1 .. SPDX-License-Identifier: GPL-2.0
3 ===================================
4 Linux Ethernet Bonding Driver HOWTO
5 ===================================
7 Latest update: 27 April 2011
9 Initial release: Thomas Davis <tadavis at lbl.gov>
11 Corrections, HA extensions: 2000/10/03-15:
13 - Willy Tarreau <willy at meta-x.org>
14 - Constantine Gavrilov <const-g at xpert.com>
15 - Chad N. Tindel <ctindel at ieee dot org>
16 - Janice Girouard <girouard at us dot ibm dot com>
17 - Jay Vosburgh <fubar at us dot ibm dot com>
19 Reorganized and updated Feb 2005 by Jay Vosburgh
20 Added Sysfs information: 2006/04/24
22 - Mitch Williams <mitch.a.williams at intel.com>
27 The Linux bonding driver provides a method for aggregating
28 multiple network interfaces into a single logical "bonded" interface.
29 The behavior of the bonded interfaces depends upon the mode; generally
30 speaking, modes provide either hot standby or load balancing services.
31 Additionally, link integrity monitoring may be performed.
33 The bonding driver originally came from Donald Becker's
34 beowulf patches for kernel 2.0. It has changed quite a bit since, and
35 the original tools from extreme-linux and beowulf sites will not work
36 with this version of the driver.
38 For new versions of the driver, updated userspace tools, and
39 who to ask for help, please follow the links at the end of this file.
43 1. Bonding Driver Installation
45 2. Bonding Driver Options
47 3. Configuring Bonding Devices
48 3.1 Configuration with Sysconfig Support
49 3.1.1 Using DHCP with Sysconfig
50 3.1.2 Configuring Multiple Bonds with Sysconfig
51 3.2 Configuration with Initscripts Support
52 3.2.1 Using DHCP with Initscripts
53 3.2.2 Configuring Multiple Bonds with Initscripts
54 3.3 Configuring Bonding Manually with Ifenslave
55 3.3.1 Configuring Multiple Bonds Manually
56 3.4 Configuring Bonding Manually via Sysfs
57 3.5 Configuration with Interfaces Support
58 3.6 Overriding Configuration for Special Cases
59 3.7 Configuring LACP for 802.3ad mode in a more secure way
61 4. Querying Bonding Configuration
62 4.1 Bonding Configuration
63 4.2 Network Configuration
65 5. Switch Configuration
67 6. 802.1q VLAN Support
70 7.1 ARP Monitor Operation
71 7.2 Configuring Multiple ARP Targets
72 7.3 MII Monitor Operation
74 8. Potential Trouble Sources
75 8.1 Adventures in Routing
76 8.2 Ethernet Device Renaming
77 8.3 Painfully Slow Or No Failed Link Detection By Miimon
83 11. Configuring Bonding for High Availability
84 11.1 High Availability in a Single Switch Topology
85 11.2 High Availability in a Multiple Switch Topology
86 11.2.1 HA Bonding Mode Selection for Multiple Switch Topology
87 11.2.2 HA Link Monitoring for Multiple Switch Topology
89 12. Configuring Bonding for Maximum Throughput
90 12.1 Maximum Throughput in a Single Switch Topology
91 12.1.1 MT Bonding Mode Selection for Single Switch Topology
92 12.1.2 MT Link Monitoring for Single Switch Topology
93 12.2 Maximum Throughput in a Multiple Switch Topology
94 12.2.1 MT Bonding Mode Selection for Multiple Switch Topology
95 12.2.2 MT Link Monitoring for Multiple Switch Topology
97 13. Switch Behavior Issues
98 13.1 Link Establishment and Failover Delays
99 13.2 Duplicated Incoming Packets
101 14. Hardware Specific Considerations
104 15. Frequently Asked Questions
106 16. Resources and Links
109 1. Bonding Driver Installation
110 ==============================
112 Most popular distro kernels ship with the bonding driver
113 already available as a module. If your distro does not, or you
114 have need to compile bonding from source (e.g., configuring and
115 installing a mainline kernel from kernel.org), you'll need to perform
118 1.1 Configure and build the kernel with bonding
119 -----------------------------------------------
121 The current version of the bonding driver is available in the
122 drivers/net/bonding subdirectory of the most recent kernel source
123 (which is available on http://kernel.org). Most users "rolling their
124 own" will want to use the most recent kernel from kernel.org.
126 Configure kernel with "make menuconfig" (or "make xconfig" or
127 "make config"), then select "Bonding driver support" in the "Network
128 device support" section. It is recommended that you configure the
129 driver as module since it is currently the only way to pass parameters
130 to the driver or configure more than one bonding device.
132 Build and install the new kernel and modules.
134 1.2 Bonding Control Utility
135 ---------------------------
137 It is recommended to configure bonding via iproute2 (netlink)
138 or sysfs, the old ifenslave control utility is obsolete.
140 2. Bonding Driver Options
141 =========================
143 Options for the bonding driver are supplied as parameters to the
144 bonding module at load time, or are specified via sysfs.
146 Module options may be given as command line arguments to the
147 insmod or modprobe command, but are usually specified in either the
148 ``/etc/modprobe.d/*.conf`` configuration files, or in a distro-specific
149 configuration file (some of which are detailed in the next section).
151 Details on bonding support for sysfs is provided in the
152 "Configuring Bonding Manually via Sysfs" section, below.
154 The available bonding driver parameters are listed below. If a
155 parameter is not specified the default value is used. When initially
156 configuring a bond, it is recommended "tail -f /var/log/messages" be
157 run in a separate window to watch for bonding driver error messages.
159 It is critical that either the miimon or arp_interval and
160 arp_ip_target parameters be specified, otherwise serious network
161 degradation will occur during link failures. Very few devices do not
162 support at least miimon, so there is really no reason not to use it.
164 Options with textual values will accept either the text name
165 or, for backwards compatibility, the option value. E.g.,
166 "mode=802.3ad" and "mode=4" set the same mode.
168 The parameters are as follows:
172 Specifies the new active slave for modes that support it
173 (active-backup, balance-alb and balance-tlb). Possible values
174 are the name of any currently enslaved interface, or an empty
175 string. If a name is given, the slave and its link must be up in order
176 to be selected as the new active slave. If an empty string is
177 specified, the current active slave is cleared, and a new active
178 slave is selected automatically.
180 Note that this is only available through the sysfs interface. No module
181 parameter by this name exists.
183 The normal value of this option is the name of the currently
184 active slave, or the empty string if there is no active slave or
185 the current mode does not use an active slave.
189 In an AD system, this specifies the system priority. The allowed range
190 is 1 - 65535. If the value is not specified, it takes 65535 as the
193 This parameter has effect only in 802.3ad mode and is available through
198 In an AD system, this specifies the mac-address for the actor in
199 protocol packet exchanges (LACPDUs). The value cannot be a multicast
200 address. If the all-zeroes MAC is specified, bonding will internally
201 use the MAC of the bond itself. It is preferred to have the
202 local-admin bit set for this mac but driver does not enforce it. If
203 the value is not given then system defaults to using the masters'
204 mac address as actors' system address.
206 This parameter has effect only in 802.3ad mode and is available through
211 Specifies the 802.3ad aggregation selection logic to use. The
212 possible values and their effects are:
216 The active aggregator is chosen by largest aggregate
219 Reselection of the active aggregator occurs only when all
220 slaves of the active aggregator are down or the active
221 aggregator has no slaves.
223 This is the default value.
227 The active aggregator is chosen by largest aggregate
228 bandwidth. Reselection occurs if:
230 - A slave is added to or removed from the bond
232 - Any slave's link state changes
234 - Any slave's 802.3ad association state changes
236 - The bond's administrative state changes to up
240 The active aggregator is chosen by the largest number of
241 ports (slaves). Reselection occurs as described under the
242 "bandwidth" setting, above.
244 The bandwidth and count selection policies permit failover of
245 802.3ad aggregations when partial failure of the active aggregator
246 occurs. This keeps the aggregator with the highest availability
247 (either in bandwidth or in number of ports) active at all times.
249 This option was added in bonding version 3.4.0.
253 In an AD system, the port-key has three parts as shown below -
263 This defines the upper 10 bits of the port key. The values can be
264 from 0 - 1023. If not given, the system defaults to 0.
266 This parameter has effect only in 802.3ad mode and is available through
271 Specifies that duplicate frames (received on inactive ports) should be
272 dropped (0) or delivered (1).
274 Normally, bonding will drop duplicate frames (received on inactive
275 ports), which is desirable for most users. But there are some times
276 it is nice to allow duplicate frames to be delivered.
278 The default value is 0 (drop duplicate frames received on inactive
283 Specifies the ARP link monitoring frequency in milliseconds.
285 The ARP monitor works by periodically checking the slave
286 devices to determine whether they have sent or received
287 traffic recently (the precise criteria depends upon the
288 bonding mode, and the state of the slave). Regular traffic is
289 generated via ARP probes issued for the addresses specified by
290 the arp_ip_target option.
292 This behavior can be modified by the arp_validate option,
295 If ARP monitoring is used in an etherchannel compatible mode
296 (modes 0 and 2), the switch should be configured in a mode
297 that evenly distributes packets across all links. If the
298 switch is configured to distribute the packets in an XOR
299 fashion, all replies from the ARP targets will be received on
300 the same link which could cause the other team members to
301 fail. ARP monitoring should not be used in conjunction with
302 miimon. A value of 0 disables ARP monitoring. The default
307 Specifies the IP addresses to use as ARP monitoring peers when
308 arp_interval is > 0. These are the targets of the ARP request
309 sent to determine the health of the link to the targets.
310 Specify these values in ddd.ddd.ddd.ddd format. Multiple IP
311 addresses must be separated by a comma. At least one IP
312 address must be given for ARP monitoring to function. The
313 maximum number of targets that can be specified is 16. The
314 default value is no IP addresses.
318 Specifies the IPv6 addresses to use as IPv6 monitoring peers when
319 arp_interval is > 0. These are the targets of the NS request
320 sent to determine the health of the link to the targets.
321 Specify these values in ffff:ffff::ffff:ffff format. Multiple IPv6
322 addresses must be separated by a comma. At least one IPv6
323 address must be given for NS/NA monitoring to function. The
324 maximum number of targets that can be specified is 16. The
325 default value is no IPv6 addresses.
329 Specifies whether or not ARP probes and replies should be
330 validated in any mode that supports arp monitoring, or whether
331 non-ARP traffic should be filtered (disregarded) for link
338 No validation or filtering is performed.
342 Validation is performed only for the active slave.
346 Validation is performed only for backup slaves.
350 Validation is performed for all slaves.
354 Filtering is applied to all slaves. No validation is
359 Filtering is applied to all slaves, validation is performed
360 only for the active slave.
364 Filtering is applied to all slaves, validation is performed
365 only for backup slaves.
369 Enabling validation causes the ARP monitor to examine the incoming
370 ARP requests and replies, and only consider a slave to be up if it
371 is receiving the appropriate ARP traffic.
373 For an active slave, the validation checks ARP replies to confirm
374 that they were generated by an arp_ip_target. Since backup slaves
375 do not typically receive these replies, the validation performed
376 for backup slaves is on the broadcast ARP request sent out via the
377 active slave. It is possible that some switch or network
378 configurations may result in situations wherein the backup slaves
379 do not receive the ARP requests; in such a situation, validation
380 of backup slaves must be disabled.
382 The validation of ARP requests on backup slaves is mainly helping
383 bonding to decide which slaves are more likely to work in case of
384 the active slave failure, it doesn't really guarantee that the
385 backup slave will work if it's selected as the next active slave.
387 Validation is useful in network configurations in which multiple
388 bonding hosts are concurrently issuing ARPs to one or more targets
389 beyond a common switch. Should the link between the switch and
390 target fail (but not the switch itself), the probe traffic
391 generated by the multiple bonding instances will fool the standard
392 ARP monitor into considering the links as still up. Use of
393 validation can resolve this, as the ARP monitor will only consider
394 ARP requests and replies associated with its own instance of
399 Enabling filtering causes the ARP monitor to only use incoming ARP
400 packets for link availability purposes. Arriving packets that are
401 not ARPs are delivered normally, but do not count when determining
402 if a slave is available.
404 Filtering operates by only considering the reception of ARP
405 packets (any ARP packet, regardless of source or destination) when
406 determining if a slave has received traffic for link availability
409 Filtering is useful in network configurations in which significant
410 levels of third party broadcast traffic would fool the standard
411 ARP monitor into considering the links as still up. Use of
412 filtering can resolve this, as only ARP traffic is considered for
413 link availability purposes.
415 This option was added in bonding version 3.1.0.
419 Specifies the quantity of arp_ip_targets that must be reachable
420 in order for the ARP monitor to consider a slave as being up.
421 This option affects only active-backup mode for slaves with
422 arp_validation enabled.
428 consider the slave up only when any of the arp_ip_targets
433 consider the slave up only when all of the arp_ip_targets
438 Specifies the number of arp_interval monitor checks that must
439 fail in order for an interface to be marked down by the ARP monitor.
