias bond0 bonding | |
1602 | options bond0 mode=some-mode miimon=50 | |
1603 | alias eth0 tg3 | |
1604 | alias eth1 tg3 | |
1605 | alias eth2 e1000 | |
1606 | alias eth3 e1000 | |
1607 | ||
1608 | If neither eth0 and eth1 are slaves to bond0, then when the | |
1609 | bond0 interface comes up, the devices may end up reordered. This | |
1610 | happens because bonding is loaded first, then its slave device's | |
1611 | drivers are loaded next. Since no other drivers have been loaded, | |
1612 | when the e1000 driver loads, it will receive eth0 and eth1 for its | |
1613 | devices, but the bonding configuration tries to enslave eth2 and eth3 | |
1614 | (which may later be assigned to the tg3 devices). | |
1615 | ||
1616 | Adding the following: | |
1617 | ||
1618 | add above bonding e1000 tg3 | |
1619 | ||
1620 | causes modprobe to load e1000 then tg3, in that order, when | |
1621 | bonding is loaded. This command is fully documented in the | |
1622 | modules.conf manual page. | |
1623 | ||
1624 | On systems utilizing modprobe.conf (or modprobe.conf.local), | |
1625 | an equivalent problem can occur. In this case, the following can be | |
1626 | added to modprobe.conf (or modprobe.conf.local, as appropriate), as | |
1627 | follows (all on one line; it has been split here for clarity): | |
1628 | ||
1629 | install bonding /sbin/modprobe tg3; /sbin/modprobe e1000; | |
1630 | /sbin/modprobe --ignore-install bonding | |
1631 | ||
1632 | This will, when loading the bonding module, rather than | |
1633 | performing the normal action, instead execute the provided command. | |
1634 | This command loads the device drivers in the order needed, then calls | |
00354cfb | 1635 | modprobe with --ignore-install to cause the normal action to then take |
1da177e4 LT |
1636 | place. Full documentation on this can be found in the modprobe.conf |
1637 | and modprobe manual pages. | |
1638 | ||
6224e01d | 1639 | 8.3. Painfully Slow Or No Failed Link Detection By Miimon |
1da177e4 LT |
1640 | --------------------------------------------------------- |
1641 | ||
1642 | By default, bonding enables the use_carrier option, which | |
1643 | instructs bonding to trust the driver to maintain carrier state. | |
1644 | ||
1645 | As discussed in the options section, above, some drivers do | |
1646 | not support the netif_carrier_on/_off link state tracking system. | |
1647 | With use_carrier enabled, bonding will always see these links as up, | |
1648 | regardless of their actual state. | |
1649 | ||
1650 | Additionally, other drivers do support netif_carrier, but do | |
1651 | not maintain it in real time, e.g., only polling the link state at | |
1652 | some fixed interval. In this case, miimon will detect failures, but | |
1653 | only after some long period of time has expired. If it appears that | |
1654 | miimon is very slow in detecting link failures, try specifying | |
1655 | use_carrier=0 to see if that improves the failure detection time. If | |
1656 | it does, then it may be that the driver checks the carrier state at a | |
1657 | fixed interval, but does not cache the MII register values (so the | |
1658 | use_carrier=0 method of querying the registers directly works). If | |
1659 | use_carrier=0 does not improve the failover, then the driver may cache | |
1660 | the registers, or the problem may be elsewhere. | |
1661 | ||
1662 | Also, remember that miimon only checks for the device's | |
1663 | carrier state. It has no way to determine the state of devices on or | |
1664 | beyond other ports of a switch, or if a switch is refusing to pass | |
1665 | traffic while still maintaining carrier on. | |
1666 | ||
6224e01d | 1667 | 9. SNMP agents |
1da177e4 LT |
1668 | =============== |
1669 | ||
1670 | If running SNMP agents, the bonding driver should be loaded | |
1671 | before any network drivers participating in a bond. This requirement | |
d533f671 | 1672 | is due to the interface index (ipAdEntIfIndex) being associated to |
1da177e4 LT |
1673 | the first interface found with a given IP address. That is, there is |
1674 | only one ipAdEntIfIndex for each IP address. For example, if eth0 and | |
1675 | eth1 are slaves of bond0 and the driver for eth0 is loaded before the | |
1676 | bonding driver, the interface for the IP address will be associated | |
1677 | with the eth0 interface. This configuration is shown below, the IP | |
1678 | address 192.168.1.1 has an interface index of 2 which indexes to eth0 | |
1679 | in the ifDescr table (ifDescr.2). | |
1680 | ||
1681 | interfaces.ifTable.ifEntry.ifDescr.1 = lo | |
1682 | interfaces.ifTable.ifEntry.ifDescr.2 = eth0 | |
1683 | interfaces.ifTable.ifEntry.ifDescr.3 = eth1 | |
1684 | interfaces.ifTable.ifEntry.ifDescr.4 = eth2 | |
1685 | interfaces.ifTable.ifEntry.ifDescr.5 = eth3 | |
1686 | interfaces.ifTable.ifEntry.ifDescr.6 = bond0 | |
1687 | ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 5 | |
1688 | ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2 | |
1689 | ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 4 | |
1690 | ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1 | |
1691 | ||
1692 | This problem is avoided by loading the bonding driver before | |
1693 | any network drivers participating in a bond. Below is an example of | |
1694 | loading the bonding driver first, the IP address 192.168.1.1 is | |
1695 | correctly associated with ifDescr.2. | |
1696 | ||
1697 | interfaces.ifTable.ifEntry.ifDescr.1 = lo | |
1698 | interfaces.ifTable.ifEntry.ifDescr.2 = bond0 | |
1699 | interfaces.ifTable.ifEntry.ifDescr.3 = eth0 | |
1700 | interfaces.ifTable.ifEntry.ifDescr.4 = eth1 | |
1701 | interfaces.ifTable.ifEntry.ifDescr.5 = eth2 | |
1702 | interfaces.ifTable.ifEntry.ifDescr.6 = eth3 | |
1703 | ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 6 | |
1704 | ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2 | |
