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routing question regarding rip and ospf.

syjeon
Level 1
Level 1

hi team.

I would like to know as following item which has some concern for our network.

1. if RIP has a default-route and we redistribute RIP to EIGRP, the default-route is removed as default. Right?

     --> when We test this item with Dynamips, the default-route did not redistribute to EIGRP regardless RIP has a default route.

2. if we want to redisrtibute default-route only from EIGRP to RIP, we did as following.

     ip route 0.0.0.0 0.0.0.0 tag 100

     route-map default-route-only 10

      match tag 100

     router rip

      redistribute eigrp 2000 route-map default-route-only

I would like to check to go this change.

if you have any good idea, any suggestion will be ok.

thank you.

1 Reply 1

Peter Paluch
Cisco Employee
Cisco Employee

Hello,

1. if RIP has a default-route and we redistribute RIP to EIGRP, the default-route is removed as default. Right?

    --> when We test this item with Dynamips, the default-route did not redistribute to EIGRP regardless RIP has a default route.

I cannot confirm this. If a default route is learned via RIP, and RIP is redistributed into EIGRP, the default route is redistributed into EIGRP just like any other RIP-learned route. Have you properly configured the seed metric when redistributing from RIP to EIGRP? Is the default route learned via RIP in the first place, i.e., is it marked as R in the routing table at all?

Also consider this output from my testing topology (R2 is directly connected to R3, R2 runs both RIP and EIGRP, R3 runs EIGRP):

R2(config-router)#do show ip route
Codes: C - connected, S - static, 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
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is 10.0.12.1 to network 0.0.0.0

     10.0.0.0/24 is subnetted, 2 subnets
C       10.0.12.0 is directly connected, Serial1/0
C       10.0.23.0 is directly connected, Serial1/1
R    192.0.2.0/24 [120/1] via 10.0.12.1, 00:00:04, Serial1/0
R*   0.0.0.0/0 [120/1] via 10.0.12.1, 00:00:04, Serial1/0
R2(config-router)#do show run | sec router eigrp
router eigrp 1
redistribute rip metric 100000 1 255 1 1500
network 10.0.23.2 0.0.0.0
no auto-summary
R2(config-router)#

R3(config-router)#do show ip route
Codes: C - connected, S - static, 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
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is 10.0.23.2 to network 0.0.0.0

     10.0.0.0/24 is subnetted, 2 subnets
D EX    10.0.12.0 [170/2170112] via 10.0.23.2, 00:03:15, Serial1/1
C       10.0.23.0 is directly connected, Serial1/1
D EX 192.0.2.0/24 [170/2170112] via 10.0.23.2, 00:03:15, Serial1/1
D*EX 0.0.0.0/0 [170/2170112] via 10.0.23.2, 00:03:15, Serial1/1
R3(config-router)#do show run | sec router eigrp
router eigrp 1
network 10.0.0.0
no auto-summary
R3(config-router)#

The default route is nicely redistributed from RIP to EIGRP.

2. if we want to redisrtibute default-route only from EIGRP to RIP, we did as following.

     ip route 0.0.0.0 0.0.0.0 tag 100

     route-map default-route-only 10

      match tag 100

     router rip

      redistribute eigrp 2000 route-map default-route-only

This is not correct - by configuring ip route 0.0.0.0 0.0.0.0 tag 100, you are defining a static route. If you want to inject it into RIP, you have to redistribute static into RIP, not EIGRP. If you wanted to redistribute only the default route from EIGRP to RIP, the configuration would be different:

ip prefix-list PL_EIGRP_to_RIP permit 0.0.0.0/0

route-map RM_EIGRP_to_RIP permit 10

match ip address prefix PL_EIGRP_to_RIP

set metric 1

router rip

redistribute eigrp 2000 route-map RM_EIGRP_to_RIP

Note that the default route must first be learned by EIGRP (i.e. appear in the routing table as D or DEX route), only then it may be redistributed from EIGRP to RIP.

Also note that in order to generate a default route in RIP, there is a command to do it immediately - the default-information originate command used in the  router rip context.

Best regards,

Peter

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