441 In order to provide orderly failover semantics, backup interfaces
442 are permitted an extra monitor check (i.e., they must fail
443 arp_missed_max + 1 times before being marked down).
445 The default value is 2, and the allowable range is 1 - 255.
449 Specifies the time, in milliseconds, to wait before disabling
450 a slave after a link failure has been detected. This option
451 is only valid for the miimon link monitor. The downdelay
452 value should be a multiple of the miimon value; if not, it
453 will be rounded down to the nearest multiple. The default
458 Specifies whether active-backup mode should set all slaves to
459 the same MAC address at enslavement (the traditional
460 behavior), or, when enabled, perform special handling of the
461 bond's MAC address in accordance with the selected policy.
467 This setting disables fail_over_mac, and causes
468 bonding to set all slaves of an active-backup bond to
469 the same MAC address at enslavement time. This is the
474 The "active" fail_over_mac policy indicates that the
475 MAC address of the bond should always be the MAC
476 address of the currently active slave. The MAC
477 address of the slaves is not changed; instead, the MAC
478 address of the bond changes during a failover.
480 This policy is useful for devices that cannot ever
481 alter their MAC address, or for devices that refuse
482 incoming broadcasts with their own source MAC (which
483 interferes with the ARP monitor).
485 The down side of this policy is that every device on
486 the network must be updated via gratuitous ARP,
487 vs. just updating a switch or set of switches (which
488 often takes place for any traffic, not just ARP
489 traffic, if the switch snoops incoming traffic to
490 update its tables) for the traditional method. If the
491 gratuitous ARP is lost, communication may be
494 When this policy is used in conjunction with the mii
495 monitor, devices which assert link up prior to being
496 able to actually transmit and receive are particularly
497 susceptible to loss of the gratuitous ARP, and an
498 appropriate updelay setting may be required.
502 The "follow" fail_over_mac policy causes the MAC
503 address of the bond to be selected normally (normally
504 the MAC address of the first slave added to the bond).
505 However, the second and subsequent slaves are not set
506 to this MAC address while they are in a backup role; a
507 slave is programmed with the bond's MAC address at
508 failover time (and the formerly active slave receives
509 the newly active slave's MAC address).
511 This policy is useful for multiport devices that
512 either become confused or incur a performance penalty
513 when multiple ports are programmed with the same MAC
517 The default policy is none, unless the first slave cannot
518 change its MAC address, in which case the active policy is
521 This option may be modified via sysfs only when no slaves are
524 This option was added in bonding version 3.2.0. The "follow"
525 policy was added in bonding version 3.3.0.
528 Option specifying whether to send LACPDU frames periodically.
531 LACPDU frames acts as "speak when spoken to".
534 LACPDU frames are sent along the configured links
535 periodically. See lacp_rate for more details.
541 Option specifying the rate in which we'll ask our link partner
542 to transmit LACPDU packets in 802.3ad mode. Possible values
546 Request partner to transmit LACPDUs every 30 seconds
549 Request partner to transmit LACPDUs every 1 second
555 Specifies the number of bonding devices to create for this
556 instance of the bonding driver. E.g., if max_bonds is 3, and
557 the bonding driver is not already loaded, then bond0, bond1
558 and bond2 will be created. The default value is 1. Specifying
559 a value of 0 will load bonding, but will not create any devices.
563 Specifies the MII link monitoring frequency in milliseconds.
564 This determines how often the link state of each slave is
565 inspected for link failures. A value of zero disables MII
566 link monitoring. A value of 100 is a good starting point.
567 The use_carrier option, below, affects how the link state is
568 determined. See the High Availability section for additional
569 information. The default value is 100 if arp_interval is not
574 Specifies the minimum number of links that must be active before
575 asserting carrier. It is similar to the Cisco EtherChannel min-links
576 feature. This allows setting the minimum number of member ports that
577 must be up (link-up state) before marking the bond device as up
578 (carrier on). This is useful for situations where higher level services
579 such as clustering want to ensure a minimum number of low bandwidth
580 links are active before switchover. This option only affect 802.3ad
583 The default value is 0. This will cause carrier to be asserted (for
584 802.3ad mode) whenever there is an active aggregator, regardless of the
585 number of available links in that aggregator. Note that, because an
586 aggregator cannot be active without at least one available link,
587 setting this option to 0 or to 1 has the exact same effect.
591 Specifies one of the bonding policies. The default is
592 balance-rr (round robin). Possible values are:
596 Round-robin policy: Transmit packets in sequential
597 order from the first available slave through the
598 last. This mode provides load balancing and fault
603 Active-backup policy: Only one slave in the bond is
604 active. A different slave becomes active if, and only
605 if, the active slave fails. The bond's MAC address is
606 externally visible on only one port (network adapter)
607 to avoid confusing the switch.
609 In bonding version 2.6.2 or later, when a failover
610 occurs in active-backup mode, bonding will issue one
611 or more gratuitous ARPs on the newly active slave.
612 One gratuitous ARP is issued for the bonding master
613 interface and each VLAN interfaces configured above
614 it, provided that the interface has at least one IP
615 address configured. Gratuitous ARPs issued for VLAN
616 interfaces are tagged with the appropriate VLAN id.
618 This mode provides fault tolerance. The primary
619 option, documented below, affects the behavior of this
624 XOR policy: Transmit based on the selected transmit
625 hash policy. The default policy is a simple [(source
626 MAC address XOR'd with destination MAC address XOR
627 packet type ID) modulo slave count]. Alternate transmit
628 policies may be selected via the xmit_hash_policy option,
631 This mode provides load balancing and fault tolerance.
635 Broadcast policy: transmits everything on all slave
636 interfaces. This mode provides fault tolerance.
640 IEEE 802.3ad Dynamic link aggregation. Creates
641 aggregation groups that share the same speed and
642 duplex settings. Utilizes all slaves in the active
643 aggregator according to the 802.3ad specification.
645 Slave selection for outgoing traffic is done according
646 to the transmit hash policy, which may be changed from
647 the default simple XOR policy via the xmit_hash_policy
648 option, documented below. Note that not all transmit
649 policies may be 802.3ad compliant, particularly in
650 regards to the packet mis-ordering requirements of
651 section 43.2.4 of the 802.3ad standard. Differing
652 peer implementations will have varying tolerances for
657 1. Ethtool support in the base drivers for retrieving
658 the speed and duplex of each slave.
660 2. A switch that supports IEEE 802.3ad Dynamic link
663 Most switches will require some type of configuration
664 to enable 802.3ad mode.
668 Adaptive transmit load balancing: channel bonding that
669 does not require any special switch support.
671 In tlb_dynamic_lb=1 mode; the outgoing traffic is
672 distributed according to the current load (computed
673 relative to the speed) on each slave.
675 In tlb_dynamic_lb=0 mode; the load balancing based on
676 current load is disabled and the load is distributed
677 only using the hash distribution.
679 Incoming traffic is received by the current slave.
680 If the receiving slave fails, another slave takes over
681 the MAC address of the failed receiving slave.
685 Ethtool support in the base drivers for retrieving the
690 Adaptive load balancing: includes balance-tlb plus
691 receive load balancing (rlb) for IPV4 traffic, and
692 does not require any special switch support. The
693 receive load balancing is achieved by ARP negotiation.
694 The bonding driver intercepts the ARP Replies sent by
695 the local system on their way out and overwrites the
696 source hardware address with the unique hardware
697 address of one of the slaves in the bond such that
698 different peers use different hardware addresses for
701 Receive traffic from connections created by the server
702 is also balanced. When the local system sends an ARP
703 Request the bonding driver copies and saves the peer's
704 IP information from the ARP packet. When the ARP
705 Reply arrives from the peer, its hardware address is
706 retrieved and the bonding driver initiates an ARP
707 reply to this peer assigning it to one of the slaves
708 in the bond. A problematic outcome of using ARP
709 negotiation for balancing is that each time that an
710 ARP request is broadcast it uses the hardware address
711 of the bond. Hence, peers learn the hardware address
712 of the bond and the balancing of receive traffic
713 collapses to the current slave. This is handled by
714 sending updates (ARP Replies) to all the peers with
715 their individually assigned hardware address such that
716 the traffic is redistributed. Receive traffic is also
717 redistributed when a new slave is added to the bond
718 and when an inactive slave is re-activated. The
719 receive load is distributed sequentially (round robin)
720 among the group of highest speed slaves in the bond.
722 When a link is reconnected or a new slave joins the
723 bond the receive traffic is redistributed among all
724 active slaves in the bond by initiating ARP Replies
725 with the selected MAC address to each of the
726 clients. The updelay parameter (detailed below) must
727 be set to a value equal or greater than the switch's
728 forwarding delay so that the ARP Replies sent to the
729 peers will not be blocked by the switch.
733 1. Ethtool support in the base drivers for retrieving
734 the speed of each slave.
736 2. Base driver support for setting the hardware
737 address of a device while it is open. This is
738 required so that there will always be one slave in the
739 team using the bond hardware address (the
740 curr_active_slave) while having a unique hardware
741 address for each slave in the bond. If the
742 curr_active_slave fails its hardware address is
743 swapped with the new curr_active_slave that was
749 Specify the number of peer notifications (gratuitous ARPs and
750 unsolicited IPv6 Neighbor Advertisements) to be issued after a
751 failover event. As soon as the link is up on the new slave
752 (possibly immediately) a peer notification is sent on the
753 bonding device and each VLAN sub-device. This is repeated at
754 the rate specified by peer_notif_delay if the number is
757 The valid range is 0 - 255; the default value is 1. These options
758 affect only the active-backup mode. These options were added for
759 bonding versions 3.3.0 and 3.4.0 respectively.
761 From Linux 3.0 and bonding version 3.7.1, these notifications
762 are generated by the ipv4 and ipv6 code and the numbers of
763 repetitions cannot be set independently.
767 Specify the number of packets to transmit through a slave before
768 moving to the next one. When set to 0 then a slave is chosen at
771 The valid range is 0 - 65535; the default value is 1. This option
772 has effect only in balance-rr mode.
776 Specify the delay, in milliseconds, between each peer
777 notification (gratuitous ARP and unsolicited IPv6 Neighbor
778 Advertisement) when they are issued after a failover event.
779 This delay should be a multiple of the link monitor interval
780 (arp_interval or miimon, whichever is active). The default
781 value is 0 which means to match the value of the link monitor
785 Slave priority. A higher number means higher priority.
786 The primary slave has the highest priority. This option also
787 follows the primary_reselect rules.
789 This option could only be configured via netlink, and is only valid
790 for active-backup(1), balance-tlb (5) and balance-alb (6) mode.
791 The valid value range is a signed 32 bit integer.
793 The default value is 0.
797 A string (eth0, eth2, etc) specifying which slave is the
798 primary device. The specified device will always be the
799 active slave while it is available. Only when the primary is
800 off-line will alternate devices be used. This is useful when
801 one slave is preferred over another, e.g., when one slave has
802 higher throughput than another.
804 The primary option is only valid for active-backup(1),
805 balance-tlb (5) and balance-alb (6) mode.
809 Specifies the reselection policy for the primary slave. This
810 affects how the primary slave is chosen to become the active slave
811 when failure of the active slave or recovery of the primary slave
812 occurs. This option is designed to prevent flip-flopping between
813 the primary slave and other slaves. Possible values are:
815 always or 0 (default)
817 The primary slave becomes the active slave whenever it
822 The primary slave becomes the active slave when it comes
823 back up, if the speed and duplex of the primary slave is
824 better than the speed and duplex of the current active
829 The primary slave becomes the active slave only if the
830 current active slave fails and the primary slave is up.
832 The primary_reselect setting is ignored in two cases:
834 If no slaves are active, the first slave to recover is
835 made the active slave.
837 When initially enslaved, the primary slave is always made
840 Changing the primary_reselect policy via sysfs will cause an
841 immediate selection of the best active slave according to the new
842 policy. This may or may not result in a change of the active
843 slave, depending upon the circumstances.
845 This option was added for bonding version 3.6.0.
849 Specifies if dynamic shuffling of flows is enabled in tlb
850 or alb mode. The value has no effect on any other modes.
852 The default behavior of tlb mode is to shuffle active flows across
853 slaves based on the load in that interval. This gives nice lb
854 characteristics but can cause packet reordering. If re-ordering is
855 a concern use this variable to disable flow shuffling and rely on
856 load balancing provided solely by the hash distribution.
857 xmit-hash-policy can be used to select the appropriate hashing for
860 The sysfs entry can be used to change the setting per bond device
861 and the initial value is derived from the module parameter. The
862 sysfs entry is allowed to be changed only if the bond device is
865 The default value is "1" that enables flow shuffling while value "0"
866 disables it. This option was added in bonding driver 3.7.1
871 Specifies the time, in milliseconds, to wait before enabling a
872 slave after a link recovery has been detected. This option is
873 only valid for the miimon link monitor. The updelay value
874 should be a multiple of the miimon value; if not, it will be
875 rounded down to the nearest multiple. The default value is 0.
