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Cisco OSPF Route Redistribution

Configuration Example 10: Controlling Route Redistribution Based on Tag Values

In Figure 14-4, Router B is learning six routes via EIGRP. The EIGRP routes are redistributed into OSPF with the classful routes assigned a tag of 2 and the classless routes a tag of 1. Router A is redistributing the OSPF external routes into RIP-2. The policy is to redistribute only the classless routes into RIP-2. This can be accomplished using a route map and an IP access list. Because the external routes have been tagged, a route map can be used that redistributes only routes with a tag value equal to 1. Configure the routers as shown in the listing that follows the figure. Initially, all OSPF routes will be redistributed into RIP-2 on Router A.

Figure 14-4Figure 14-4 A Route Map Can Be Used to Control Route Redistribution Based on the Tag Value

Router A
interface Loopback0
 ip address 1.1.1.1 255.255.255.255
!
interface Serial0/0
 bandwidth 64
 ip address 10.1.1.9 255.255.255.252
 no ip mroute-cache
!
interface Serial0/1
 bandwidth 64
 ip address 10.1.1.1 255.255.255.252
 clockrate 64000
!
router ospf 1
 network 10.1.1.0 0.0.0.3 area 0
!
router rip
 version 2
 redistribute ospf 1 metric 1
 passive-interface Serial0/1
 network 10.0.0.0
 no auto-summary
Router B
interface Loopback0
 ip address 2.2.2.2 255.255.255.255
!
interface Serial0
 bandwidth 64
 ip address 10.1.1.2 255.255.255.252
 no ip directed-broadcast
!
interface Serial1
 bandwidth 64
 ip address 10.1.1.5 255.255.255.252
 clockrate 64000
!
!
router eigrp 1
 network 10.0.0.0
!
router ospf 1
 redistribute eigrp 1 subnets route-map set-tags
 network 10.1.1.0 0.0.0.3 area 0
!
access-list 1 permit 6.0.0.0 0.15.255.255
access-list 1 permit 146.6.0.0 0.0.15.255
access-list 1 permit 206.6.6.0 0.0.0.15
access-list 1 permit 10.1.1.4 0.0.0.3
route-map set-tags permit 10
 match ip address 1
 set tag 1
!
route-map set-tags permit 20
 set tag 2
Router C
interface Loopback0
 ip address 3.3.3.3 255.255.255.255
!
interface Loopback1
 ip address 5.5.5.5 255.0.0.0
!
interface Loopback2
 ip address 6.6.6.6 255.240.0.0
!
interface Loopback3
 ip address 145.5.5.5 255.255.0.0
!
interface Loopback4
 ip address 146.6.6.6 255.255.240.0
!
interface Loopback5
 ip address 205.5.5.5 255.255.255.0
!
interface Loopback6
 ip address 206.6.6.6 255.255.255.240
!
interface Serial0
 bandwidth 64
 ip address 10.1.1.6 255.255.255.252
 no ip directed-broadcast
!
router eigrp 1
 network 5.0.0.0
 network 6.0.0.0
 network 10.0.0.0
 network 145.5.0.0
 network 146.6.0.0
 network 205.5.5.0
 network 206.6.6.0
 no auto-summary

Router D
interface Serial0/1
 ip address 10.1.1.10 255.255.255.252
 clockrate 64000
!
router rip
 version 2
 network 10.0.0.0

Verify that Router D is receiving the redistributed OSPF routes from Router A.

rtrD#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
    D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
    N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
    E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
    i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default
    U - per-user static route, o - ODR
Gateway of last resort is not set
R  205.5.5.0/24 [120/1] via 10.1.1.9, 00:00:01, Serial0/1
   206.6.6.0/28 is subnetted, 1 subnets
R    206.6.6.0 [120/1] via 10.1.1.9, 00:00:02, Serial0/1
R  5.0.0.0/8 [120/1] via 10.1.1.9, 00:00:02, Serial0/1
   6.0.0.0/12 is subnetted, 1 subnets
R    6.0.0.0 [120/1] via 10.1.1.9, 00:00:02, Serial0/1
   172.16.0.0/24 is subnetted, 1 subnets
R    172.16.1.0 [120/1] via 10.1.1.9, 00:00:02, Serial0/1
R  145.5.0.0/16 [120/1] via 10.1.1.9, 00:00:02, Serial0/1
   10.0.0.0/30 is subnetted, 3 subnets
C    10.1.1.8 is directly connected, Serial0/1
R    10.1.1.0 [120/1] via 10.1.1.9, 00:00:02, Serial0/1
R    10.1.1.4 [120/1] via 10.1.1.9, 00:00:02, Serial0/1
   146.6.0.0/20 is subnetted, 1 subnets
R    146.6.0.0 [120/1] via 10.1.1.9, 00:00:05, Serial0/1

Modify the configuration on Router A so that only OSPF routes with a tag value of 1 get redistributed into RIP.

Router A
router rip
 version 2
 redistribute ospf 1 metric 1 route-map check-tags
 passive-interface Serial0/1
 network 10.0.0.0
 no auto-summary
!
route-map check-tags permit 10
 match tag 1

Verification

Verify that the only OSPF routes redistributed into RIP on Router A are those routes with a tag value of 1.

rtrD#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
    D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
    N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
    E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
    i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default
    U - per-user static route, o - ODR
Gateway of last resort is not set
   206.6.6.0/28 is subnetted, 1 subnets
R    206.6.6.0 [120/1] via 10.1.1.9, 00:00:01, Serial0/1
   6.0.0.0/12 is subnetted, 1 subnets
R    6.0.0.0 [120/1] via 10.1.1.9, 00:00:02, Serial0/1
   10.0.0.0/30 is subnetted, 3 subnets
C    10.1.1.8 is directly connected, Serial0/1
R    10.1.1.0 [120/1] via 10.1.1.9, 00:00:02, Serial0/1
R    10.1.1.4 [120/1] via 10.1.1.9, 00:00:02, Serial0/1
   146.6.0.0/20 is subnetted, 1 subnets
R    146.6.0.0 [120/1] via 10.1.1.9, 00:00:02, Serial0/1
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