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562d897d DA |
1 | Virtual Routing and Forwarding (VRF) |
2 | ==================================== | |
3 | The VRF device combined with ip rules provides the ability to create virtual | |
4 | routing and forwarding domains (aka VRFs, VRF-lite to be specific) in the | |
5 | Linux network stack. One use case is the multi-tenancy problem where each | |
6 | tenant has their own unique routing tables and in the very least need | |
7 | different default gateways. | |
8 | ||
9 | Processes can be "VRF aware" by binding a socket to the VRF device. Packets | |
10 | through the socket then use the routing table associated with the VRF | |
11 | device. An important feature of the VRF device implementation is that it | |
12 | impacts only Layer 3 and above so L2 tools (e.g., LLDP) are not affected | |
13 | (ie., they do not need to be run in each VRF). The design also allows | |
14 | the use of higher priority ip rules (Policy Based Routing, PBR) to take | |
15 | precedence over the VRF device rules directing specific traffic as desired. | |
16 | ||
17 | In addition, VRF devices allow VRFs to be nested within namespaces. For | |
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18 | example network namespaces provide separation of network interfaces at the |
19 | device layer, VLANs on the interfaces within a namespace provide L2 separation | |
20 | and then VRF devices provide L3 separation. | |
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21 | |
22 | Design | |
23 | ------ | |
24 | A VRF device is created with an associated route table. Network interfaces | |
25 | are then enslaved to a VRF device: | |
26 | ||
27 | +-----------------------------+ | |
28 | | vrf-blue | ===> route table 10 | |
29 | +-----------------------------+ | |
30 | | | | | |
31 | +------+ +------+ +-------------+ | |
32 | | eth1 | | eth2 | ... | bond1 | | |
33 | +------+ +------+ +-------------+ | |
34 | | | | |
35 | +------+ +------+ | |
36 | | eth8 | | eth9 | | |
37 | +------+ +------+ | |
38 | ||
39 | Packets received on an enslaved device and are switched to the VRF device | |
6e076537 DA |
40 | in the IPv4 and IPv6 processing stacks giving the impression that packets |
41 | flow through the VRF device. Similarly on egress routing rules are used to | |
42 | send packets to the VRF device driver before getting sent out the actual | |
43 | interface. This allows tcpdump on a VRF device to capture all packets into | |
44 | and out of the VRF as a whole.[1] Similarly, netfilter[2] and tc rules can be | |
45 | applied using the VRF device to specify rules that apply to the VRF domain | |
46 | as a whole. | |
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47 | |
48 | [1] Packets in the forwarded state do not flow through the device, so those | |
49 | packets are not seen by tcpdump. Will revisit this limitation in a | |
50 | future release. | |
51 | ||
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52 | [2] Iptables on ingress supports PREROUTING with skb->dev set to the real |
53 | ingress device and both INPUT and PREROUTING rules with skb->dev set to | |
54 | the VRF device. For egress POSTROUTING and OUTPUT rules can be written | |
55 | using either the VRF device or real egress device. | |
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56 | |
57 | Setup | |
58 | ----- | |
59 | 1. VRF device is created with an association to a FIB table. | |
60 | e.g, ip link add vrf-blue type vrf table 10 | |
61 | ip link set dev vrf-blue up | |
62 | ||
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63 | 2. An l3mdev FIB rule directs lookups to the table associated with the device. |
64 | A single l3mdev rule is sufficient for all VRFs. The VRF device adds the | |
65 | l3mdev rule for IPv4 and IPv6 when the first device is created with a | |
66 | default preference of 1000. Users may delete the rule if desired and add | |
67 | with a different priority or install per-VRF rules. | |
68 | ||
69 | Prior to the v4.8 kernel iif and oif rules are needed for each VRF device: | |
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70 | ip ru add oif vrf-blue table 10 |
71 | ip ru add iif vrf-blue table 10 | |
72 | ||
6e076537 | 73 | 3. Set the default route for the table (and hence default route for the VRF). |