1705 | ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 5 | |
1706 | ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1 | |
1707 | ||
1708 | While some distributions may not report the interface name in | |
1709 | ifDescr, the association between the IP address and IfIndex remains | |
1710 | and SNMP functions such as Interface_Scan_Next will report that | |
1711 | association. | |
1712 | ||
6224e01d | 1713 | 10. Promiscuous mode |
1da177e4 LT |
1714 | ==================== |
1715 | ||
1716 | When running network monitoring tools, e.g., tcpdump, it is | |
1717 | common to enable promiscuous mode on the device, so that all traffic | |
1718 | is seen (instead of seeing only traffic destined for the local host). | |
1719 | The bonding driver handles promiscuous mode changes to the bonding | |
00354cfb | 1720 | master device (e.g., bond0), and propagates the setting to the slave |
1da177e4 LT |
1721 | devices. |
1722 | ||
1723 | For the balance-rr, balance-xor, broadcast, and 802.3ad modes, | |
00354cfb | 1724 | the promiscuous mode setting is propagated to all slaves. |
1da177e4 LT |
1725 | |
1726 | For the active-backup, balance-tlb and balance-alb modes, the | |
00354cfb | 1727 | promiscuous mode setting is propagated only to the active slave. |
1da177e4 LT |
1728 | |
1729 | For balance-tlb mode, the active slave is the slave currently | |
1730 | receiving inbound traffic. | |
1731 | ||
1732 | For balance-alb mode, the active slave is the slave used as a | |
1733 | "primary." This slave is used for mode-specific control traffic, for | |
1734 | sending to peers that are unassigned or if the load is unbalanced. | |
1735 | ||
1736 | For the active-backup, balance-tlb and balance-alb modes, when | |
1737 | the active slave changes (e.g., due to a link failure), the | |
00354cfb | 1738 | promiscuous setting will be propagated to the new active slave. |
1da177e4 | 1739 | |
6224e01d | 1740 | 11. Configuring Bonding for High Availability |
00354cfb | 1741 | ============================================= |
1da177e4 LT |
1742 | |
1743 | High Availability refers to configurations that provide | |
1744 | maximum network availability by having redundant or backup devices, | |
00354cfb JV |
1745 | links or switches between the host and the rest of the world. The |
1746 | goal is to provide the maximum availability of network connectivity | |
1747 | (i.e., the network always works), even though other configurations | |
1748 | could provide higher throughput. | |
1da177e4 | 1749 | |
6224e01d | 1750 | 11.1 High Availability in a Single Switch Topology |
1da177e4 LT |
1751 | -------------------------------------------------- |
1752 | ||
00354cfb JV |
1753 | If two hosts (or a host and a single switch) are directly |
1754 | connected via multiple physical links, then there is no availability | |
1755 | penalty to optimizing for maximum bandwidth. In this case, there is | |
1756 | only one switch (or peer), so if it fails, there is no alternative | |
1757 | access to fail over to. Additionally, the bonding load balance modes | |
1758 | support link monitoring of their members, so if individual links fail, | |
1759 | the load will be rebalanced across the remaining devices. | |
1760 | ||
1761 | See Section 13, "Configuring Bonding for Maximum Throughput" | |
1762 | for information on configuring bonding with one peer device. | |
1763 | ||
6224e01d | 1764 | 11.2 High Availability in a Multiple Switch Topology |
00354cfb JV |
1765 | ---------------------------------------------------- |
1766 | ||
1767 | With multiple switches, the configuration of bonding and the | |
1768 | network changes dramatically. In multiple switch topologies, there is | |
1769 | a trade off between network availability and usable bandwidth. | |
1770 | ||
1771 | Below is a sample network, configured to maximize the | |
1772 | availability of the network: | |
1da177e4 | 1773 | |
00354cfb JV |
1774 | | | |
1775 | |port3 port3| | |
1776 | +-----+----+ +-----+----+ | |
1777 | | |port2 ISL port2| | | |
1778 | | switch A +--------------------------+ switch B | | |
1779 | | | | | | |
1780 | +-----+----+ +-----++---+ | |
1781 | |port1 port1| | |
1782 | | +-------+ | | |
1783 | +-------------+ host1 +---------------+ | |
1784 | eth0 +-------+ eth1 | |
1da177e4 | 1785 | |
00354cfb JV |
1786 | In this configuration, there is a link between the two |
1787 | switches (ISL, or inter switch link), and multiple ports connecting to | |
1788 | the outside world ("port3" on each switch). There is no technical | |
1789 | reason that this could not be extended to a third switch. | |
1da177e4 | 1790 | |
6224e01d | 1791 | 11.2.1 HA Bonding Mode Selection for Multiple Switch Topology |
00354cfb | 1792 | ------------------------------------------------------------- |
1da177e4 | 1793 | |
00354cfb JV |
1794 | In a topology such as the example above, the active-backup and |
1795 | broadcast modes are the only useful bonding modes when optimizing for | |
1796 | availability; the other modes require all links to terminate on the | |
1797 | same peer for them to behave rationally. | |
1798 | ||
1799 | active-backup: This is generally the preferred mode, particularly if | |
1800 | the switches have an ISL and play together well. If the | |
1801 | network configuration is such that one switch is specifically | |
1802 | a backup switch (e.g., has lower capacity, higher cost, etc), | |
1803 | then the primary option can be used to insure that the | |
1804 | preferred link is always used when it is available. | |
1805 | ||
1806 | broadcast: This mode is really a special purpose mode, and is suitable | |
1807 | only for very specific needs. For example, if the two | |
1808 | switches are not connected (no ISL), and the networks beyond | |
1809 | them are totally independent. In this case, if it is | |
