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Example: Nonforwarding Instances Configuration
In Figure 1, routers CE1, CE2, CE3, and CE4 are CE routers, PE0 and PE2 are PE routers, and Router P is the provider core transit router. CE1 and CE3 are part of a “community of interest” group called data, whereas CE2 and CE4 belong to a group called voice. Your goal is to connect the members of each group to each other by using a nonforwarding instance at the PE routers.
Note that routers PE0, CE1, and CE2 mirror the configurations on PE2, CE3, and CE4, respectively. Therefore, the latter routers are not shown in this example. The loopback addressing scheme for this network is shown in Table 1.
Table 1: Nonforwarding Instances—Loopback Addresses
Router | Loopback Address |
---|---|
CE1 | 10.255.255.172 |
CE2 | 10.255.255.180 |
PE0 | 10.255.255.176 |
P | 10.255.255.178 |
PE2 | 10.255.255.174 |
CE3 | 10.255.255.182 |
CE4 | 10.255.255.181 |
Routers CE1, CE2, CE3, and CE4 only need basic connectivity to their directly connected PE router. You enable OSPF on the interface that connects the CE routers to the PE routers. Since the configurations for all the CE routers are almost identical, only CE3 and CE4 are shown.
Router CE3
Router CE4
PE router configuration is next. Because the configuration for Router PE0 and Router PE2 mirror each other, only Router PE2 is displayed.
You must enable the auto-export statement at the edit-routing-options hierarchy level for both the main configuration and the nonforwarding instances, establish policies that set tags on packets arriving from the CE routers, and accept packets into a specific instance that matches the corresponding outbound tags. Specifically, you configure the router to attach adata tag to all packets coming from Router CE3 and avoicetag to all packets arriving from Router CE4. Also, forward any OSPF traffic coming from the core with adata tag to Router CE3: send OSPF core traffic with avoicetag to Router CE4.
Router PE2
On Router P, the provider core router configuration is simple. Include the interfaces that connect to the two PE routers (PE0 and PE2) in the OSPF process.
Router P
If all the configurations are correct, routers CE1 and CE3 (the routers tagged with thedatatag ) can send traffic to one another and routers CE2 and CE4 (the routers tagged with thevoice tag ) can communicate bidirectionally, but routers with different tag types cannot reach each other.
Verifying Your Work
To verify that the nonforwarding instances configuration is functioning properly, you can use the following commands:
show ospf database
show route detail
ping
The following sections show the output of these commands used with the configuration example:
Router PE2 Status
user@PE2> show ospf database
OSPF link state database, area 0.0.0.0 Type ID Adv Rtr Seq Age Opt Cksum Len Router *10.255.255.174 10.255.255.174 0x80000014 180 0x2 0x14b3 60 Router 10.255.255.176 10.255.255.176 0x80000010 592 0x2 0x14c1 60 Router 10.255.255.178 10.255.255.178 0x80000007 1074 0x2 0x9329 84 OSPF AS SCOPE link state database Type ID Adv Rtr Seq Age Opt Cksum Len Extern 10.255.255.172 10.255.255.176 0x8000000f 489 0x2 0xd258 36 Extern 10.255.255.180 10.255.255.176 0x8000000f 189 0x2 0x948d 36 Extern *10.255.255.181 10.255.255.174 0x8000000f 780 0x2 0x968c 36 Extern *10.255.255.182 10.255.255.174 0x8000000f 480 0x2 0x7aa8 36 user@PE2> show ospf database instance voice OSPF link state database, area 0.0.0.0 Type ID Adv Rtr Seq Age Opt Cksum Len Router 10.255.255.181 10.255.255.181 0x80000008 1112 0x2 0x29ac 60 Router *192.255.197.117 192.255.197.117 0x8000000c 2681 0x2 0x5d7a 48 OSPF AS SCOPE link state database Type ID Adv Rtr Seq Age Opt Cksum Len Extern *10.255.255.180 192.255.197.117 0x80000001 2681 0x2 0x5cf7 36 user@PE2> show ospf database instance data OSPF link state database, area 0.0.0.0 Type ID Adv Rtr Seq Age Opt Cksum Len Router 10.255.255.182 10.255.255.182 0x8000000b 1117 0x2 0x53d 60 Router *192.255.197.249 192.255.197.249 0x8000000e 2686 0x2 0xbd05 48 OSPF AS SCOPE link state database Type ID Adv Rtr Seq Age Opt Cksum Len Extern *10.255.255.172 192.255.197.249 0x80000002 2686 0x2 0x7d5a 36
Router CE3 Status
user@CE3> ping 10.255.255.172
PING 10.255.255.172 (10.255.255.172): 56 data bytes 64 bytes from 10.255.255.172: icmp_seq=0 ttl=252 time=2.978 ms 64 bytes from 10.255.255.172: icmp_seq=1 ttl=252 time=2.903 ms ^C --- 10.255.255.172 ping statistics --- 2 packets transmitted, 2 packets received, 0% packet loss round-trip min/avg/max/stddev = 2.903/2.941/2.978/0.037 ms user@CE3> ping 10.255.255.180 PING 10.255.255.180 (10.255.255.180): 56 data bytes ^C --- 10.255.255.180 ping statistics --- 2 packets transmitted, 0 packets received, 100% packet loss user@CE3> show ospf database OSPF link state database, area 0.0.0.0 Type ID Adv Rtr Seq Age Opt Cksum Len Router *10.255.255.182 10.255.255.182 0x8000000b 1164 0x2 0x53d 60 Router 192.255.197.249 192.255.197.249 0x8000000e 2735 0x2 0xbd05 48 OSPF AS SCOPE link state database Type ID Adv Rtr Seq Age Opt Cksum Len Extern 10.255.255.172 192.255.197.249 0x80000002 2735 0x2 0x7d5a 36 user@CE3> show route 10.255.255.172 detail inet.0: 31 destinations, 32 routes (30 active, 0 holddown, 1 hidden) 10.255.255.172/32 (1 entry, 1 announced) *OSPF Preference: 150 Next hop: via t3-0/0/0.0, selected State: <Active Int Ext> Local AS: 69 Age: 47:23 Metric: 2 Tag: 12 Task: OSPF Announcement bits (1): 0-KRT AS path: I