17c91884 DS |
74 | ip route add table 10 unreachable default metric 4278198272 |
75 | ||
76 | This high metric value ensures that the default unreachable route can | |
77 | be overridden by a routing protocol suite. FRRouting interprets | |
78 | kernel metrics as a combined admin distance (upper byte) and priority | |
79 | (lower 3 bytes). Thus the above metric translates to [255/8192]. | |
562d897d | 80 | |
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81 | 4. Enslave L3 interfaces to a VRF device. |
82 | ip link set dev eth1 master vrf-blue | |
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83 | |
84 | Local and connected routes for enslaved devices are automatically moved to | |
85 | the table associated with VRF device. Any additional routes depending on | |
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86 | the enslaved device are dropped and will need to be reinserted to the VRF |
87 | FIB table following the enslavement. | |
88 | ||
89 | The IPv6 sysctl option keep_addr_on_down can be enabled to keep IPv6 global | |
90 | addresses as VRF enslavement changes. | |
91 | sysctl -w net.ipv6.conf.all.keep_addr_on_down=1 | |
562d897d | 92 | |
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93 | 5. Additional VRF routes are added to associated table. |
94 | ip route add table 10 ... | |
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95 | |
96 | ||
97 | Applications | |
98 | ------------ | |
99 | Applications that are to work within a VRF need to bind their socket to the | |
100 | VRF device: | |
101 | ||
102 | setsockopt(sd, SOL_SOCKET, SO_BINDTODEVICE, dev, strlen(dev)+1); | |
103 | ||
104 | or to specify the output device using cmsg and IP_PKTINFO. | |
105 | ||
3c82a21f RS |
106 | By default the scope of the port bindings for unbound sockets is |
107 | limited to the default VRF. That is, it will not be matched by packets | |
108 | arriving on interfaces enslaved to an l3mdev and processes may bind to | |
109 | the same port if they bind to an l3mdev. | |
110 | ||
63a6fff3 RS |
111 | TCP & UDP services running in the default VRF context (ie., not bound |
112 | to any VRF device) can work across all VRF domains by enabling the | |
113 | tcp_l3mdev_accept and udp_l3mdev_accept sysctl options: | |
6897445f | 114 | |
6e076537 | 115 | sysctl -w net.ipv4.tcp_l3mdev_accept=1 |
63a6fff3 | 116 | sysctl -w net.ipv4.udp_l3mdev_accept=1 |
562d897d | 117 | |
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118 | These options are disabled by default so that a socket in a VRF is only |
119 | selected for packets in that VRF. There is a similar option for RAW | |
120 | sockets, which is enabled by default for reasons of backwards compatibility. | |
121 | This is so as to specify the output device with cmsg and IP_PKTINFO, but | |
122 | using a socket not bound to the corresponding VRF. This allows e.g. older ping | |
123 | implementations to be run with specifying the device but without executing it | |
124 | in the VRF. This option can be disabled so that packets received in a VRF | |
125 | context are only handled by a raw socket bound to the VRF, and packets in the | |
126 | default VRF are only handled by a socket not bound to any VRF: | |
127 | ||
128 | sysctl -w net.ipv4.raw_l3mdev_accept=0 | |
129 | ||
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130 | netfilter rules on the VRF device can be used to limit access to services |
131 | running in the default VRF context as well. | |
132 | ||
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133 | ################################################################################ |
134 | ||
135 | Using iproute2 for VRFs | |
136 | ======================= | |
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137 | iproute2 supports the vrf keyword as of v4.7. For backwards compatibility this |
138 | section lists both commands where appropriate -- with the vrf keyword and the | |
139 | older form without it. | |
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140 | |
141 | 1. Create a VRF | |
142 | ||
143 | To instantiate a VRF device and associate it with a table: | |
144 | $ ip link add dev NAME type vrf table ID | |
145 | ||
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146 | As of v4.8 the kernel supports the l3mdev FIB rule where a single rule |