1810 | necessary for some specific one-way traffic to reach both | |
1811 | independent networks, then the broadcast mode may be suitable. | |
1812 | ||
6224e01d | 1813 | 11.2.2 HA Link Monitoring Selection for Multiple Switch Topology |
00354cfb JV |
1814 | ---------------------------------------------------------------- |
1815 | ||
1816 | The choice of link monitoring ultimately depends upon your | |
1817 | switch. If the switch can reliably fail ports in response to other | |
1818 | failures, then either the MII or ARP monitors should work. For | |
1819 | example, in the above example, if the "port3" link fails at the remote | |
1820 | end, the MII monitor has no direct means to detect this. The ARP | |
1821 | monitor could be configured with a target at the remote end of port3, | |
1822 | thus detecting that failure without switch support. | |
1823 | ||
1824 | In general, however, in a multiple switch topology, the ARP | |
1825 | monitor can provide a higher level of reliability in detecting end to | |
1826 | end connectivity failures (which may be caused by the failure of any | |
1827 | individual component to pass traffic for any reason). Additionally, | |
1828 | the ARP monitor should be configured with multiple targets (at least | |
1829 | one for each switch in the network). This will insure that, | |
1830 | regardless of which switch is active, the ARP monitor has a suitable | |
1831 | target to query. | |
1832 | ||
9a6c6867 JV |
1833 | Note, also, that of late many switches now support a functionality |
1834 | generally referred to as "trunk failover." This is a feature of the | |
1835 | switch that causes the link state of a particular switch port to be set | |
1836 | down (or up) when the state of another switch port goes down (or up). | |
19f59460 | 1837 | Its purpose is to propagate link failures from logically "exterior" ports |
9a6c6867 JV |
1838 | to the logically "interior" ports that bonding is able to monitor via |
1839 | miimon. Availability and configuration for trunk failover varies by | |
1840 | switch, but this can be a viable alternative to the ARP monitor when using | |
1841 | suitable switches. | |
00354cfb | 1842 | |
6224e01d | 1843 | 12. Configuring Bonding for Maximum Throughput |
00354cfb JV |
1844 | ============================================== |
1845 | ||
6224e01d | 1846 | 12.1 Maximizing Throughput in a Single Switch Topology |
00354cfb JV |
1847 | ------------------------------------------------------ |
1848 | ||
1849 | In a single switch configuration, the best method to maximize | |
1850 | throughput depends upon the application and network environment. The | |
1851 | various load balancing modes each have strengths and weaknesses in | |
1852 | different environments, as detailed below. | |
1853 | ||
1854 | For this discussion, we will break down the topologies into | |
1855 | two categories. Depending upon the destination of most traffic, we | |
1856 | categorize them into either "gatewayed" or "local" configurations. | |
1857 | ||
1858 | In a gatewayed configuration, the "switch" is acting primarily | |
1859 | as a router, and the majority of traffic passes through this router to | |
1860 | other networks. An example would be the following: | |
1861 | ||
1862 | ||
1863 | +----------+ +----------+ | |
1864 | | |eth0 port1| | to other networks | |
1865 | | Host A +---------------------+ router +-------------------> | |
1866 | | +---------------------+ | Hosts B and C are out | |
1867 | | |eth1 port2| | here somewhere | |
1868 | +----------+ +----------+ | |
1869 | ||
1870 | The router may be a dedicated router device, or another host | |
1871 | acting as a gateway. For our discussion, the important point is that | |
1872 | the majority of traffic from Host A will pass through the router to | |
1873 | some other network before reaching its final destination. | |
1874 | ||
1875 | In a gatewayed network configuration, although Host A may | |
1876 | communicate with many other systems, all of its traffic will be sent | |
1877 | and received via one other peer on the local network, the router. | |
1878 | ||
1879 | Note that the case of two systems connected directly via | |
1880 | multiple physical links is, for purposes of configuring bonding, the | |
1881 | same as a gatewayed configuration. In that case, it happens that all | |
1882 | traffic is destined for the "gateway" itself, not some other network | |
1883 | beyond the gateway. | |
1884 | ||
1885 | In a local configuration, the "switch" is acting primarily as | |
1886 | a switch, and the majority of traffic passes through this switch to | |
1887 | reach other stations on the same network. An example would be the | |
1888 | following: | |
1889 | ||
1890 | +----------+ +----------+ +--------+ | |
1891 | | |eth0 port1| +-------+ Host B | | |
1892 | | Host A +------------+ switch |port3 +--------+ | |
1893 | | +------------+ | +--------+ | |
1894 | | |eth1 port2| +------------------+ Host C | | |
1895 | +----------+ +----------+port4 +--------+ | |
1896 | ||
1897 | ||
1898 | Again, the switch may be a dedicated switch device, or another | |
1899 | host acting as a gateway. For our discussion, the important point is | |
1900 | that the majority of traffic from Host A is destined for other hosts | |
1901 | on the same local network (Hosts B and C in the above example). | |
1902 | ||
1903 | In summary, in a gatewayed configuration, traffic to and from | |
1904 | the bonded device will be to the same MAC level peer on the network | |
1905 | (the gateway itself, i.e., the router), regardless of its final | |
1906 | destination. In a local configuration, traffic flows directly to and | |
1907 | from the final destinations, thus, each destination (Host B, Host C) | |
1908 | will be addressed directly by their individual MAC addresses. | |