879 Specifies whether or not miimon should use MII or ETHTOOL
880 ioctls vs. netif_carrier_ok() to determine the link
881 status. The MII or ETHTOOL ioctls are less efficient and
882 utilize a deprecated calling sequence within the kernel. The
883 netif_carrier_ok() relies on the device driver to maintain its
884 state with netif_carrier_on/off; at this writing, most, but
885 not all, device drivers support this facility.
887 If bonding insists that the link is up when it should not be,
888 it may be that your network device driver does not support
889 netif_carrier_on/off. The default state for netif_carrier is
890 "carrier on," so if a driver does not support netif_carrier,
891 it will appear as if the link is always up. In this case,
892 setting use_carrier to 0 will cause bonding to revert to the
893 MII / ETHTOOL ioctl method to determine the link state.
895 A value of 1 enables the use of netif_carrier_ok(), a value of
896 0 will use the deprecated MII / ETHTOOL ioctls. The default
901 Selects the transmit hash policy to use for slave selection in
902 balance-xor, 802.3ad, and tlb modes. Possible values are:
906 Uses XOR of hardware MAC addresses and packet type ID
907 field to generate the hash. The formula is
909 hash = source MAC[5] XOR destination MAC[5] XOR packet type ID
910 slave number = hash modulo slave count
912 This algorithm will place all traffic to a particular
913 network peer on the same slave.
915 This algorithm is 802.3ad compliant.
919 This policy uses a combination of layer2 and layer3
920 protocol information to generate the hash.
922 Uses XOR of hardware MAC addresses and IP addresses to
923 generate the hash. The formula is
925 hash = source MAC[5] XOR destination MAC[5] XOR packet type ID
926 hash = hash XOR source IP XOR destination IP
927 hash = hash XOR (hash RSHIFT 16)
928 hash = hash XOR (hash RSHIFT 8)
929 And then hash is reduced modulo slave count.
931 If the protocol is IPv6 then the source and destination
932 addresses are first hashed using ipv6_addr_hash.
934 This algorithm will place all traffic to a particular
935 network peer on the same slave. For non-IP traffic,
936 the formula is the same as for the layer2 transmit
939 This policy is intended to provide a more balanced
940 distribution of traffic than layer2 alone, especially
941 in environments where a layer3 gateway device is
942 required to reach most destinations.
944 This algorithm is 802.3ad compliant.
948 This policy uses upper layer protocol information,
949 when available, to generate the hash. This allows for
950 traffic to a particular network peer to span multiple
951 slaves, although a single connection will not span
954 The formula for unfragmented TCP and UDP packets is
956 hash = source port, destination port (as in the header)
957 hash = hash XOR source IP XOR destination IP
958 hash = hash XOR (hash RSHIFT 16)
959 hash = hash XOR (hash RSHIFT 8)
961 And then hash is reduced modulo slave count.
963 If the protocol is IPv6 then the source and destination
964 addresses are first hashed using ipv6_addr_hash.
966 For fragmented TCP or UDP packets and all other IPv4 and
967 IPv6 protocol traffic, the source and destination port
968 information is omitted. For non-IP traffic, the
969 formula is the same as for the layer2 transmit hash
972 This algorithm is not fully 802.3ad compliant. A
973 single TCP or UDP conversation containing both
974 fragmented and unfragmented packets will see packets
975 striped across two interfaces. This may result in out
976 of order delivery. Most traffic types will not meet
977 this criteria, as TCP rarely fragments traffic, and
978 most UDP traffic is not involved in extended
979 conversations. Other implementations of 802.3ad may
980 or may not tolerate this noncompliance.
984 This policy uses the same formula as layer2+3 but it
985 relies on skb_flow_dissect to obtain the header fields
986 which might result in the use of inner headers if an
987 encapsulation protocol is used. For example this will
988 improve the performance for tunnel users because the
989 packets will be distributed according to the encapsulated
994 This policy uses the same formula as layer3+4 but it
995 relies on skb_flow_dissect to obtain the header fields
996 which might result in the use of inner headers if an
997 encapsulation protocol is used. For example this will
998 improve the performance for tunnel users because the
999 packets will be distributed according to the encapsulated
1004 This policy uses a very rudimentary vlan ID and source mac
1005 hash to load-balance traffic per-vlan, with failover
1006 should one leg fail. The intended use case is for a bond
1007 shared by multiple virtual machines, all configured to
1008 use their own vlan, to give lacp-like functionality
1009 without requiring lacp-capable switching hardware.
1011 The formula for the hash is simply
1013 hash = (vlan ID) XOR (source MAC vendor) XOR (source MAC dev)
1015 The default value is layer2. This option was added in bonding
1016 version 2.6.3. In earlier versions of bonding, this parameter
1017 does not exist, and the layer2 policy is the only policy. The
1018 layer2+3 value was added for bonding version 3.2.2.
1022 Specifies the number of IGMP membership reports to be issued after
1023 a failover event. One membership report is issued immediately after
1024 the failover, subsequent packets are sent in each 200ms interval.
1026 The valid range is 0 - 255; the default value is 1. A value of 0
1027 prevents the IGMP membership report from being issued in response
1028 to the failover event.
1030 This option is useful for bonding modes balance-rr (0), active-backup
1031 (1), balance-tlb (5) and balance-alb (6), in which a failover can
1032 switch the IGMP traffic from one slave to another. Therefore a fresh
1033 IGMP report must be issued to cause the switch to forward the incoming
1034 IGMP traffic over the newly selected slave.
1036 This option was added for bonding version 3.7.0.
1040 Specifies the number of seconds between instances where the bonding
1041 driver sends learning packets to each slaves peer switch.
1043 The valid range is 1 - 0x7fffffff; the default value is 1. This Option
1044 has effect only in balance-tlb and balance-alb modes.
1046 3. Configuring Bonding Devices
1047 ==============================
1049 You can configure bonding using either your distro's network
1050 initialization scripts, or manually using either iproute2 or the
1051 sysfs interface. Distros generally use one of three packages for the
1052 network initialization scripts: initscripts, sysconfig or interfaces.
1053 Recent versions of these packages have support for bonding, while older
1056 We will first describe the options for configuring bonding for
1057 distros using versions of initscripts, sysconfig and interfaces with full
1058 or partial support for bonding, then provide information on enabling
1059 bonding without support from the network initialization scripts (i.e.,
1060 older versions of initscripts or sysconfig).
1062 If you're unsure whether your distro uses sysconfig,
1063 initscripts or interfaces, or don't know if it's new enough, have no fear.
1064 Determining this is fairly straightforward.
1066 First, look for a file called interfaces in /etc/network directory.
1067 If this file is present in your system, then your system use interfaces. See
1068 Configuration with Interfaces Support.
1070 Else, issue the command::
1072 $ rpm -qf /sbin/ifup
1074 It will respond with a line of text starting with either
1075 "initscripts" or "sysconfig," followed by some numbers. This is the
1076 package that provides your network initialization scripts.
1078 Next, to determine if your installation supports bonding,
1081 $ grep ifenslave /sbin/ifup
1083 If this returns any matches, then your initscripts or
1084 sysconfig has support for bonding.
1086 3.1 Configuration with Sysconfig Support
1087 ----------------------------------------
1089 This section applies to distros using a version of sysconfig
1090 with bonding support, for example, SuSE Linux Enterprise Server 9.
1092 SuSE SLES 9's networking configuration system does support
1093 bonding, however, at this writing, the YaST system configuration
1094 front end does not provide any means to work with bonding devices.
1095 Bonding devices can be managed by hand, however, as follows.
1097 First, if they have not already been configured, configure the
1098 slave devices. On SLES 9, this is most easily done by running the
1099 yast2 sysconfig configuration utility. The goal is for to create an
1100 ifcfg-id file for each slave device. The simplest way to accomplish
1101 this is to configure the devices for DHCP (this is only to get the
1102 file ifcfg-id file created; see below for some issues with DHCP). The
1103 name of the configuration file for each device will be of the form::
1105 ifcfg-id-xx:xx:xx:xx:xx:xx
1107 Where the "xx" portion will be replaced with the digits from
1108 the device's permanent MAC address.
1110 Once the set of ifcfg-id-xx:xx:xx:xx:xx:xx files has been
1111 created, it is necessary to edit the configuration files for the slave
1112 devices (the MAC addresses correspond to those of the slave devices).
1113 Before editing, the file will contain multiple lines, and will look
1114 something like this::
1119 UNIQUE='XNzu.WeZGOGF+4wE'
1120 _nm_name='bus-pci-0001:61:01.0'
1122 Change the BOOTPROTO and STARTMODE lines to the following::
1127 Do not alter the UNIQUE or _nm_name lines. Remove any other
1128 lines (USERCTL, etc).
1130 Once the ifcfg-id-xx:xx:xx:xx:xx:xx files have been modified,
1131 it's time to create the configuration file for the bonding device
1132 itself. This file is named ifcfg-bondX, where X is the number of the
1133 bonding device to create, starting at 0. The first such file is
1134 ifcfg-bond0, the second is ifcfg-bond1, and so on. The sysconfig
1135 network configuration system will correctly start multiple instances
1138 The contents of the ifcfg-bondX file is as follows::
1141 BROADCAST="10.0.2.255"
1143 NETMASK="255.255.0.0"
1147 BONDING_MASTER="yes"
1148 BONDING_MODULE_OPTS="mode=active-backup miimon=100"
1149 BONDING_SLAVE0="eth0"
1150 BONDING_SLAVE1="bus-pci-0000:06:08.1"
1152 Replace the sample BROADCAST, IPADDR, NETMASK and NETWORK
1153 values with the appropriate values for your network.
1155 The STARTMODE specifies when the device is brought online.
1156 The possible values are:
1158 ======== ======================================================
1159 onboot The device is started at boot time. If you're not
1160 sure, this is probably what you want.
1162 manual The device is started only when ifup is called
1163 manually. Bonding devices may be configured this
1164 way if you do not wish them to start automatically
1165 at boot for some reason.
1167 hotplug The device is started by a hotplug event. This is not
1168 a valid choice for a bonding device.
1170 off or The device configuration is ignored.
1172 ======== ======================================================
1174 The line BONDING_MASTER='yes' indicates that the device is a
1175 bonding master device. The only useful value is "yes."
1177 The contents of BONDING_MODULE_OPTS are supplied to the
1178 instance of the bonding module for this device. Specify the options
1179 for the bonding mode, link monitoring, and so on here. Do not include
1180 the max_bonds bonding parameter; this will confuse the configuration
1181 system if you have multiple bonding devices.
1183 Finally, supply one BONDING_SLAVEn="slave device" for each
1184 slave. where "n" is an increasing value, one for each slave. The
1185 "slave device" is either an interface name, e.g., "eth0", or a device
1186 specifier for the network device. The interface name is easier to
1187 find, but the ethN names are subject to change at boot time if, e.g.,
1188 a device early in the sequence has failed. The device specifiers
1189 (bus-pci-0000:06:08.1 in the example above) specify the physical
1190 network device, and will not change unless the device's bus location
1191 changes (for example, it is moved from one PCI slot to another). The
1192 example above uses one of each type for demonstration purposes; most
1193 configurations will choose one or the other for all slave devices.
1195 When all configuration files have been modified or created,
1196 networking must be restarted for the configuration changes to take
1197 effect. This can be accomplished via the following::
1199 # /etc/init.d/network restart
1201 Note that the network control script (/sbin/ifdown) will
1202 remove the bonding module as part of the network shutdown processing,
1203 so it is not necessary to remove the module by hand if, e.g., the
1204 module parameters have changed.
1206 Also, at this writing, YaST/YaST2 will not manage bonding
1207 devices (they do not show bonding interfaces on its list of network
1208 devices). It is necessary to edit the configuration file by hand to
1209 change the bonding configuration.
1211 Additional general options and details of the ifcfg file
1212 format can be found in an example ifcfg template file::
1214 /etc/sysconfig/network/ifcfg.template
1216 Note that the template does not document the various ``BONDING_*``
1217 settings described above, but does describe many of the other options.
1219 3.1.1 Using DHCP with Sysconfig
1220 -------------------------------
1222 Under sysconfig, configuring a device with BOOTPROTO='dhcp'
1223 will cause it to query DHCP for its IP address information. At this
1224 writing, this does not function for bonding devices; the scripts
1225 attempt to obtain the device address from DHCP prior to adding any of
1226 the slave devices. Without active slaves, the DHCP requests are not
1227 sent to the network.
1229 3.1.2 Configuring Multiple Bonds with Sysconfig
1230 -----------------------------------------------
1232 The sysconfig network initialization system is capable of
1233 handling multiple bonding devices. All that is necessary is for each
1234 bonding instance to have an appropriately configured ifcfg-bondX file
1235 (as described above). Do not specify the "max_bonds" parameter to any
1236 instance of bonding, as this will confuse sysconfig. If you require
1237 multiple bonding devices with identical parameters, create multiple
1240 Because the sysconfig scripts supply the bonding module
1241 options in the ifcfg-bondX file, it is not necessary to add them to
1242 the system ``/etc/modules.d/*.conf`` configuration files.