147 | covers all VRFs. The l3mdev rule is created for IPv4 and IPv6 on first | |
148 | device create. | |
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149 | |
150 | 2. List VRFs | |
151 | ||
152 | To list VRFs that have been created: | |
153 | $ ip [-d] link show type vrf | |
154 | NOTE: The -d option is needed to show the table id | |
155 | ||
156 | For example: | |
157 | $ ip -d link show type vrf | |
6e076537 | 158 | 11: mgmt: <NOARP,MASTER,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000 |
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159 | link/ether 72:b3:ba:91:e2:24 brd ff:ff:ff:ff:ff:ff promiscuity 0 |
160 | vrf table 1 addrgenmode eui64 | |
6e076537 | 161 | 12: red: <NOARP,MASTER,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000 |
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162 | link/ether b6:6f:6e:f6:da:73 brd ff:ff:ff:ff:ff:ff promiscuity 0 |
163 | vrf table 10 addrgenmode eui64 | |
6e076537 | 164 | 13: blue: <NOARP,MASTER,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000 |
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165 | link/ether 36:62:e8:7d:bb:8c brd ff:ff:ff:ff:ff:ff promiscuity 0 |
166 | vrf table 66 addrgenmode eui64 | |
6e076537 | 167 | 14: green: <NOARP,MASTER,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000 |
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168 | link/ether e6:28:b8:63:70:bb brd ff:ff:ff:ff:ff:ff promiscuity 0 |
169 | vrf table 81 addrgenmode eui64 | |
170 | ||
171 | ||
172 | Or in brief output: | |
173 | ||
174 | $ ip -br link show type vrf | |
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175 | mgmt UP 72:b3:ba:91:e2:24 <NOARP,MASTER,UP,LOWER_UP> |
176 | red UP b6:6f:6e:f6:da:73 <NOARP,MASTER,UP,LOWER_UP> | |
177 | blue UP 36:62:e8:7d:bb:8c <NOARP,MASTER,UP,LOWER_UP> | |
178 | green UP e6:28:b8:63:70:bb <NOARP,MASTER,UP,LOWER_UP> | |
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179 | |
180 | ||
181 | 3. Assign a Network Interface to a VRF | |
182 | ||
183 | Network interfaces are assigned to a VRF by enslaving the netdevice to a | |
184 | VRF device: | |
6e076537 | 185 | $ ip link set dev NAME master NAME |
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186 | |
187 | On enslavement connected and local routes are automatically moved to the | |
188 | table associated with the VRF device. | |
189 | ||
190 | For example: | |
6e076537 | 191 | $ ip link set dev eth0 master mgmt |
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192 | |
193 | ||
194 | 4. Show Devices Assigned to a VRF | |
195 | ||
196 | To show devices that have been assigned to a specific VRF add the master | |
197 | option to the ip command: | |
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198 | $ ip link show vrf NAME |
199 | $ ip link show master NAME | |
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200 | |
201 | For example: | |
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202 | $ ip link show vrf red |
203 | 3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master red state UP mode DEFAULT group default qlen 1000 | |
4b418bff | 204 | link/ether 02:00:00:00:02:02 brd ff:ff:ff:ff:ff:ff |
6e076537 | 205 | 4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master red state UP mode DEFAULT group default qlen 1000 |
4b418bff | 206 | link/ether 02:00:00:00:02:03 brd ff:ff:ff:ff:ff:ff |
6e076537 | 207 | 7: eth5: <BROADCAST,MULTICAST> mtu 1500 qdisc noop master red state DOWN mode DEFAULT group default qlen 1000 |
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208 | link/ether 02:00:00:00:02:06 brd ff:ff:ff:ff:ff:ff |
209 | ||
210 | ||
211 | Or using the brief output: | |
484f674b | 212 | $ ip -br link show vrf red |
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213 | eth1 UP 02:00:00:00:02:02 <BROADCAST,MULTICAST,UP,LOWER_UP> |
214 | eth2 UP 02:00:00:00:02:03 <BROADCAST,MULTICAST,UP,LOWER_UP> | |
215 | eth5 DOWN 02:00:00:00:02:06 <BROADCAST,MULTICAST> | |
216 | ||
217 | ||
218 | 5. Show Neighbor Entries for a VRF | |
219 | ||
220 | To list neighbor entries associated with devices enslaved to a VRF device | |
221 | add the master option to the ip command: | |
6e076537 DA |
222 | $ ip [-6] neigh show vrf NAME |
223 | $ ip [-6] neigh show master NAME | |
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224 | |