1909 | ||
1910 | This distinction between a gatewayed and a local network | |
1911 | configuration is important because many of the load balancing modes | |
1912 | available use the MAC addresses of the local network source and | |
1913 | destination to make load balancing decisions. The behavior of each | |
1914 | mode is described below. | |
1915 | ||
1916 | ||
6224e01d | 1917 | 12.1.1 MT Bonding Mode Selection for Single Switch Topology |
00354cfb | 1918 | ----------------------------------------------------------- |
1da177e4 LT |
1919 | |
1920 | This configuration is the easiest to set up and to understand, | |
1921 | although you will have to decide which bonding mode best suits your | |
00354cfb | 1922 | needs. The trade offs for each mode are detailed below: |
1da177e4 LT |
1923 | |
1924 | balance-rr: This mode is the only mode that will permit a single | |
1925 | TCP/IP connection to stripe traffic across multiple | |
1926 | interfaces. It is therefore the only mode that will allow a | |
1927 | single TCP/IP stream to utilize more than one interface's | |
1928 | worth of throughput. This comes at a cost, however: the | |
9a6c6867 | 1929 | striping generally results in peer systems receiving packets out |
1da177e4 LT |
1930 | of order, causing TCP/IP's congestion control system to kick |
1931 | in, often by retransmitting segments. | |
1932 | ||
1933 | It is possible to adjust TCP/IP's congestion limits by | |
1934 | altering the net.ipv4.tcp_reordering sysctl parameter. The | |
1935 | usual default value is 3, and the maximum useful value is 127. | |
1936 | For a four interface balance-rr bond, expect that a single | |
1937 | TCP/IP stream will utilize no more than approximately 2.3 | |
1938 | interface's worth of throughput, even after adjusting | |
1939 | tcp_reordering. | |
1940 | ||
9a6c6867 JV |
1941 | Note that the fraction of packets that will be delivered out of |
1942 | order is highly variable, and is unlikely to be zero. The level | |
1943 | of reordering depends upon a variety of factors, including the | |
1944 | networking interfaces, the switch, and the topology of the | |
1945 | configuration. Speaking in general terms, higher speed network | |
1946 | cards produce more reordering (due to factors such as packet | |
1947 | coalescing), and a "many to many" topology will reorder at a | |
1948 | higher rate than a "many slow to one fast" configuration. | |
1949 | ||
1950 | Many switches do not support any modes that stripe traffic | |
1951 | (instead choosing a port based upon IP or MAC level addresses); | |
1952 | for those devices, traffic for a particular connection flowing | |
1953 | through the switch to a balance-rr bond will not utilize greater | |
1954 | than one interface's worth of bandwidth. | |
00354cfb | 1955 | |
1da177e4 LT |
1956 | If you are utilizing protocols other than TCP/IP, UDP for |
1957 | example, and your application can tolerate out of order | |
1958 | delivery, then this mode can allow for single stream datagram | |
1959 | performance that scales near linearly as interfaces are added | |
1960 | to the bond. | |
1961 | ||
1962 | This mode requires the switch to have the appropriate ports | |
1963 | configured for "etherchannel" or "trunking." | |
1964 | ||
1965 | active-backup: There is not much advantage in this network topology to | |
1966 | the active-backup mode, as the inactive backup devices are all | |
1967 | connected to the same peer as the primary. In this case, a | |
1968 | load balancing mode (with link monitoring) will provide the | |
1969 | same level of network availability, but with increased | |
00354cfb JV |
1970 | available bandwidth. On the plus side, active-backup mode |
1971 | does not require any configuration of the switch, so it may | |
1972 | have value if the hardware available does not support any of | |
1973 | the load balance modes. | |
1da177e4 LT |
1974 | |
1975 | balance-xor: This mode will limit traffic such that packets destined | |
1976 | for specific peers will always be sent over the same | |
1977 | interface. Since the destination is determined by the MAC | |
00354cfb JV |
1978 | addresses involved, this mode works best in a "local" network |
1979 | configuration (as described above), with destinations all on | |
1980 | the same local network. This mode is likely to be suboptimal | |
1981 | if all your traffic is passed through a single router (i.e., a | |
1982 | "gatewayed" network configuration, as described above). | |
1983 | ||
1984 | As with balance-rr, the switch ports need to be configured for | |
1da177e4 LT |
1985 | "etherchannel" or "trunking." |
1986 | ||
1987 | broadcast: Like active-backup, there is not much advantage to this | |
1988 | mode in this type of network topology. | |
1989 | ||
1990 | 802.3ad: This mode can be a good choice for this type of network | |
1991 | topology. The 802.3ad mode is an IEEE standard, so all peers | |
1992 | that implement 802.3ad should interoperate well. The 802.3ad | |
1993 | protocol includes automatic configuration of the aggregates, | |
1994 | so minimal manual configuration of the switch is needed | |
1995 | (typically only to designate that some set of devices is | |
00354cfb JV |
1996 | available for 802.3ad). The 802.3ad standard also mandates |
1997 | that frames be delivered in order (within certain limits), so | |
1998 | in general single connections will not see misordering of | |
1da177e4 LT |
1999 | packets. The 802.3ad mode does have some drawbacks: the |
2000 | standard mandates that all devices in the aggregate operate at | |
2001 | the same speed and duplex. Also, as with all bonding load | |
2002 | balance modes other than balance-rr, no single connection will | |
2003 | be able to utilize more than a single interface's worth of | |
00354cfb JV |
2004 | bandwidth. |
2005 | ||