1244 3.2 Configuration with Initscripts Support
1245 ------------------------------------------
1247 This section applies to distros using a recent version of
1248 initscripts with bonding support, for example, Red Hat Enterprise Linux
1249 version 3 or later, Fedora, etc. On these systems, the network
1250 initialization scripts have knowledge of bonding, and can be configured to
1251 control bonding devices. Note that older versions of the initscripts
1252 package have lower levels of support for bonding; this will be noted where
1255 These distros will not automatically load the network adapter
1256 driver unless the ethX device is configured with an IP address.
1257 Because of this constraint, users must manually configure a
1258 network-script file for all physical adapters that will be members of
1259 a bondX link. Network script files are located in the directory:
1261 /etc/sysconfig/network-scripts
1263 The file name must be prefixed with "ifcfg-eth" and suffixed
1264 with the adapter's physical adapter number. For example, the script
1265 for eth0 would be named /etc/sysconfig/network-scripts/ifcfg-eth0.
1266 Place the following text in the file::
1275 The DEVICE= line will be different for every ethX device and
1276 must correspond with the name of the file, i.e., ifcfg-eth1 must have
1277 a device line of DEVICE=eth1. The setting of the MASTER= line will
1278 also depend on the final bonding interface name chosen for your bond.
1279 As with other network devices, these typically start at 0, and go up
1280 one for each device, i.e., the first bonding instance is bond0, the
1281 second is bond1, and so on.
1283 Next, create a bond network script. The file name for this
1284 script will be /etc/sysconfig/network-scripts/ifcfg-bondX where X is
1285 the number of the bond. For bond0 the file is named "ifcfg-bond0",
1286 for bond1 it is named "ifcfg-bond1", and so on. Within that file,
1287 place the following text::
1291 NETMASK=255.255.255.0
1293 BROADCAST=192.168.1.255
1298 Be sure to change the networking specific lines (IPADDR,
1299 NETMASK, NETWORK and BROADCAST) to match your network configuration.
1301 For later versions of initscripts, such as that found with Fedora
1302 7 (or later) and Red Hat Enterprise Linux version 5 (or later), it is possible,
1303 and, indeed, preferable, to specify the bonding options in the ifcfg-bond0
1304 file, e.g. a line of the format::
1306 BONDING_OPTS="mode=active-backup arp_interval=60 arp_ip_target=192.168.1.254"
1308 will configure the bond with the specified options. The options
1309 specified in BONDING_OPTS are identical to the bonding module parameters
1310 except for the arp_ip_target field when using versions of initscripts older
1311 than and 8.57 (Fedora 8) and 8.45.19 (Red Hat Enterprise Linux 5.2). When
1312 using older versions each target should be included as a separate option and
1313 should be preceded by a '+' to indicate it should be added to the list of
1314 queried targets, e.g.,::
1316 arp_ip_target=+192.168.1.1 arp_ip_target=+192.168.1.2
1318 is the proper syntax to specify multiple targets. When specifying
1319 options via BONDING_OPTS, it is not necessary to edit
1320 ``/etc/modprobe.d/*.conf``.
1322 For even older versions of initscripts that do not support
1323 BONDING_OPTS, it is necessary to edit /etc/modprobe.d/*.conf, depending upon
1324 your distro) to load the bonding module with your desired options when the
1325 bond0 interface is brought up. The following lines in /etc/modprobe.d/*.conf
1326 will load the bonding module, and select its options:
1329 options bond0 mode=balance-alb miimon=100
1331 Replace the sample parameters with the appropriate set of
1332 options for your configuration.
1334 Finally run "/etc/rc.d/init.d/network restart" as root. This
1335 will restart the networking subsystem and your bond link should be now
1338 3.2.1 Using DHCP with Initscripts
1339 ---------------------------------
1341 Recent versions of initscripts (the versions supplied with Fedora
1342 Core 3 and Red Hat Enterprise Linux 4, or later versions, are reported to
1343 work) have support for assigning IP information to bonding devices via
1346 To configure bonding for DHCP, configure it as described
1347 above, except replace the line "BOOTPROTO=none" with "BOOTPROTO=dhcp"
1348 and add a line consisting of "TYPE=Bonding". Note that the TYPE value
1351 3.2.2 Configuring Multiple Bonds with Initscripts
1352 -------------------------------------------------
1354 Initscripts packages that are included with Fedora 7 and Red Hat
1355 Enterprise Linux 5 support multiple bonding interfaces by simply
1356 specifying the appropriate BONDING_OPTS= in ifcfg-bondX where X is the
1357 number of the bond. This support requires sysfs support in the kernel,
1358 and a bonding driver of version 3.0.0 or later. Other configurations may
1359 not support this method for specifying multiple bonding interfaces; for
1360 those instances, see the "Configuring Multiple Bonds Manually" section,
1363 3.3 Configuring Bonding Manually with iproute2
1364 -----------------------------------------------
1366 This section applies to distros whose network initialization
1367 scripts (the sysconfig or initscripts package) do not have specific
1368 knowledge of bonding. One such distro is SuSE Linux Enterprise Server
1371 The general method for these systems is to place the bonding
1372 module parameters into a config file in /etc/modprobe.d/ (as
1373 appropriate for the installed distro), then add modprobe and/or
1374 `ip link` commands to the system's global init script. The name of
1375 the global init script differs; for sysconfig, it is
1376 /etc/init.d/boot.local and for initscripts it is /etc/rc.d/rc.local.
1378 For example, if you wanted to make a simple bond of two e100
1379 devices (presumed to be eth0 and eth1), and have it persist across
1380 reboots, edit the appropriate file (/etc/init.d/boot.local or
1381 /etc/rc.d/rc.local), and add the following::
1383 modprobe bonding mode=balance-alb miimon=100
1385 ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up
1386 ip link set eth0 master bond0
1387 ip link set eth1 master bond0
1389 Replace the example bonding module parameters and bond0
1390 network configuration (IP address, netmask, etc) with the appropriate
1391 values for your configuration.
1393 Unfortunately, this method will not provide support for the
1394 ifup and ifdown scripts on the bond devices. To reload the bonding
1395 configuration, it is necessary to run the initialization script, e.g.,::
1397 # /etc/init.d/boot.local
1401 # /etc/rc.d/rc.local
1403 It may be desirable in such a case to create a separate script
1404 which only initializes the bonding configuration, then call that
1405 separate script from within boot.local. This allows for bonding to be
1406 enabled without re-running the entire global init script.
1408 To shut down the bonding devices, it is necessary to first
1409 mark the bonding device itself as being down, then remove the
1410 appropriate device driver modules. For our example above, you can do
1413 # ifconfig bond0 down
1417 Again, for convenience, it may be desirable to create a script
1418 with these commands.
1421 3.3.1 Configuring Multiple Bonds Manually
1422 -----------------------------------------
1424 This section contains information on configuring multiple
1425 bonding devices with differing options for those systems whose network
1426 initialization scripts lack support for configuring multiple bonds.
1428 If you require multiple bonding devices, but all with the same
1429 options, you may wish to use the "max_bonds" module parameter,
1432 To create multiple bonding devices with differing options, it is
1433 preferable to use bonding parameters exported by sysfs, documented in the
1436 For versions of bonding without sysfs support, the only means to
1437 provide multiple instances of bonding with differing options is to load
1438 the bonding driver multiple times. Note that current versions of the
1439 sysconfig network initialization scripts handle this automatically; if
1440 your distro uses these scripts, no special action is needed. See the
1441 section Configuring Bonding Devices, above, if you're not sure about your
1442 network initialization scripts.
1444 To load multiple instances of the module, it is necessary to
1445 specify a different name for each instance (the module loading system
1446 requires that every loaded module, even multiple instances of the same
1447 module, have a unique name). This is accomplished by supplying multiple
1448 sets of bonding options in ``/etc/modprobe.d/*.conf``, for example::
1451 options bond0 -o bond0 mode=balance-rr miimon=100
1454 options bond1 -o bond1 mode=balance-alb miimon=50
1456 will load the bonding module two times. The first instance is
1457 named "bond0" and creates the bond0 device in balance-rr mode with an
1458 miimon of 100. The second instance is named "bond1" and creates the
1459 bond1 device in balance-alb mode with an miimon of 50.
1461 In some circumstances (typically with older distributions),
1462 the above does not work, and the second bonding instance never sees
1463 its options. In that case, the second options line can be substituted
1466 install bond1 /sbin/modprobe --ignore-install bonding -o bond1 \
1467 mode=balance-alb miimon=50
1469 This may be repeated any number of times, specifying a new and
1470 unique name in place of bond1 for each subsequent instance.
1472 It has been observed that some Red Hat supplied kernels are unable
1473 to rename modules at load time (the "-o bond1" part). Attempts to pass
1474 that option to modprobe will produce an "Operation not permitted" error.
1475 This has been reported on some Fedora Core kernels, and has been seen on
1476 RHEL 4 as well. On kernels exhibiting this problem, it will be impossible
1477 to configure multiple bonds with differing parameters (as they are older
1478 kernels, and also lack sysfs support).
1480 3.4 Configuring Bonding Manually via Sysfs
1481 ------------------------------------------
1483 Starting with version 3.0.0, Channel Bonding may be configured
1484 via the sysfs interface. This interface allows dynamic configuration
1485 of all bonds in the system without unloading the module. It also
1486 allows for adding and removing bonds at runtime. Ifenslave is no
1487 longer required, though it is still supported.
1489 Use of the sysfs interface allows you to use multiple bonds
1490 with different configurations without having to reload the module.
1491 It also allows you to use multiple, differently configured bonds when
1492 bonding is compiled into the kernel.
1494 You must have the sysfs filesystem mounted to configure
1495 bonding this way. The examples in this document assume that you
1496 are using the standard mount point for sysfs, e.g. /sys. If your
1497 sysfs filesystem is mounted elsewhere, you will need to adjust the
1498 example paths accordingly.
1500 Creating and Destroying Bonds
1501 -----------------------------
1502 To add a new bond foo::
1504 # echo +foo > /sys/class/net/bonding_masters
1506 To remove an existing bond bar::
1508 # echo -bar > /sys/class/net/bonding_masters
1510 To show all existing bonds::
1512 # cat /sys/class/net/bonding_masters
1516 due to 4K size limitation of sysfs files, this list may be
1517 truncated if you have more than a few hundred bonds. This is unlikely
1518 to occur under normal operating conditions.
1520 Adding and Removing Slaves
1521 --------------------------
1522 Interfaces may be enslaved to a bond using the file
1523 /sys/class/net/<bond>/bonding/slaves. The semantics for this file
1524 are the same as for the bonding_masters file.
1526 To enslave interface eth0 to bond bond0::
1529 # echo +eth0 > /sys/class/net/bond0/bonding/slaves
1531 To free slave eth0 from bond bond0::
1533 # echo -eth0 > /sys/class/net/bond0/bonding/slaves
1535 When an interface is enslaved to a bond, symlinks between the
1536 two are created in the sysfs filesystem. In this case, you would get
1537 /sys/class/net/bond0/slave_eth0 pointing to /sys/class/net/eth0, and
1538 /sys/class/net/eth0/master pointing to /sys/class/net/bond0.
1540 This means that you can tell quickly whether or not an
1541 interface is enslaved by looking for the master symlink. Thus:
1542 # echo -eth0 > /sys/class/net/eth0/master/bonding/slaves
1543 will free eth0 from whatever bond it is enslaved to, regardless of
1544 the name of the bond interface.
1546 Changing a Bond's Configuration
1547 -------------------------------
1548 Each bond may be configured individually by manipulating the
1549 files located in /sys/class/net/<bond name>/bonding
1551 The names of these files correspond directly with the command-
1552 line parameters described elsewhere in this file, and, with the
1553 exception of arp_ip_target, they accept the same values. To see the
1554 current setting, simply cat the appropriate file.
1556 A few examples will be given here; for specific usage
1557 guidelines for each parameter, see the appropriate section in this
1560 To configure bond0 for balance-alb mode::
1562 # ifconfig bond0 down
1563 # echo 6 > /sys/class/net/bond0/bonding/mode
1565 # echo balance-alb > /sys/class/net/bond0/bonding/mode
1569 The bond interface must be down before the mode can be changed.
1571 To enable MII monitoring on bond0 with a 1 second interval::
1573 # echo 1000 > /sys/class/net/bond0/bonding/miimon
1577 If ARP monitoring is enabled, it will disabled when MII
1578 monitoring is enabled, and vice-versa.
1580 To add ARP targets::
1582 # echo +192.168.0.100 > /sys/class/net/bond0/bonding/arp_ip_target
1583 # echo +192.168.0.101 > /sys/class/net/bond0/bonding/arp_ip_target
1587 up to 16 target addresses may be specified.