225 | For example: | |
6e076537 | 226 | $ ip neigh show vrf red |
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227 | 10.2.1.254 dev eth1 lladdr a6:d9:c7:4f:06:23 REACHABLE |
228 | 10.2.2.254 dev eth2 lladdr 5e:54:01:6a:ee:80 REACHABLE | |
229 | ||
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230 | $ ip -6 neigh show vrf red |
231 | 2002:1::64 dev eth1 lladdr a6:d9:c7:4f:06:23 REACHABLE | |
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232 | |
233 | ||
234 | 6. Show Addresses for a VRF | |
235 | ||
236 | To show addresses for interfaces associated with a VRF add the master | |
237 | option to the ip command: | |
6e076537 DA |
238 | $ ip addr show vrf NAME |
239 | $ ip addr show master NAME | |
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240 | |
241 | For example: | |
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242 | $ ip addr show vrf red |
243 | 3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master red state UP group default qlen 1000 | |
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244 | link/ether 02:00:00:00:02:02 brd ff:ff:ff:ff:ff:ff |
245 | inet 10.2.1.2/24 brd 10.2.1.255 scope global eth1 | |
246 | valid_lft forever preferred_lft forever | |
247 | inet6 2002:1::2/120 scope global | |
248 | valid_lft forever preferred_lft forever | |
249 | inet6 fe80::ff:fe00:202/64 scope link | |
250 | valid_lft forever preferred_lft forever | |
6e076537 | 251 | 4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master red state UP group default qlen 1000 |
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252 | link/ether 02:00:00:00:02:03 brd ff:ff:ff:ff:ff:ff |
253 | inet 10.2.2.2/24 brd 10.2.2.255 scope global eth2 | |
254 | valid_lft forever preferred_lft forever | |
255 | inet6 2002:2::2/120 scope global | |
256 | valid_lft forever preferred_lft forever | |
257 | inet6 fe80::ff:fe00:203/64 scope link | |
258 | valid_lft forever preferred_lft forever | |
6e076537 | 259 | 7: eth5: <BROADCAST,MULTICAST> mtu 1500 qdisc noop master red state DOWN group default qlen 1000 |
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260 | link/ether 02:00:00:00:02:06 brd ff:ff:ff:ff:ff:ff |
261 | ||
262 | Or in brief format: | |
6e076537 | 263 | $ ip -br addr show vrf red |
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264 | eth1 UP 10.2.1.2/24 2002:1::2/120 fe80::ff:fe00:202/64 |
265 | eth2 UP 10.2.2.2/24 2002:2::2/120 fe80::ff:fe00:203/64 | |
266 | eth5 DOWN | |
267 | ||
268 | ||
269 | 7. Show Routes for a VRF | |
270 | ||
271 | To show routes for a VRF use the ip command to display the table associated | |
272 | with the VRF device: | |
6e076537 | 273 | $ ip [-6] route show vrf NAME |
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274 | $ ip [-6] route show table ID |
275 | ||
276 | For example: | |
6e076537 | 277 | $ ip route show vrf red |
17c91884 | 278 | unreachable default metric 4278198272 |
4b418bff DA |
279 | broadcast 10.2.1.0 dev eth1 proto kernel scope link src 10.2.1.2 |
280 | 10.2.1.0/24 dev eth1 proto kernel scope link src 10.2.1.2 | |
281 | local 10.2.1.2 dev eth1 proto kernel scope host src 10.2.1.2 | |
282 | broadcast 10.2.1.255 dev eth1 proto kernel scope link src 10.2.1.2 | |
283 | broadcast 10.2.2.0 dev eth2 proto kernel scope link src 10.2.2.2 | |
284 | 10.2.2.0/24 dev eth2 proto kernel scope link src 10.2.2.2 | |
285 | local 10.2.2.2 dev eth2 proto kernel scope host src 10.2.2.2 | |
286 | broadcast 10.2.2.255 dev eth2 proto kernel scope link src 10.2.2.2 | |
287 | ||
6e076537 | 288 | $ ip -6 route show vrf red |
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289 | local 2002:1:: dev lo proto none metric 0 pref medium |
290 | local 2002:1::2 dev lo proto none metric 0 pref medium | |
291 | 2002:1::/120 dev eth1 proto kernel metric 256 pref medium | |
292 | local 2002:2:: dev lo proto none metric 0 pref medium | |
293 | local 2002:2::2 dev lo proto none metric 0 pref medium | |
294 | 2002:2::/120 dev eth2 proto kernel metric 256 pref medium | |
295 | local fe80:: dev lo proto none metric 0 pref medium | |
296 | local fe80:: dev lo proto none metric 0 pref medium | |
297 | local fe80::ff:fe00:202 dev lo proto none metric 0 pref medium | |
298 | local fe80::ff:fe00:203 dev lo proto none metric 0 pref medium | |
299 | fe80::/64 dev eth1 proto kernel metric 256 pref medium | |