2006 | Additionally, the linux bonding 802.3ad implementation | |
2007 | distributes traffic by peer (using an XOR of MAC addresses), | |
2008 | so in a "gatewayed" configuration, all outgoing traffic will | |
2009 | generally use the same device. Incoming traffic may also end | |
2010 | up on a single device, but that is dependent upon the | |
2011 | balancing policy of the peer's 8023.ad implementation. In a | |
2012 | "local" configuration, traffic will be distributed across the | |
2013 | devices in the bond. | |
2014 | ||
2015 | Finally, the 802.3ad mode mandates the use of the MII monitor, | |
2016 | therefore, the ARP monitor is not available in this mode. | |
2017 | ||
2018 | balance-tlb: The balance-tlb mode balances outgoing traffic by peer. | |
2019 | Since the balancing is done according to MAC address, in a | |
2020 | "gatewayed" configuration (as described above), this mode will | |
2021 | send all traffic across a single device. However, in a | |
2022 | "local" network configuration, this mode balances multiple | |
2023 | local network peers across devices in a vaguely intelligent | |
2024 | manner (not a simple XOR as in balance-xor or 802.3ad mode), | |
2025 | so that mathematically unlucky MAC addresses (i.e., ones that | |
2026 | XOR to the same value) will not all "bunch up" on a single | |
2027 | interface. | |
2028 | ||
2029 | Unlike 802.3ad, interfaces may be of differing speeds, and no | |
2030 | special switch configuration is required. On the down side, | |
2031 | in this mode all incoming traffic arrives over a single | |
2032 | interface, this mode requires certain ethtool support in the | |
2033 | network device driver of the slave interfaces, and the ARP | |
2034 | monitor is not available. | |
2035 | ||
2036 | balance-alb: This mode is everything that balance-tlb is, and more. | |
2037 | It has all of the features (and restrictions) of balance-tlb, | |
2038 | and will also balance incoming traffic from local network | |
2039 | peers (as described in the Bonding Module Options section, | |
2040 | above). | |
2041 | ||
2042 | The only additional down side to this mode is that the network | |
2043 | device driver must support changing the hardware address while | |
2044 | the device is open. | |
2045 | ||
6224e01d | 2046 | 12.1.2 MT Link Monitoring for Single Switch Topology |
00354cfb | 2047 | ---------------------------------------------------- |
1da177e4 LT |
2048 | |
2049 | The choice of link monitoring may largely depend upon which | |
2050 | mode you choose to use. The more advanced load balancing modes do not | |
2051 | support the use of the ARP monitor, and are thus restricted to using | |
00354cfb JV |
2052 | the MII monitor (which does not provide as high a level of end to end |
2053 | assurance as the ARP monitor). | |
2054 | ||
6224e01d | 2055 | 12.2 Maximum Throughput in a Multiple Switch Topology |
00354cfb JV |
2056 | ----------------------------------------------------- |
2057 | ||
2058 | Multiple switches may be utilized to optimize for throughput | |
2059 | when they are configured in parallel as part of an isolated network | |
2060 | between two or more systems, for example: | |
2061 | ||
2062 | +-----------+ | |
2063 | | Host A | | |
2064 | +-+---+---+-+ | |
2065 | | | | | |
2066 | +--------+ | +---------+ | |
2067 | | | | | |
2068 | +------+---+ +-----+----+ +-----+----+ | |
2069 | | Switch A | | Switch B | | Switch C | | |
2070 | +------+---+ +-----+----+ +-----+----+ | |
2071 | | | | | |
2072 | +--------+ | +---------+ | |
2073 | | | | | |
2074 | +-+---+---+-+ | |
2075 | | Host B | | |
2076 | +-----------+ | |
2077 | ||
2078 | In this configuration, the switches are isolated from one | |
2079 | another. One reason to employ a topology such as this is for an | |
2080 | isolated network with many hosts (a cluster configured for high | |
2081 | performance, for example), using multiple smaller switches can be more | |
2082 | cost effective than a single larger switch, e.g., on a network with 24 | |
2083 | hosts, three 24 port switches can be significantly less expensive than | |
2084 | a single 72 port switch. | |
2085 | ||
2086 | If access beyond the network is required, an individual host | |
2087 | can be equipped with an additional network device connected to an | |
2088 | external network; this host then additionally acts as a gateway. | |
2089 | ||
6224e01d | 2090 | 12.2.1 MT Bonding Mode Selection for Multiple Switch Topology |
1da177e4 LT |
2091 | ------------------------------------------------------------- |
2092 | ||
00354cfb JV |
2093 | In actual practice, the bonding mode typically employed in |
2094 | configurations of this type is balance-rr. Historically, in this | |
2095 | network configuration, the usual caveats about out of order packet | |
2096 | delivery are mitigated by the use of network adapters that do not do | |
2097 | any kind of packet coalescing (via the use of NAPI, or because the | |
2098 | device itself does not generate interrupts until some number of | |
2099 | packets has arrived). When employed in this fashion, the balance-rr | |
2100 | mode allows individual connections between two hosts to effectively | |
2101 | utilize greater than one interface's bandwidth. | |
1da177e4 | 2102 | |
6224e01d | 2103 | 12.2.2 MT Link Monitoring for Multiple Switch Topology |
00354cfb | 2104 | ------------------------------------------------------ |
1da177e4 | 2105 | |
00354cfb JV |
2106 | Again, in actual practice, the MII monitor is most often used |
2107 | in this configuration, as performance is given preference over | |
2108 | availability. The ARP monitor will function in this topology, but its | |
2109 | advantages over the MII monitor are mitigated by the volume of probes | |
2110 | needed as the number of systems involved grows (remember that each | |