1589 To remove an ARP target::
1591 # echo -192.168.0.100 > /sys/class/net/bond0/bonding/arp_ip_target
1593 To configure the interval between learning packet transmits::
1595 # echo 12 > /sys/class/net/bond0/bonding/lp_interval
1599 the lp_interval is the number of seconds between instances where
1600 the bonding driver sends learning packets to each slaves peer switch. The
1601 default interval is 1 second.
1603 Example Configuration
1604 ---------------------
1605 We begin with the same example that is shown in section 3.3,
1606 executed with sysfs, and without using ifenslave.
1608 To make a simple bond of two e100 devices (presumed to be eth0
1609 and eth1), and have it persist across reboots, edit the appropriate
1610 file (/etc/init.d/boot.local or /etc/rc.d/rc.local), and add the
1615 echo balance-alb > /sys/class/net/bond0/bonding/mode
1616 ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up
1617 echo 100 > /sys/class/net/bond0/bonding/miimon
1618 echo +eth0 > /sys/class/net/bond0/bonding/slaves
1619 echo +eth1 > /sys/class/net/bond0/bonding/slaves
1621 To add a second bond, with two e1000 interfaces in
1622 active-backup mode, using ARP monitoring, add the following lines to
1626 echo +bond1 > /sys/class/net/bonding_masters
1627 echo active-backup > /sys/class/net/bond1/bonding/mode
1628 ifconfig bond1 192.168.2.1 netmask 255.255.255.0 up
1629 echo +192.168.2.100 /sys/class/net/bond1/bonding/arp_ip_target
1630 echo 2000 > /sys/class/net/bond1/bonding/arp_interval
1631 echo +eth2 > /sys/class/net/bond1/bonding/slaves
1632 echo +eth3 > /sys/class/net/bond1/bonding/slaves
1634 3.5 Configuration with Interfaces Support
1635 -----------------------------------------
1637 This section applies to distros which use /etc/network/interfaces file
1638 to describe network interface configuration, most notably Debian and it's
1641 The ifup and ifdown commands on Debian don't support bonding out of
1642 the box. The ifenslave-2.6 package should be installed to provide bonding
1643 support. Once installed, this package will provide ``bond-*`` options
1644 to be used into /etc/network/interfaces.
1646 Note that ifenslave-2.6 package will load the bonding module and use
1647 the ifenslave command when appropriate.
1649 Example Configurations
1650 ----------------------
1652 In /etc/network/interfaces, the following stanza will configure bond0, in
1653 active-backup mode, with eth0 and eth1 as slaves::
1656 iface bond0 inet dhcp
1657 bond-slaves eth0 eth1
1658 bond-mode active-backup
1660 bond-primary eth0 eth1
1662 If the above configuration doesn't work, you might have a system using
1663 upstart for system startup. This is most notably true for recent
1664 Ubuntu versions. The following stanza in /etc/network/interfaces will
1665 produce the same result on those systems::
1668 iface bond0 inet dhcp
1670 bond-mode active-backup
1674 iface eth0 inet manual
1676 bond-primary eth0 eth1
1679 iface eth1 inet manual
1681 bond-primary eth0 eth1
1683 For a full list of ``bond-*`` supported options in /etc/network/interfaces and
1684 some more advanced examples tailored to you particular distros, see the files in
1685 /usr/share/doc/ifenslave-2.6.
1687 3.6 Overriding Configuration for Special Cases
1688 ----------------------------------------------
1690 When using the bonding driver, the physical port which transmits a frame is
1691 typically selected by the bonding driver, and is not relevant to the user or
1692 system administrator. The output port is simply selected using the policies of
1693 the selected bonding mode. On occasion however, it is helpful to direct certain
1694 classes of traffic to certain physical interfaces on output to implement
1695 slightly more complex policies. For example, to reach a web server over a
1696 bonded interface in which eth0 connects to a private network, while eth1
1697 connects via a public network, it may be desirous to bias the bond to send said
1698 traffic over eth0 first, using eth1 only as a fall back, while all other traffic
1699 can safely be sent over either interface. Such configurations may be achieved
1700 using the traffic control utilities inherent in linux.
1702 By default the bonding driver is multiqueue aware and 16 queues are created
1703 when the driver initializes (see Documentation/networking/multiqueue.rst
1704 for details). If more or less queues are desired the module parameter
1705 tx_queues can be used to change this value. There is no sysfs parameter
1706 available as the allocation is done at module init time.
1708 The output of the file /proc/net/bonding/bondX has changed so the output Queue
1709 ID is now printed for each slave::
1711 Bonding Mode: fault-tolerance (active-backup)
1713 Currently Active Slave: eth0
1715 MII Polling Interval (ms): 0
1719 Slave Interface: eth0
1721 Link Failure Count: 0
1722 Permanent HW addr: 00:1a:a0:12:8f:cb
1725 Slave Interface: eth1
1727 Link Failure Count: 0
1728 Permanent HW addr: 00:1a:a0:12:8f:cc
1731 The queue_id for a slave can be set using the command::
1733 # echo "eth1:2" > /sys/class/net/bond0/bonding/queue_id
1735 Any interface that needs a queue_id set should set it with multiple calls
1736 like the one above until proper priorities are set for all interfaces. On
1737 distributions that allow configuration via initscripts, multiple 'queue_id'
1738 arguments can be added to BONDING_OPTS to set all needed slave queues.
1740 These queue id's can be used in conjunction with the tc utility to configure
1741 a multiqueue qdisc and filters to bias certain traffic to transmit on certain
1742 slave devices. For instance, say we wanted, in the above configuration to
1743 force all traffic bound to 192.168.1.100 to use eth1 in the bond as its output
1744 device. The following commands would accomplish this::
1746 # tc qdisc add dev bond0 handle 1 root multiq
1748 # tc filter add dev bond0 protocol ip parent 1: prio 1 u32 match ip \
1749 dst 192.168.1.100 action skbedit queue_mapping 2
1751 These commands tell the kernel to attach a multiqueue queue discipline to the
1752 bond0 interface and filter traffic enqueued to it, such that packets with a dst
1753 ip of 192.168.1.100 have their output queue mapping value overwritten to 2.
1754 This value is then passed into the driver, causing the normal output path
1755 selection policy to be overridden, selecting instead qid 2, which maps to eth1.
1757 Note that qid values begin at 1. Qid 0 is reserved to initiate to the driver
1758 that normal output policy selection should take place. One benefit to simply
1759 leaving the qid for a slave to 0 is the multiqueue awareness in the bonding
1760 driver that is now present. This awareness allows tc filters to be placed on
1761 slave devices as well as bond devices and the bonding driver will simply act as
1762 a pass-through for selecting output queues on the slave device rather than
1763 output port selection.
1765 This feature first appeared in bonding driver version 3.7.0 and support for
1766 output slave selection was limited to round-robin and active-backup modes.
1768 3.7 Configuring LACP for 802.3ad mode in a more secure way
1769 ----------------------------------------------------------
1771 When using 802.3ad bonding mode, the Actor (host) and Partner (switch)
1772 exchange LACPDUs. These LACPDUs cannot be sniffed, because they are
1773 destined to link local mac addresses (which switches/bridges are not
1774 supposed to forward). However, most of the values are easily predictable
1775 or are simply the machine's MAC address (which is trivially known to all
1776 other hosts in the same L2). This implies that other machines in the L2
1777 domain can spoof LACPDU packets from other hosts to the switch and potentially
1778 cause mayhem by joining (from the point of view of the switch) another
1779 machine's aggregate, thus receiving a portion of that hosts incoming
1780 traffic and / or spoofing traffic from that machine themselves (potentially
1781 even successfully terminating some portion of flows). Though this is not
1782 a likely scenario, one could avoid this possibility by simply configuring
1783 few bonding parameters:
1785 (a) ad_actor_system : You can set a random mac-address that can be used for
1786 these LACPDU exchanges. The value can not be either NULL or Multicast.
1787 Also it's preferable to set the local-admin bit. Following shell code
1788 generates a random mac-address as described above::
1790 # sys_mac_addr=$(printf '%02x:%02x:%02x:%02x:%02x:%02x' \
1791 $(( (RANDOM & 0xFE) | 0x02 )) \
1792 $(( RANDOM & 0xFF )) \
1793 $(( RANDOM & 0xFF )) \
1794 $(( RANDOM & 0xFF )) \
1795 $(( RANDOM & 0xFF )) \
1796 $(( RANDOM & 0xFF )))
1797 # echo $sys_mac_addr > /sys/class/net/bond0/bonding/ad_actor_system
1799 (b) ad_actor_sys_prio : Randomize the system priority. The default value
1800 is 65535, but system can take the value from 1 - 65535. Following shell
1801 code generates random priority and sets it::
1803 # sys_prio=$(( 1 + RANDOM + RANDOM ))
1804 # echo $sys_prio > /sys/class/net/bond0/bonding/ad_actor_sys_prio
1806 (c) ad_user_port_key : Use the user portion of the port-key. The default
1807 keeps this empty. These are the upper 10 bits of the port-key and value
1808 ranges from 0 - 1023. Following shell code generates these 10 bits and
1811 # usr_port_key=$(( RANDOM & 0x3FF ))
1812 # echo $usr_port_key > /sys/class/net/bond0/bonding/ad_user_port_key
1815 4 Querying Bonding Configuration
1816 =================================
1818 4.1 Bonding Configuration
1819 -------------------------
1821 Each bonding device has a read-only file residing in the
1822 /proc/net/bonding directory. The file contents include information
1823 about the bonding configuration, options and state of each slave.
1825 For example, the contents of /proc/net/bonding/bond0 after the
1826 driver is loaded with parameters of mode=0 and miimon=1000 is
1827 generally as follows::
1829 Ethernet Channel Bonding Driver: 2.6.1 (October 29, 2004)
1830 Bonding Mode: load balancing (round-robin)
1831 Currently Active Slave: eth0
1833 MII Polling Interval (ms): 1000
1837 Slave Interface: eth1
1839 Link Failure Count: 1
1841 Slave Interface: eth0
1843 Link Failure Count: 1
1845 The precise format and contents will change depending upon the
1846 bonding configuration, state, and version of the bonding driver.
1848 4.2 Network configuration
1849 -------------------------
1851 The network configuration can be inspected using the ifconfig
1852 command. Bonding devices will have the MASTER flag set; Bonding slave
1853 devices will have the SLAVE flag set. The ifconfig output does not
1854 contain information on which slaves are associated with which masters.
1856 In the example below, the bond0 interface is the master
1857 (MASTER) while eth0 and eth1 are slaves (SLAVE). Notice all slaves of
1858 bond0 have the same MAC address (HWaddr) as bond0 for all modes except
1859 TLB and ALB that require a unique MAC address for each slave::
1862 bond0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4
1863 inet addr:XXX.XXX.XXX.YYY Bcast:XXX.XXX.XXX.255 Mask:255.255.252.0
1864 UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1
1865 RX packets:7224794 errors:0 dropped:0 overruns:0 frame:0
1866 TX packets:3286647 errors:1 dropped:0 overruns:1 carrier:0
1867 collisions:0 txqueuelen:0
1869 eth0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4
1870 UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1
1871 RX packets:3573025 errors:0 dropped:0 overruns:0 frame:0
1872 TX packets:1643167 errors:1 dropped:0 overruns:1 carrier:0
1873 collisions:0 txqueuelen:100
1874 Interrupt:10 Base address:0x1080
1876 eth1 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4
1877 UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1
1878 RX packets:3651769 errors:0 dropped:0 overruns:0 frame:0
1879 TX packets:1643480 errors:0 dropped:0 overruns:0 carrier:0
1880 collisions:0 txqueuelen:100
1881 Interrupt:9 Base address:0x1400
1883 5. Switch Configuration
1884 =======================
1886 For this section, "switch" refers to whatever system the
1887 bonded devices are directly connected to (i.e., where the other end of
1888 the cable plugs into). This may be an actual dedicated switch device,
1889 or it may be another regular system (e.g., another computer running
1892 The active-backup, balance-tlb and balance-alb modes do not
1893 require any specific configuration of the switch.
1895 The 802.3ad mode requires that the switch have the appropriate
1896 ports configured as an 802.3ad aggregation. The precise method used
1897 to configure this varies from switch to switch, but, for example, a
1898 Cisco 3550 series switch requires that the appropriate ports first be
1899 grouped together in a single etherchannel instance, then that
1900 etherchannel is set to mode "lacp" to enable 802.3ad (instead of
1901 standard EtherChannel).
1903 The balance-rr, balance-xor and broadcast modes generally
1904 require that the switch have the appropriate ports grouped together.
1905 The nomenclature for such a group differs between switches, it may be
1906 called an "etherchannel" (as in the Cisco example, above), a "trunk
1907 group" or some other similar variation. For these modes, each switch
1908 will also have its own configuration options for the switch's transmit
1909 policy to the bond. Typical choices include XOR of either the MAC or
1910 IP addresses. The transmit policy of the two peers does not need to
1911 match. For these three modes, the bonding mode really selects a
1912 transmit policy for an EtherChannel group; all three will interoperate
1913 with another EtherChannel group.