300 | fe80::/64 dev eth2 proto kernel metric 256 pref medium | |
6e076537 | 301 | ff00::/8 dev red metric 256 pref medium |
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302 | ff00::/8 dev eth1 metric 256 pref medium |
303 | ff00::/8 dev eth2 metric 256 pref medium | |
17c91884 | 304 | unreachable default dev lo metric 4278198272 error -101 pref medium |
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305 | |
306 | 8. Route Lookup for a VRF | |
307 | ||
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308 | A test route lookup can be done for a VRF: |
309 | $ ip [-6] route get vrf NAME ADDRESS | |
310 | $ ip [-6] route get oif NAME ADDRESS | |
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311 | |
312 | For example: | |
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313 | $ ip route get 10.2.1.40 vrf red |
314 | 10.2.1.40 dev eth1 table red src 10.2.1.2 | |
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315 | cache |
316 | ||
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317 | $ ip -6 route get 2002:1::32 vrf red |
318 | 2002:1::32 from :: dev eth1 table red proto kernel src 2002:1::2 metric 256 pref medium | |
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319 | |
320 | ||
321 | 9. Removing Network Interface from a VRF | |
322 | ||
323 | Network interfaces are removed from a VRF by breaking the enslavement to | |
324 | the VRF device: | |
325 | $ ip link set dev NAME nomaster | |
326 | ||
327 | Connected routes are moved back to the default table and local entries are | |
328 | moved to the local table. | |
329 | ||
330 | For example: | |
331 | $ ip link set dev eth0 nomaster | |
332 | ||
333 | -------------------------------------------------------------------------------- | |
334 | ||
335 | Commands used in this example: | |
336 | ||
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337 | cat >> /etc/iproute2/rt_tables.d/vrf.conf <<EOF |
338 | 1 mgmt | |
339 | 10 red | |
340 | 66 blue | |
341 | 81 green | |
4b418bff DA |
342 | EOF |
343 | ||
344 | function vrf_create | |
345 | { | |
346 | VRF=$1 | |
347 | TBID=$2 | |
4b418bff | 348 | |
6e076537 DA |
349 | # create VRF device |
350 | ip link add ${VRF} type vrf table ${TBID} | |
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351 | |
352 | if [ "${VRF}" != "mgmt" ]; then | |
17c91884 | 353 | ip route add table ${TBID} unreachable default metric 4278198272 |
4b418bff | 354 | fi |
6e076537 | 355 | ip link set dev ${VRF} up |
4b418bff DA |
356 | } |
357 | ||
358 | vrf_create mgmt 1 | |
6e076537 | 359 | ip link set dev eth0 master mgmt |
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360 | |
361 | vrf_create red 10 | |
6e076537 DA |
362 | ip link set dev eth1 master red |
363 | ip link set dev eth2 master red | |
364 | ip link set dev eth5 master red | |
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365 | |
366 | vrf_create blue 66 | |
6e076537 | 367 | ip link set dev eth3 master blue |
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368 | |
369 | vrf_create green 81 | |
6e076537 | 370 | ip link set dev eth4 master green |
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371 | |
372 | ||
373 | Interface addresses from /etc/network/interfaces: | |
374 | auto eth0 | |
375 | iface eth0 inet static | |
376 | address 10.0.0.2 | |
377 | netmask 255.255.255.0 | |
378 | gateway 10.0.0.254 | |
379 | ||
380 | iface eth0 inet6 static | |
381 | address 2000:1::2 | |
382 | netmask 120 | |
383 | ||
384 | auto eth1 | |
385 | iface eth1 inet static | |
386 | address 10.2.1.2 | |
387 | netmask 255.255.255.0 | |
388 | ||
389 | iface eth1 inet6 static | |
390 | address 2002:1::2 | |
391 | netmask 120 | |
392 | ||
393 | auto eth2 | |
394 | iface eth2 inet static | |
395 | address 10.2.2.2 | |
396 | netmask 255.255.255.0 | |
397 | ||
398 | iface eth2 inet6 static | |
399 | address 2002:2::2 | |
400 | netmask 120 | |
401 | ||
402 | auto eth3 | |
403 | iface eth3 inet static | |
404 | address 10.2.3.2 | |
405 | netmask 255.255.255.0 | |
406 | ||
407 | iface eth3 inet6 static | |
408 | address 2002:3::2 | |
409 | netmask 120 | |
410 | ||
411 | auto eth4 | |
412 | iface eth4 inet static | |
413 | address 10.2.4.2 | |
414 | netmask 255.255.255.0 | |
415 | ||
416 | iface eth4 inet6 static | |
417 | address 2002:4::2 | |
418 | netmask 120 |