2111 | host in the network is configured with bonding). | |
1da177e4 | 2112 | |
6224e01d | 2113 | 13. Switch Behavior Issues |
00354cfb | 2114 | ========================== |
1da177e4 | 2115 | |
6224e01d | 2116 | 13.1 Link Establishment and Failover Delays |
00354cfb JV |
2117 | ------------------------------------------- |
2118 | ||
2119 | Some switches exhibit undesirable behavior with regard to the | |
2120 | timing of link up and down reporting by the switch. | |
1da177e4 LT |
2121 | |
2122 | First, when a link comes up, some switches may indicate that | |
2123 | the link is up (carrier available), but not pass traffic over the | |
2124 | interface for some period of time. This delay is typically due to | |
2125 | some type of autonegotiation or routing protocol, but may also occur | |
2126 | during switch initialization (e.g., during recovery after a switch | |
2127 | failure). If you find this to be a problem, specify an appropriate | |
2128 | value to the updelay bonding module option to delay the use of the | |
2129 | relevant interface(s). | |
2130 | ||
2131 | Second, some switches may "bounce" the link state one or more | |
2132 | times while a link is changing state. This occurs most commonly while | |
2133 | the switch is initializing. Again, an appropriate updelay value may | |
00354cfb | 2134 | help. |
1da177e4 LT |
2135 | |
2136 | Note that when a bonding interface has no active links, the | |
00354cfb JV |
2137 | driver will immediately reuse the first link that goes up, even if the |
2138 | updelay parameter has been specified (the updelay is ignored in this | |
2139 | case). If there are slave interfaces waiting for the updelay timeout | |
2140 | to expire, the interface that first went into that state will be | |
2141 | immediately reused. This reduces down time of the network if the | |
2142 | value of updelay has been overestimated, and since this occurs only in | |
2143 | cases with no connectivity, there is no additional penalty for | |
2144 | ignoring the updelay. | |
1da177e4 LT |
2145 | |
2146 | In addition to the concerns about switch timings, if your | |
2147 | switches take a long time to go into backup mode, it may be desirable | |
2148 | to not activate a backup interface immediately after a link goes down. | |
2149 | Failover may be delayed via the downdelay bonding module option. | |
2150 | ||
6224e01d | 2151 | 13.2 Duplicated Incoming Packets |
00354cfb JV |
2152 | -------------------------------- |
2153 | ||
9a6c6867 JV |
2154 | NOTE: Starting with version 3.0.2, the bonding driver has logic to |
2155 | suppress duplicate packets, which should largely eliminate this problem. | |
2156 | The following description is kept for reference. | |
2157 | ||
00354cfb JV |
2158 | It is not uncommon to observe a short burst of duplicated |
2159 | traffic when the bonding device is first used, or after it has been | |
2160 | idle for some period of time. This is most easily observed by issuing | |
2161 | a "ping" to some other host on the network, and noticing that the | |
2162 | output from ping flags duplicates (typically one per slave). | |
2163 | ||
2164 | For example, on a bond in active-backup mode with five slaves | |
2165 | all connected to one switch, the output may appear as follows: | |
2166 | ||
2167 | # ping -n 10.0.4.2 | |
2168 | PING 10.0.4.2 (10.0.4.2) from 10.0.3.10 : 56(84) bytes of data. | |
2169 | 64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.7 ms | |
2170 | 64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!) | |
2171 | 64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!) | |
2172 | 64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!) | |
2173 | 64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!) | |
2174 | 64 bytes from 10.0.4.2: icmp_seq=2 ttl=64 time=0.216 ms | |
2175 | 64 bytes from 10.0.4.2: icmp_seq=3 ttl=64 time=0.267 ms | |
2176 | 64 bytes from 10.0.4.2: icmp_seq=4 ttl=64 time=0.222 ms | |
2177 | ||
2178 | This is not due to an error in the bonding driver, rather, it | |
2179 | is a side effect of how many switches update their MAC forwarding | |
2180 | tables. Initially, the switch does not associate the MAC address in | |
2181 | the packet with a particular switch port, and so it may send the | |
2182 | traffic to all ports until its MAC forwarding table is updated. Since | |
2183 | the interfaces attached to the bond may occupy multiple ports on a | |
2184 | single switch, when the switch (temporarily) floods the traffic to all | |
2185 | ports, the bond device receives multiple copies of the same packet | |
2186 | (one per slave device). | |
2187 | ||
2188 | The duplicated packet behavior is switch dependent, some | |
2189 | switches exhibit this, and some do not. On switches that display this | |
2190 | behavior, it can be induced by clearing the MAC forwarding table (on | |
2191 | most Cisco switches, the privileged command "clear mac address-table | |
2192 | dynamic" will accomplish this). | |
2193 | ||
6224e01d | 2194 | 14. Hardware Specific Considerations |
1da177e4 LT |
2195 | ==================================== |
2196 | ||
2197 | This section contains additional information for configuring | |
2198 | bonding on specific hardware platforms, or for interfacing bonding | |
2199 | with particular switches or other devices. | |
2200 | ||
6224e01d | 2201 | 14.1 IBM BladeCenter |
1da177e4 LT |
2202 | -------------------- |
2203 | ||
2204 | This applies to the JS20 and similar systems. | |
2205 | ||
2206 | On the JS20 blades, the bonding driver supports only | |
2207 | balance-rr, active-backup, balance-tlb and balance-alb modes. This is | |
2208 | largely due to the network topology inside the BladeCenter, detailed | |
2209 | below. | |
2210 | ||
2211 | JS20 network adapter information | |
2212 | -------------------------------- | |
2213 | ||