1916 6. 802.1q VLAN Support
1917 ======================
1919 It is possible to configure VLAN devices over a bond interface
1920 using the 8021q driver. However, only packets coming from the 8021q
1921 driver and passing through bonding will be tagged by default. Self
1922 generated packets, for example, bonding's learning packets or ARP
1923 packets generated by either ALB mode or the ARP monitor mechanism, are
1924 tagged internally by bonding itself. As a result, bonding must
1925 "learn" the VLAN IDs configured above it, and use those IDs to tag
1926 self generated packets.
1928 For reasons of simplicity, and to support the use of adapters
1929 that can do VLAN hardware acceleration offloading, the bonding
1930 interface declares itself as fully hardware offloading capable, it gets
1931 the add_vid/kill_vid notifications to gather the necessary
1932 information, and it propagates those actions to the slaves. In case
1933 of mixed adapter types, hardware accelerated tagged packets that
1934 should go through an adapter that is not offloading capable are
1935 "un-accelerated" by the bonding driver so the VLAN tag sits in the
1938 VLAN interfaces *must* be added on top of a bonding interface
1939 only after enslaving at least one slave. The bonding interface has a
1940 hardware address of 00:00:00:00:00:00 until the first slave is added.
1941 If the VLAN interface is created prior to the first enslavement, it
1942 would pick up the all-zeroes hardware address. Once the first slave
1943 is attached to the bond, the bond device itself will pick up the
1944 slave's hardware address, which is then available for the VLAN device.
1946 Also, be aware that a similar problem can occur if all slaves
1947 are released from a bond that still has one or more VLAN interfaces on
1948 top of it. When a new slave is added, the bonding interface will
1949 obtain its hardware address from the first slave, which might not
1950 match the hardware address of the VLAN interfaces (which was
1951 ultimately copied from an earlier slave).
1953 There are two methods to insure that the VLAN device operates
1954 with the correct hardware address if all slaves are removed from a
1957 1. Remove all VLAN interfaces then recreate them
1959 2. Set the bonding interface's hardware address so that it
1960 matches the hardware address of the VLAN interfaces.
1962 Note that changing a VLAN interface's HW address would set the
1963 underlying device -- i.e. the bonding interface -- to promiscuous
1964 mode, which might not be what you want.
1970 The bonding driver at present supports two schemes for
1971 monitoring a slave device's link state: the ARP monitor and the MII
1974 At the present time, due to implementation restrictions in the
1975 bonding driver itself, it is not possible to enable both ARP and MII
1976 monitoring simultaneously.
1978 7.1 ARP Monitor Operation
1979 -------------------------
1981 The ARP monitor operates as its name suggests: it sends ARP
1982 queries to one or more designated peer systems on the network, and
1983 uses the response as an indication that the link is operating. This
1984 gives some assurance that traffic is actually flowing to and from one
1985 or more peers on the local network.
1987 7.2 Configuring Multiple ARP Targets
1988 ------------------------------------
1990 While ARP monitoring can be done with just one target, it can
1991 be useful in a High Availability setup to have several targets to
1992 monitor. In the case of just one target, the target itself may go
1993 down or have a problem making it unresponsive to ARP requests. Having
1994 an additional target (or several) increases the reliability of the ARP
1997 Multiple ARP targets must be separated by commas as follows::
1999 # example options for ARP monitoring with three targets
2001 options bond0 arp_interval=60 arp_ip_target=192.168.0.1,192.168.0.3,192.168.0.9
2003 For just a single target the options would resemble::
2005 # example options for ARP monitoring with one target
2007 options bond0 arp_interval=60 arp_ip_target=192.168.0.100
2010 7.3 MII Monitor Operation
2011 -------------------------
2013 The MII monitor monitors only the carrier state of the local
2014 network interface. It accomplishes this in one of three ways: by
2015 depending upon the device driver to maintain its carrier state, by
2016 querying the device's MII registers, or by making an ethtool query to
2019 If the use_carrier module parameter is 1 (the default value),
2020 then the MII monitor will rely on the driver for carrier state
2021 information (via the netif_carrier subsystem). As explained in the
2022 use_carrier parameter information, above, if the MII monitor fails to
2023 detect carrier loss on the device (e.g., when the cable is physically
2024 disconnected), it may be that the driver does not support
2027 If use_carrier is 0, then the MII monitor will first query the
2028 device's (via ioctl) MII registers and check the link state. If that
2029 request fails (not just that it returns carrier down), then the MII
2030 monitor will make an ethtool ETHTOOL_GLINK request to attempt to obtain
2031 the same information. If both methods fail (i.e., the driver either
2032 does not support or had some error in processing both the MII register
2033 and ethtool requests), then the MII monitor will assume the link is
2036 8. Potential Sources of Trouble
2037 ===============================
2039 8.1 Adventures in Routing
2040 -------------------------
2042 When bonding is configured, it is important that the slave
2043 devices not have routes that supersede routes of the master (or,
2044 generally, not have routes at all). For example, suppose the bonding
2045 device bond0 has two slaves, eth0 and eth1, and the routing table is
2048 Kernel IP routing table
2049 Destination Gateway Genmask Flags MSS Window irtt Iface
2050 10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth0
2051 10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth1
2052 10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 bond0
2053 127.0.0.0 0.0.0.0 255.0.0.0 U 40 0 0 lo
2055 This routing configuration will likely still update the
2056 receive/transmit times in the driver (needed by the ARP monitor), but
2057 may bypass the bonding driver (because outgoing traffic to, in this
2058 case, another host on network 10 would use eth0 or eth1 before bond0).
2060 The ARP monitor (and ARP itself) may become confused by this
2061 configuration, because ARP requests (generated by the ARP monitor)
2062 will be sent on one interface (bond0), but the corresponding reply
2063 will arrive on a different interface (eth0). This reply looks to ARP
2064 as an unsolicited ARP reply (because ARP matches replies on an
2065 interface basis), and is discarded. The MII monitor is not affected
2066 by the state of the routing table.
2068 The solution here is simply to insure that slaves do not have
2069 routes of their own, and if for some reason they must, those routes do
2070 not supersede routes of their master. This should generally be the
2071 case, but unusual configurations or errant manual or automatic static
2072 route additions may cause trouble.
2074 8.2 Ethernet Device Renaming
2075 ----------------------------
2077 On systems with network configuration scripts that do not
2078 associate physical devices directly with network interface names (so
2079 that the same physical device always has the same "ethX" name), it may
2080 be necessary to add some special logic to config files in
2083 For example, given a modules.conf containing the following::
2086 options bond0 mode=some-mode miimon=50
2092 If neither eth0 and eth1 are slaves to bond0, then when the
2093 bond0 interface comes up, the devices may end up reordered. This
2094 happens because bonding is loaded first, then its slave device's
2095 drivers are loaded next. Since no other drivers have been loaded,
2096 when the e1000 driver loads, it will receive eth0 and eth1 for its
2097 devices, but the bonding configuration tries to enslave eth2 and eth3
2098 (which may later be assigned to the tg3 devices).
2100 Adding the following::
2102 add above bonding e1000 tg3
2104 causes modprobe to load e1000 then tg3, in that order, when
2105 bonding is loaded. This command is fully documented in the
2106 modules.conf manual page.
2108 On systems utilizing modprobe an equivalent problem can occur.
2109 In this case, the following can be added to config files in
2110 /etc/modprobe.d/ as::
2112 softdep bonding pre: tg3 e1000
2114 This will load tg3 and e1000 modules before loading the bonding one.
2115 Full documentation on this can be found in the modprobe.d and modprobe
2118 8.3. Painfully Slow Or No Failed Link Detection By Miimon
2119 ---------------------------------------------------------
2121 By default, bonding enables the use_carrier option, which
2122 instructs bonding to trust the driver to maintain carrier state.
2124 As discussed in the options section, above, some drivers do
2125 not support the netif_carrier_on/_off link state tracking system.
2126 With use_carrier enabled, bonding will always see these links as up,
2127 regardless of their actual state.
2129 Additionally, other drivers do support netif_carrier, but do
2130 not maintain it in real time, e.g., only polling the link state at
2131 some fixed interval. In this case, miimon will detect failures, but
2132 only after some long period of time has expired. If it appears that
2133 miimon is very slow in detecting link failures, try specifying
2134 use_carrier=0 to see if that improves the failure detection time. If
2135 it does, then it may be that the driver checks the carrier state at a
2136 fixed interval, but does not cache the MII register values (so the
2137 use_carrier=0 method of querying the registers directly works). If
2138 use_carrier=0 does not improve the failover, then the driver may cache
2139 the registers, or the problem may be elsewhere.
2141 Also, remember that miimon only checks for the device's
2142 carrier state. It has no way to determine the state of devices on or
2143 beyond other ports of a switch, or if a switch is refusing to pass
2144 traffic while still maintaining carrier on.
2149 If running SNMP agents, the bonding driver should be loaded
2150 before any network drivers participating in a bond. This requirement
2151 is due to the interface index (ipAdEntIfIndex) being associated to
2152 the first interface found with a given IP address. That is, there is
2153 only one ipAdEntIfIndex for each IP address. For example, if eth0 and
2154 eth1 are slaves of bond0 and the driver for eth0 is loaded before the
2155 bonding driver, the interface for the IP address will be associated
2156 with the eth0 interface. This configuration is shown below, the IP
2157 address 192.168.1.1 has an interface index of 2 which indexes to eth0
2158 in the ifDescr table (ifDescr.2).
2162 interfaces.ifTable.ifEntry.ifDescr.1 = lo
2163 interfaces.ifTable.ifEntry.ifDescr.2 = eth0
2164 interfaces.ifTable.ifEntry.ifDescr.3 = eth1
2165 interfaces.ifTable.ifEntry.ifDescr.4 = eth2
2166 interfaces.ifTable.ifEntry.ifDescr.5 = eth3
2167 interfaces.ifTable.ifEntry.ifDescr.6 = bond0
2168 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 5
2169 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2
2170 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 4
2171 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1
2173 This problem is avoided by loading the bonding driver before
2174 any network drivers participating in a bond. Below is an example of
2175 loading the bonding driver first, the IP address 192.168.1.1 is
2176 correctly associated with ifDescr.2.
2178 interfaces.ifTable.ifEntry.ifDescr.1 = lo
2179 interfaces.ifTable.ifEntry.ifDescr.2 = bond0
2180 interfaces.ifTable.ifEntry.ifDescr.3 = eth0
2181 interfaces.ifTable.ifEntry.ifDescr.4 = eth1
2182 interfaces.ifTable.ifEntry.ifDescr.5 = eth2
2183 interfaces.ifTable.ifEntry.ifDescr.6 = eth3
2184 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 6
2185 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2
2186 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 5
2187 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1
2189 While some distributions may not report the interface name in
2190 ifDescr, the association between the IP address and IfIndex remains
2191 and SNMP functions such as Interface_Scan_Next will report that
2194 10. Promiscuous mode
2195 ====================
2197 When running network monitoring tools, e.g., tcpdump, it is
2198 common to enable promiscuous mode on the device, so that all traffic
2199 is seen (instead of seeing only traffic destined for the local host).
2200 The bonding driver handles promiscuous mode changes to the bonding
2201 master device (e.g., bond0), and propagates the setting to the slave
2204 For the balance-rr, balance-xor, broadcast, and 802.3ad modes,
2205 the promiscuous mode setting is propagated to all slaves.
2207 For the active-backup, balance-tlb and balance-alb modes, the
2208 promiscuous mode setting is propagated only to the active slave.
2210 For balance-tlb mode, the active slave is the slave currently
2211 receiving inbound traffic.
2213 For balance-alb mode, the active slave is the slave used as a
2214 "primary." This slave is used for mode-specific control traffic, for
2215 sending to peers that are unassigned or if the load is unbalanced.
2217 For the active-backup, balance-tlb and balance-alb modes, when
2218 the active slave changes (e.g., due to a link failure), the
2219 promiscuous setting will be propagated to the new active slave.
2221 11. Configuring Bonding for High Availability
2222 =============================================
2224 High Availability refers to configurations that provide
2225 maximum network availability by having redundant or backup devices,
2226 links or switches between the host and the rest of the world. The
2227 goal is to provide the maximum availability of network connectivity
2228 (i.e., the network always works), even though other configurations
2229 could provide higher throughput.
2231 11.1 High Availability in a Single Switch Topology
2232 --------------------------------------------------
2234 If two hosts (or a host and a single switch) are directly
2235 connected via multiple physical links, then there is no availability
2236 penalty to optimizing for maximum bandwidth. In this case, there is
2237 only one switch (or peer), so if it fails, there is no alternative
2238 access to fail over to. Additionally, the bonding load balance modes
2239 support link monitoring of their members, so if individual links fail,
2240 the load will be rebalanced across the remaining devices.