2214 | All JS20s come with two Broadcom Gigabit Ethernet ports | |
00354cfb JV |
2215 | integrated on the planar (that's "motherboard" in IBM-speak). In the |
2216 | BladeCenter chassis, the eth0 port of all JS20 blades is hard wired to | |
2217 | I/O Module #1; similarly, all eth1 ports are wired to I/O Module #2. | |
2218 | An add-on Broadcom daughter card can be installed on a JS20 to provide | |
2219 | two more Gigabit Ethernet ports. These ports, eth2 and eth3, are | |
2220 | wired to I/O Modules 3 and 4, respectively. | |
1da177e4 LT |
2221 | |
2222 | Each I/O Module may contain either a switch or a passthrough | |
2223 | module (which allows ports to be directly connected to an external | |
2224 | switch). Some bonding modes require a specific BladeCenter internal | |
2225 | network topology in order to function; these are detailed below. | |
2226 | ||
2227 | Additional BladeCenter-specific networking information can be | |
2228 | found in two IBM Redbooks (www.ibm.com/redbooks): | |
2229 | ||
2230 | "IBM eServer BladeCenter Networking Options" | |
2231 | "IBM eServer BladeCenter Layer 2-7 Network Switching" | |
2232 | ||
2233 | BladeCenter networking configuration | |
2234 | ------------------------------------ | |
2235 | ||
2236 | Because a BladeCenter can be configured in a very large number | |
2237 | of ways, this discussion will be confined to describing basic | |
2238 | configurations. | |
2239 | ||
00354cfb | 2240 | Normally, Ethernet Switch Modules (ESMs) are used in I/O |
1da177e4 LT |
2241 | modules 1 and 2. In this configuration, the eth0 and eth1 ports of a |
2242 | JS20 will be connected to different internal switches (in the | |
2243 | respective I/O modules). | |
2244 | ||
00354cfb JV |
2245 | A passthrough module (OPM or CPM, optical or copper, |
2246 | passthrough module) connects the I/O module directly to an external | |
2247 | switch. By using PMs in I/O module #1 and #2, the eth0 and eth1 | |
2248 | interfaces of a JS20 can be redirected to the outside world and | |
2249 | connected to a common external switch. | |
2250 | ||
2251 | Depending upon the mix of ESMs and PMs, the network will | |
2252 | appear to bonding as either a single switch topology (all PMs) or as a | |
2253 | multiple switch topology (one or more ESMs, zero or more PMs). It is | |
2254 | also possible to connect ESMs together, resulting in a configuration | |
2255 | much like the example in "High Availability in a Multiple Switch | |
2256 | Topology," above. | |
2257 | ||
2258 | Requirements for specific modes | |
2259 | ------------------------------- | |
2260 | ||
2261 | The balance-rr mode requires the use of passthrough modules | |
2262 | for devices in the bond, all connected to an common external switch. | |
2263 | That switch must be configured for "etherchannel" or "trunking" on the | |
1da177e4 LT |
2264 | appropriate ports, as is usual for balance-rr. |
2265 | ||
2266 | The balance-alb and balance-tlb modes will function with | |
2267 | either switch modules or passthrough modules (or a mix). The only | |
2268 | specific requirement for these modes is that all network interfaces | |
2269 | must be able to reach all destinations for traffic sent over the | |
2270 | bonding device (i.e., the network must converge at some point outside | |
2271 | the BladeCenter). | |
2272 | ||
2273 | The active-backup mode has no additional requirements. | |
2274 | ||
2275 | Link monitoring issues | |
2276 | ---------------------- | |
2277 | ||
2278 | When an Ethernet Switch Module is in place, only the ARP | |
2279 | monitor will reliably detect link loss to an external switch. This is | |
2280 | nothing unusual, but examination of the BladeCenter cabinet would | |
2281 | suggest that the "external" network ports are the ethernet ports for | |
2282 | the system, when it fact there is a switch between these "external" | |
2283 | ports and the devices on the JS20 system itself. The MII monitor is | |
2284 | only able to detect link failures between the ESM and the JS20 system. | |
2285 | ||
2286 | When a passthrough module is in place, the MII monitor does | |
2287 | detect failures to the "external" port, which is then directly | |
2288 | connected to the JS20 system. | |
2289 | ||
2290 | Other concerns | |
2291 | -------------- | |
2292 | ||
00354cfb | 2293 | The Serial Over LAN (SoL) link is established over the primary |
1da177e4 LT |
2294 | ethernet (eth0) only, therefore, any loss of link to eth0 will result |
2295 | in losing your SoL connection. It will not fail over with other | |
00354cfb JV |
2296 | network traffic, as the SoL system is beyond the control of the |
2297 | bonding driver. | |
1da177e4 LT |
2298 | |
2299 | It may be desirable to disable spanning tree on the switch | |
2300 | (either the internal Ethernet Switch Module, or an external switch) to | |
00354cfb | 2301 | avoid fail-over delay issues when using bonding. |
1da177e4 LT |
2302 | |
2303 | ||
6224e01d | 2304 | 15. Frequently Asked Questions |
1da177e4 LT |
2305 | ============================== |
2306 | ||
2307 | 1. Is it SMP safe? | |
2308 | ||
2309 | Yes. The old 2.0.xx channel bonding patch was not SMP safe. | |
2310 | The new driver was designed to be SMP safe from the start. | |
2311 | ||
2312 | 2. What type of cards will work with it? | |
2313 | ||
2314 | Any Ethernet type cards (you can even mix cards - a Intel | |
00354cfb JV |
2315 | EtherExpress PRO/100 and a 3com 3c905b, for example). For most modes, |
2316 | devices need not be of the same speed. | |
1da177e4 | 2317 | |
9a6c6867 JV |
2318 | Starting with version 3.2.1, bonding also supports Infiniband |
2319 | slaves in active-backup mode. | |
2320 | ||
1da177e4 LT |
2321 | 3. How many bonding devices can I have? |
2322 | ||
2323 | There is no limit. | |
2324 | ||
2325 | 4. How many slaves can a bonding device have? | |
2326 | ||
2327 | This is limited only by the number of network interfaces Linux | |
2328 | supports and/or the number of network cards you can place in your | |
2329 | system. | |
2330 | ||
2331 | 5. What happens when a slave link dies? | |
2332 | ||
2333 | If link monitoring is enabled, then the failing device will be | |
2334 | disabled. The active-backup mode will fail over to a backup link, and | |
2335 | other modes will ignore the failed link. The link will continue to be | |
2336 | monitored, and should it recover, it will rejoin the bond (in whatever | |
00354cfb JV |
2337 | manner is appropriate for the mode). See the sections on High |
2338 | Availability and the documentation for each mode for additional | |
2339 | information. | |
1da177e4 LT |
2340 | |
2341 | Link monitoring can be enabled via either the miimon or | |
00354cfb | 2342 | arp_interval parameters (described in the module parameters section, |
1da177e4 LT |
2343 | above). In general, miimon monitors the carrier state as sensed by |
2344 | the underlying network device, and the arp monitor (arp_interval) | |
2345 | monitors connectivity to another host on the local network. | |
2346 | ||
2347 | If no link monitoring is configured, the bonding driver will | |
2348 | be unable to detect link failures, and will assume that all links are | |
2349 | always available. This will likely result in lost packets, and a | |
00354cfb | 2350 | resulting degradation of performance. The precise performance loss |
1da177e4 LT |
2351 | depends upon the bonding mode and network configuration. |
2352 | ||
2353 | 6. Can bonding be used for High Availability? | |
2354 | ||
2355 | Yes. See the section on High Availability for details. | |
2356 | ||
2357 | 7. Which switches/systems does it work with? | |
2358 | ||
2359 | The full answer to this depends upon the desired mode. | |
2360 | ||
2361 | In the basic balance modes (balance-rr and balance-xor), it | |
2362 | works with any system that supports etherchannel (also called | |
2363 | trunking). Most managed switches currently available have such | |
00354cfb | 2364 | support, and many unmanaged switches as well. |
1da177e4 LT |
2365 | |
2366 | The advanced balance modes (balance-tlb and balance-alb) do | |
2367 | not have special switch requirements, but do need device drivers that | |
2368 | support specific features (described in the appropriate section under | |
00354cfb | 2369 | module parameters, above). |
1da177e4 | 2370 | |
6224e01d | 2371 | In 802.3ad mode, it works with systems that support IEEE |
1da177e4 LT |
2372 | 802.3ad Dynamic Link Aggregation. Most managed and many unmanaged |
2373 | switches currently available support 802.3ad. | |
2374 | ||
2375 | The active-backup mode should work with any Layer-II switch. | |
2376 | ||
2377 | 8. Where does a bonding device get its MAC address from? | |
2378 | ||
9a6c6867 JV |
2379 | When using slave devices that have fixed MAC addresses, or when |
2380 | the fail_over_mac option is enabled, the bonding device's MAC address is | |
2381 | the MAC address of the active slave. | |
2382 | ||
2383 | For other configurations, if not explicitly configured (with | |
2384 | ifconfig or ip link), the MAC address of the bonding device is taken from | |
2385 | its first slave device. This MAC address is then passed to all following | |
2386 | slaves and remains persistent (even if the first slave is removed) until | |
2387 | the bonding device is brought down or reconfigured. | |
1da177e4 LT |
2388 | |
2389 | If you wish to change the MAC address, you can set it with | |
00354cfb | 2390 | ifconfig or ip link: |
1da177e4 LT |
2391 | |
2392 | # ifconfig bond0 hw ether 00:11:22:33:44:55 | |
2393 | ||
00354cfb JV |
2394 | # ip link set bond0 address 66:77:88:99:aa:bb |
2395 | ||
1da177e4 LT |
2396 | The MAC address can be also changed by bringing down/up the |
2397 | device and then changing its slaves (or their order): | |
2398 | ||
2399 | # ifconfig bond0 down ; modprobe -r bonding | |
2400 | # ifconfig bond0 .... up | |
2401 | # ifenslave bond0 eth... | |
2402 | ||
2403 | This method will automatically take the address from the next | |
2404 | slave that is added. | |
2405 | ||
2406 | To restore your slaves' MAC addresses, you need to detach them | |
2407 | from the bond (`ifenslave -d bond0 eth0'). The bonding driver will | |
2408 | then restore the MAC addresses that the slaves had before they were | |
2409 | enslaved. | |
2410 | ||
00354cfb | 2411 | 16. Resources and Links |
1da177e4 LT |
2412 | ======================= |
2413 | ||
2414 | The latest version of the bonding driver can be found in the latest | |
2415 | version of the linux kernel, found on http://kernel.org | |
2416 | ||
00354cfb JV |
2417 | The latest version of this document can be found in either the latest |
2418 | kernel source (named Documentation/networking/bonding.txt), or on the | |
2419 | bonding sourceforge site: | |
2420 | ||
2421 | http://www.sourceforge.net/projects/bonding | |
2422 | ||
1da177e4 LT |
2423 | Discussions regarding the bonding driver take place primarily on the |
2424 | bonding-devel mailing list, hosted at sourceforge.net. If you have | |
00354cfb | 2425 | questions or problems, post them to the list. The list address is: |
1da177e4 LT |
2426 | |
2427 | bonding-devel@lists.sourceforge.net | |
2428 | ||
00354cfb JV |
2429 | The administrative interface (to subscribe or unsubscribe) can |
2430 | be found at: | |
1da177e4 | 2431 | |
00354cfb | 2432 | https://lists.sourceforge.net/lists/listinfo/bonding-devel |
1da177e4 LT |
2433 | |
2434 | Donald Becker's Ethernet Drivers and diag programs may be found at : | |
2435 | - http://www.scyld.com/network/ | |
2436 | ||
2437 | You will also find a lot of information regarding Ethernet, NWay, MII, | |
2438 | etc. at www.scyld.com. | |
2439 | ||
2440 | -- END -- |