2242 See Section 12, "Configuring Bonding for Maximum Throughput"
2243 for information on configuring bonding with one peer device.
2245 11.2 High Availability in a Multiple Switch Topology
2246 ----------------------------------------------------
2248 With multiple switches, the configuration of bonding and the
2249 network changes dramatically. In multiple switch topologies, there is
2250 a trade off between network availability and usable bandwidth.
2252 Below is a sample network, configured to maximize the
2253 availability of the network::
2257 +-----+----+ +-----+----+
2258 | |port2 ISL port2| |
2259 | switch A +--------------------------+ switch B |
2261 +-----+----+ +-----++---+
2264 +-------------+ host1 +---------------+
2267 In this configuration, there is a link between the two
2268 switches (ISL, or inter switch link), and multiple ports connecting to
2269 the outside world ("port3" on each switch). There is no technical
2270 reason that this could not be extended to a third switch.
2272 11.2.1 HA Bonding Mode Selection for Multiple Switch Topology
2273 -------------------------------------------------------------
2275 In a topology such as the example above, the active-backup and
2276 broadcast modes are the only useful bonding modes when optimizing for
2277 availability; the other modes require all links to terminate on the
2278 same peer for them to behave rationally.
2281 This is generally the preferred mode, particularly if
2282 the switches have an ISL and play together well. If the
2283 network configuration is such that one switch is specifically
2284 a backup switch (e.g., has lower capacity, higher cost, etc),
2285 then the primary option can be used to insure that the
2286 preferred link is always used when it is available.
2289 This mode is really a special purpose mode, and is suitable
2290 only for very specific needs. For example, if the two
2291 switches are not connected (no ISL), and the networks beyond
2292 them are totally independent. In this case, if it is
2293 necessary for some specific one-way traffic to reach both
2294 independent networks, then the broadcast mode may be suitable.
2296 11.2.2 HA Link Monitoring Selection for Multiple Switch Topology
2297 ----------------------------------------------------------------
2299 The choice of link monitoring ultimately depends upon your
2300 switch. If the switch can reliably fail ports in response to other
2301 failures, then either the MII or ARP monitors should work. For
2302 example, in the above example, if the "port3" link fails at the remote
2303 end, the MII monitor has no direct means to detect this. The ARP
2304 monitor could be configured with a target at the remote end of port3,
2305 thus detecting that failure without switch support.
2307 In general, however, in a multiple switch topology, the ARP
2308 monitor can provide a higher level of reliability in detecting end to
2309 end connectivity failures (which may be caused by the failure of any
2310 individual component to pass traffic for any reason). Additionally,
2311 the ARP monitor should be configured with multiple targets (at least
2312 one for each switch in the network). This will insure that,
2313 regardless of which switch is active, the ARP monitor has a suitable
2316 Note, also, that of late many switches now support a functionality
2317 generally referred to as "trunk failover." This is a feature of the
2318 switch that causes the link state of a particular switch port to be set
2319 down (or up) when the state of another switch port goes down (or up).
2320 Its purpose is to propagate link failures from logically "exterior" ports
2321 to the logically "interior" ports that bonding is able to monitor via
2322 miimon. Availability and configuration for trunk failover varies by
2323 switch, but this can be a viable alternative to the ARP monitor when using
2326 12. Configuring Bonding for Maximum Throughput
2327 ==============================================
2329 12.1 Maximizing Throughput in a Single Switch Topology
2330 ------------------------------------------------------
2332 In a single switch configuration, the best method to maximize
2333 throughput depends upon the application and network environment. The
2334 various load balancing modes each have strengths and weaknesses in
2335 different environments, as detailed below.
2337 For this discussion, we will break down the topologies into
2338 two categories. Depending upon the destination of most traffic, we
2339 categorize them into either "gatewayed" or "local" configurations.
2341 In a gatewayed configuration, the "switch" is acting primarily
2342 as a router, and the majority of traffic passes through this router to
2343 other networks. An example would be the following::
2346 +----------+ +----------+
2347 | |eth0 port1| | to other networks
2348 | Host A +---------------------+ router +------------------->
2349 | +---------------------+ | Hosts B and C are out
2350 | |eth1 port2| | here somewhere
2351 +----------+ +----------+
2353 The router may be a dedicated router device, or another host
2354 acting as a gateway. For our discussion, the important point is that
2355 the majority of traffic from Host A will pass through the router to
2356 some other network before reaching its final destination.
2358 In a gatewayed network configuration, although Host A may
2359 communicate with many other systems, all of its traffic will be sent
2360 and received via one other peer on the local network, the router.
2362 Note that the case of two systems connected directly via
2363 multiple physical links is, for purposes of configuring bonding, the
2364 same as a gatewayed configuration. In that case, it happens that all
2365 traffic is destined for the "gateway" itself, not some other network
2368 In a local configuration, the "switch" is acting primarily as
2369 a switch, and the majority of traffic passes through this switch to
2370 reach other stations on the same network. An example would be the
2373 +----------+ +----------+ +--------+
2374 | |eth0 port1| +-------+ Host B |
2375 | Host A +------------+ switch |port3 +--------+
2376 | +------------+ | +--------+
2377 | |eth1 port2| +------------------+ Host C |
2378 +----------+ +----------+port4 +--------+
2381 Again, the switch may be a dedicated switch device, or another
2382 host acting as a gateway. For our discussion, the important point is
2383 that the majority of traffic from Host A is destined for other hosts
2384 on the same local network (Hosts B and C in the above example).
2386 In summary, in a gatewayed configuration, traffic to and from
2387 the bonded device will be to the same MAC level peer on the network
2388 (the gateway itself, i.e., the router), regardless of its final
2389 destination. In a local configuration, traffic flows directly to and
2390 from the final destinations, thus, each destination (Host B, Host C)
2391 will be addressed directly by their individual MAC addresses.
2393 This distinction between a gatewayed and a local network
2394 configuration is important because many of the load balancing modes
2395 available use the MAC addresses of the local network source and
2396 destination to make load balancing decisions. The behavior of each
2397 mode is described below.
2400 12.1.1 MT Bonding Mode Selection for Single Switch Topology
2401 -----------------------------------------------------------
2403 This configuration is the easiest to set up and to understand,
2404 although you will have to decide which bonding mode best suits your
2405 needs. The trade offs for each mode are detailed below:
2408 This mode is the only mode that will permit a single
2409 TCP/IP connection to stripe traffic across multiple
2410 interfaces. It is therefore the only mode that will allow a
2411 single TCP/IP stream to utilize more than one interface's
2412 worth of throughput. This comes at a cost, however: the
2413 striping generally results in peer systems receiving packets out
2414 of order, causing TCP/IP's congestion control system to kick
2415 in, often by retransmitting segments.
2417 It is possible to adjust TCP/IP's congestion limits by
2418 altering the net.ipv4.tcp_reordering sysctl parameter. The
2419 usual default value is 3. But keep in mind TCP stack is able
2420 to automatically increase this when it detects reorders.
2422 Note that the fraction of packets that will be delivered out of
2423 order is highly variable, and is unlikely to be zero. The level
2424 of reordering depends upon a variety of factors, including the
2425 networking interfaces, the switch, and the topology of the
2426 configuration. Speaking in general terms, higher speed network
2427 cards produce more reordering (due to factors such as packet
2428 coalescing), and a "many to many" topology will reorder at a
2429 higher rate than a "many slow to one fast" configuration.
2431 Many switches do not support any modes that stripe traffic
2432 (instead choosing a port based upon IP or MAC level addresses);
2433 for those devices, traffic for a particular connection flowing
2434 through the switch to a balance-rr bond will not utilize greater
2435 than one interface's worth of bandwidth.
2437 If you are utilizing protocols other than TCP/IP, UDP for
2438 example, and your application can tolerate out of order
2439 delivery, then this mode can allow for single stream datagram
2440 performance that scales near linearly as interfaces are added
2443 This mode requires the switch to have the appropriate ports
2444 configured for "etherchannel" or "trunking."
2447 There is not much advantage in this network topology to
2448 the active-backup mode, as the inactive backup devices are all
2449 connected to the same peer as the primary. In this case, a
2450 load balancing mode (with link monitoring) will provide the
2451 same level of network availability, but with increased
2452 available bandwidth. On the plus side, active-backup mode
2453 does not require any configuration of the switch, so it may
2454 have value if the hardware available does not support any of
2455 the load balance modes.
2458 This mode will limit traffic such that packets destined
2459 for specific peers will always be sent over the same
2460 interface. Since the destination is determined by the MAC
2461 addresses involved, this mode works best in a "local" network
2462 configuration (as described above), with destinations all on
2463 the same local network. This mode is likely to be suboptimal
2464 if all your traffic is passed through a single router (i.e., a
2465 "gatewayed" network configuration, as described above).
2467 As with balance-rr, the switch ports need to be configured for
2468 "etherchannel" or "trunking."
2471 Like active-backup, there is not much advantage to this
2472 mode in this type of network topology.
2475 This mode can be a good choice for this type of network
2476 topology. The 802.3ad mode is an IEEE standard, so all peers
2477 that implement 802.3ad should interoperate well. The 802.3ad
2478 protocol includes automatic configuration of the aggregates,
2479 so minimal manual configuration of the switch is needed
2480 (typically only to designate that some set of devices is
2481 available for 802.3ad). The 802.3ad standard also mandates
2482 that frames be delivered in order (within certain limits), so
2483 in general single connections will not see misordering of
2484 packets. The 802.3ad mode does have some drawbacks: the
2485 standard mandates that all devices in the aggregate operate at
2486 the same speed and duplex. Also, as with all bonding load
2487 balance modes other than balance-rr, no single connection will
2488 be able to utilize more than a single interface's worth of
2491 Additionally, the linux bonding 802.3ad implementation
2492 distributes traffic by peer (using an XOR of MAC addresses
2493 and packet type ID), so in a "gatewayed" configuration, all
2494 outgoing traffic will generally use the same device. Incoming
2495 traffic may also end up on a single device, but that is
2496 dependent upon the balancing policy of the peer's 802.3ad
2497 implementation. In a "local" configuration, traffic will be
2498 distributed across the devices in the bond.
2500 Finally, the 802.3ad mode mandates the use of the MII monitor,
2501 therefore, the ARP monitor is not available in this mode.
2504 The balance-tlb mode balances outgoing traffic by peer.
2505 Since the balancing is done according to MAC address, in a
2506 "gatewayed" configuration (as described above), this mode will
2507 send all traffic across a single device. However, in a
2508 "local" network configuration, this mode balances multiple
2509 local network peers across devices in a vaguely intelligent
2510 manner (not a simple XOR as in balance-xor or 802.3ad mode),
2511 so that mathematically unlucky MAC addresses (i.e., ones that
2512 XOR to the same value) will not all "bunch up" on a single
2515 Unlike 802.3ad, interfaces may be of differing speeds, and no
2516 special switch configuration is required. On the down side,
2517 in this mode all incoming traffic arrives over a single
2518 interface, this mode requires certain ethtool support in the
2519 network device driver of the slave interfaces, and the ARP
2520 monitor is not available.
2523 This mode is everything that balance-tlb is, and more.
2524 It has all of the features (and restrictions) of balance-tlb,
2525 and will also balance incoming traffic from local network
2526 peers (as described in the Bonding Module Options section,
2529 The only additional down side to this mode is that the network
2530 device driver must support changing the hardware address while
2533 12.1.2 MT Link Monitoring for Single Switch Topology
2534 ----------------------------------------------------
2536 The choice of link monitoring may largely depend upon which
2537 mode you choose to use. The more advanced load balancing modes do not
2538 support the use of the ARP monitor, and are thus restricted to using
2539 the MII monitor (which does not provide as high a level of end to end
2540 assurance as the ARP monitor).
2542 12.2 Maximum Throughput in a Multiple Switch Topology
2543 -----------------------------------------------------
2545 Multiple switches may be utilized to optimize for throughput
2546 when they are configured in parallel as part of an isolated network
2547 between two or more systems, for example::
2553 +--------+ | +---------+
2555 +------+---+ +-----+----+ +-----+----+
2556 | Switch A | | Switch B | | Switch C |
2557 +------+---+ +-----+----+ +-----+----+
2559 +--------+ | +---------+
2565 In this configuration, the switches are isolated from one
2566 another. One reason to employ a topology such as this is for an
2567 isolated network with many hosts (a cluster configured for high
2568 performance, for example), using multiple smaller switches can be more
2569 cost effective than a single larger switch, e.g., on a network with 24
2570 hosts, three 24 port switches can be significantly less expensive than
2571 a single 72 port switch.
2573 If access beyond the network is required, an individual host
2574 can be equipped with an additional network device connected to an
2575 external network; this host then additionally acts as a gateway.
2577 12.2.1 MT Bonding Mode Selection for Multiple Switch Topology
2578 -------------------------------------------------------------
2580 In actual practice, the bonding mode typically employed in
2581 configurations of this type is balance-rr. Historically, in this
2582 network configuration, the usual caveats about out of order packet
2583 delivery are mitigated by the use of network adapters that do not do
2584 any kind of packet coalescing (via the use of NAPI, or because the
2585 device itself does not generate interrupts until some number of
2586 packets has arrived). When employed in this fashion, the balance-rr
2587 mode allows individual connections between two hosts to effectively
2588 utilize greater than one interface's bandwidth.
2590 12.2.2 MT Link Monitoring for Multiple Switch Topology
2591 ------------------------------------------------------
2593 Again, in actual practice, the MII monitor is most often used
2594 in this configuration, as performance is given preference over
2595 availability. The ARP monitor will function in this topology, but its
2596 advantages over the MII monitor are mitigated by the volume of probes
2597 needed as the number of systems involved grows (remember that each
2598 host in the network is configured with bonding).
2600 13. Switch Behavior Issues
2601 ==========================
2603 13.1 Link Establishment and Failover Delays
2604 -------------------------------------------
2606 Some switches exhibit undesirable behavior with regard to the
2607 timing of link up and down reporting by the switch.
2609 First, when a link comes up, some switches may indicate that
2610 the link is up (carrier available), but not pass traffic over the
2611 interface for some period of time. This delay is typically due to
2612 some type of autonegotiation or routing protocol, but may also occur
2613 during switch initialization (e.g., during recovery after a switch
2614 failure). If you find this to be a problem, specify an appropriate
2615 value to the updelay bonding module option to delay the use of the
2616 relevant interface(s).
2618 Second, some switches may "bounce" the link state one or more
2619 times while a link is changing state. This occurs most commonly while
2620 the switch is initializing. Again, an appropriate updelay value may
2623 Note that when a bonding interface has no active links, the
2624 driver will immediately reuse the first link that goes up, even if the
2625 updelay parameter has been specified (the updelay is ignored in this
2626 case). If there are slave interfaces waiting for the updelay timeout
2627 to expire, the interface that first went into that state will be
2628 immediately reused. This reduces down time of the network if the
2629 value of updelay has been overestimated, and since this occurs only in
2630 cases with no connectivity, there is no additional penalty for
2631 ignoring the updelay.
2633 In addition to the concerns about switch timings, if your
2634 switches take a long time to go into backup mode, it may be desirable
2635 to not activate a backup interface immediately after a link goes down.
2636 Failover may be delayed via the downdelay bonding module option.
2638 13.2 Duplicated Incoming Packets
2639 --------------------------------
2641 NOTE: Starting with version 3.0.2, the bonding driver has logic to
2642 suppress duplicate packets, which should largely eliminate this problem.
2643 The following description is kept for reference.
2645 It is not uncommon to observe a short burst of duplicated
2646 traffic when the bonding device is first used, or after it has been
2647 idle for some period of time. This is most easily observed by issuing
2648 a "ping" to some other host on the network, and noticing that the
2649 output from ping flags duplicates (typically one per slave).
2651 For example, on a bond in active-backup mode with five slaves
2652 all connected to one switch, the output may appear as follows::
2655 PING 10.0.4.2 (10.0.4.2) from 10.0.3.10 : 56(84) bytes of data.
2656 64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.7 ms
2657 64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
2658 64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
2659 64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
2660 64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
2661 64 bytes from 10.0.4.2: icmp_seq=2 ttl=64 time=0.216 ms
2662 64 bytes from 10.0.4.2: icmp_seq=3 ttl=64 time=0.267 ms
2663 64 bytes from 10.0.4.2: icmp_seq=4 ttl=64 time=0.222 ms
2665 This is not due to an error in the bonding driver, rather, it
2666 is a side effect of how many switches update their MAC forwarding
2667 tables. Initially, the switch does not associate the MAC address in
2668 the packet with a particular switch port, and so it may send the
2669 traffic to all ports until its MAC forwarding table is updated. Since
2670 the interfaces attached to the bond may occupy multiple ports on a
2671 single switch, when the switch (temporarily) floods the traffic to all
2672 ports, the bond device receives multiple copies of the same packet
2673 (one per slave device).
2675 The duplicated packet behavior is switch dependent, some
2676 switches exhibit this, and some do not. On switches that display this
2677 behavior, it can be induced by clearing the MAC forwarding table (on
2678 most Cisco switches, the privileged command "clear mac address-table
2679 dynamic" will accomplish this).
2681 14. Hardware Specific Considerations
2682 ====================================
2684 This section contains additional information for configuring
2685 bonding on specific hardware platforms, or for interfacing bonding
2686 with particular switches or other devices.
2688 14.1 IBM BladeCenter
2689 --------------------
2691 This applies to the JS20 and similar systems.
2693 On the JS20 blades, the bonding driver supports only
2694 balance-rr, active-backup, balance-tlb and balance-alb modes. This is
2695 largely due to the network topology inside the BladeCenter, detailed
2698 JS20 network adapter information
2699 --------------------------------
2701 All JS20s come with two Broadcom Gigabit Ethernet ports
2702 integrated on the planar (that's "motherboard" in IBM-speak). In the
2703 BladeCenter chassis, the eth0 port of all JS20 blades is hard wired to
2704 I/O Module #1; similarly, all eth1 ports are wired to I/O Module #2.
2705 An add-on Broadcom daughter card can be installed on a JS20 to provide
2706 two more Gigabit Ethernet ports. These ports, eth2 and eth3, are
2707 wired to I/O Modules 3 and 4, respectively.
2709 Each I/O Module may contain either a switch or a passthrough
2710 module (which allows ports to be directly connected to an external
2711 switch). Some bonding modes require a specific BladeCenter internal
2712 network topology in order to function; these are detailed below.
2714 Additional BladeCenter-specific networking information can be
2715 found in two IBM Redbooks (www.ibm.com/redbooks):
2717 - "IBM eServer BladeCenter Networking Options"
2718 - "IBM eServer BladeCenter Layer 2-7 Network Switching"
2720 BladeCenter networking configuration
2721 ------------------------------------
2723 Because a BladeCenter can be configured in a very large number
2724 of ways, this discussion will be confined to describing basic
2727 Normally, Ethernet Switch Modules (ESMs) are used in I/O
2728 modules 1 and 2. In this configuration, the eth0 and eth1 ports of a
2729 JS20 will be connected to different internal switches (in the
2730 respective I/O modules).
2732 A passthrough module (OPM or CPM, optical or copper,
2733 passthrough module) connects the I/O module directly to an external
2734 switch. By using PMs in I/O module #1 and #2, the eth0 and eth1
2735 interfaces of a JS20 can be redirected to the outside world and
2736 connected to a common external switch.
2738 Depending upon the mix of ESMs and PMs, the network will
2739 appear to bonding as either a single switch topology (all PMs) or as a
2740 multiple switch topology (one or more ESMs, zero or more PMs). It is
2741 also possible to connect ESMs together, resulting in a configuration
2742 much like the example in "High Availability in a Multiple Switch
2745 Requirements for specific modes
2746 -------------------------------
2748 The balance-rr mode requires the use of passthrough modules
2749 for devices in the bond, all connected to an common external switch.
2750 That switch must be configured for "etherchannel" or "trunking" on the
2751 appropriate ports, as is usual for balance-rr.
2753 The balance-alb and balance-tlb modes will function with
2754 either switch modules or passthrough modules (or a mix). The only
2755 specific requirement for these modes is that all network interfaces
2756 must be able to reach all destinations for traffic sent over the
2757 bonding device (i.e., the network must converge at some point outside
2760 The active-backup mode has no additional requirements.
2762 Link monitoring issues
2763 ----------------------
2765 When an Ethernet Switch Module is in place, only the ARP
2766 monitor will reliably detect link loss to an external switch. This is
2767 nothing unusual, but examination of the BladeCenter cabinet would
2768 suggest that the "external" network ports are the ethernet ports for
2769 the system, when it fact there is a switch between these "external"
2770 ports and the devices on the JS20 system itself. The MII monitor is
2771 only able to detect link failures between the ESM and the JS20 system.
2773 When a passthrough module is in place, the MII monitor does
2774 detect failures to the "external" port, which is then directly
2775 connected to the JS20 system.
2780 The Serial Over LAN (SoL) link is established over the primary
2781 ethernet (eth0) only, therefore, any loss of link to eth0 will result
2782 in losing your SoL connection. It will not fail over with other
2783 network traffic, as the SoL system is beyond the control of the
2786 It may be desirable to disable spanning tree on the switch
2787 (either the internal Ethernet Switch Module, or an external switch) to
2788 avoid fail-over delay issues when using bonding.
2791 15. Frequently Asked Questions
2792 ==============================
2797 Yes. The old 2.0.xx channel bonding patch was not SMP safe.
2798 The new driver was designed to be SMP safe from the start.
2800 2. What type of cards will work with it?
2801 -----------------------------------------
2803 Any Ethernet type cards (you can even mix cards - a Intel
2804 EtherExpress PRO/100 and a 3com 3c905b, for example). For most modes,
2805 devices need not be of the same speed.
2807 Starting with version 3.2.1, bonding also supports Infiniband
2808 slaves in active-backup mode.
2810 3. How many bonding devices can I have?
2811 ----------------------------------------
2815 4. How many slaves can a bonding device have?
2816 ----------------------------------------------
2818 This is limited only by the number of network interfaces Linux
2819 supports and/or the number of network cards you can place in your
2822 5. What happens when a slave link dies?
2823 ----------------------------------------
2825 If link monitoring is enabled, then the failing device will be
2826 disabled. The active-backup mode will fail over to a backup link, and
2827 other modes will ignore the failed link. The link will continue to be
2828 monitored, and should it recover, it will rejoin the bond (in whatever
2829 manner is appropriate for the mode). See the sections on High
2830 Availability and the documentation for each mode for additional
2833 Link monitoring can be enabled via either the miimon or
2834 arp_interval parameters (described in the module parameters section,
2835 above). In general, miimon monitors the carrier state as sensed by
2836 the underlying network device, and the arp monitor (arp_interval)
2837 monitors connectivity to another host on the local network.
2839 If no link monitoring is configured, the bonding driver will
2840 be unable to detect link failures, and will assume that all links are
2841 always available. This will likely result in lost packets, and a
2842 resulting degradation of performance. The precise performance loss
2843 depends upon the bonding mode and network configuration.
2845 6. Can bonding be used for High Availability?
2846 ----------------------------------------------
2848 Yes. See the section on High Availability for details.
2850 7. Which switches/systems does it work with?
2851 ---------------------------------------------
2853 The full answer to this depends upon the desired mode.
2855 In the basic balance modes (balance-rr and balance-xor), it
2856 works with any system that supports etherchannel (also called
2857 trunking). Most managed switches currently available have such
2858 support, and many unmanaged switches as well.
2860 The advanced balance modes (balance-tlb and balance-alb) do
2861 not have special switch requirements, but do need device drivers that
2862 support specific features (described in the appropriate section under
2863 module parameters, above).
2865 In 802.3ad mode, it works with systems that support IEEE
2866 802.3ad Dynamic Link Aggregation. Most managed and many unmanaged
2867 switches currently available support 802.3ad.
2869 The active-backup mode should work with any Layer-II switch.
2871 8. Where does a bonding device get its MAC address from?
2872 ---------------------------------------------------------
2874 When using slave devices that have fixed MAC addresses, or when
2875 the fail_over_mac option is enabled, the bonding device's MAC address is
2876 the MAC address of the active slave.
2878 For other configurations, if not explicitly configured (with
2879 ifconfig or ip link), the MAC address of the bonding device is taken from
2880 its first slave device. This MAC address is then passed to all following
2881 slaves and remains persistent (even if the first slave is removed) until
2882 the bonding device is brought down or reconfigured.
2884 If you wish to change the MAC address, you can set it with
2885 ifconfig or ip link::
2887 # ifconfig bond0 hw ether 00:11:22:33:44:55
2889 # ip link set bond0 address 66:77:88:99:aa:bb
2891 The MAC address can be also changed by bringing down/up the
2892 device and then changing its slaves (or their order)::
2894 # ifconfig bond0 down ; modprobe -r bonding
2895 # ifconfig bond0 .... up
2896 # ifenslave bond0 eth...
2898 This method will automatically take the address from the next
2899 slave that is added.
2901 To restore your slaves' MAC addresses, you need to detach them
2902 from the bond (``ifenslave -d bond0 eth0``). The bonding driver will
2903 then restore the MAC addresses that the slaves had before they were
2906 16. Resources and Links
2907 =======================
2909 The latest version of the bonding driver can be found in the latest
2910 version of the linux kernel, found on http://kernel.org
2912 The latest version of this document can be found in the latest kernel
2913 source (named Documentation/networking/bonding.rst).
2915 Discussions regarding the development of the bonding driver take place
2916 on the main Linux network mailing list, hosted at vger.kernel.org. The list
2919 netdev@vger.kernel.org
2921 The administrative interface (to subscribe or unsubscribe) can
2924 http://vger.kernel.org/vger-lists.html#netdev