Help with failover to 2 default routes

[davistw]

`I am having a problem with redundat default links in the below topology.

The router sare configured as below.

3845 Routers

Router 1 (Left)

router ospf 666

log-adjacency-changes

network 192.168.0.0 0.0.0.3 area 0

network 192.168.3.0 0.0.0.3 area 0

network 192.168.100.0 0.0.0.255 area 0

default-information originate metric 10

!

ip forward-protocol nd

ip route 0.0.0.0 0.0.0.0 192.168.100.2 10

! Note this is plugged into Gi0/0 of the router

Router 2 (Right)

router ospf 666

log-adjacency-changes

network 192.168.1.0 0.0.0.3 area 0

network 192.168.2.0 0.0.0.3 area 0

network 192.168.200.0 0.0.0.255 area 0

default-information originate metric 20

!

ip forward-protocol nd

ip route 0.0.0.0 0.0.0.0 192.168.200.2 20

! Note this is plugged into G0/0 of the router

I cant get the routing to work. When outbound interfaces are up each router takes it own default route. When one interface is down it doesnt work right either because it keeps its default route in its routing table and routes out to a black hole.

What am I doing wrong?

[Mitchell Dyer]

Please post "sh ip route" from both routers.

Sent from Cisco Technical Support iPhone App

[davistw]

Thanks...

Here is router 2

R2#sh 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 192.168.200.2 to network 0.0.0.0

     192.168.210.0/30 is subnetted, 1 subnets

O       192.168.210.0 [110/11] via 192.168.2.2, 00:01:45, FastEthernet0/0

     192.168.110.0/30 is subnetted, 1 subnets

O       192.168.110.0 [110/2] via 192.168.1.2, 00:01:45, FastEthernet0/1

C    192.168.200.0/24 is directly connected, FastEthernet1/0

     192.168.4.0/30 is subnetted, 1 subnets

O       192.168.4.0 [110/11] via 192.168.1.2, 00:01:45, FastEthernet0/1

     192.168.0.0/30 is subnetted, 1 subnets

O       192.168.0.0 [110/11] via 192.168.1.2, 00:01:47, FastEthernet0/1

     192.168.1.0/30 is subnetted, 1 subnets

C       192.168.1.0 is directly connected, FastEthernet0/1

     192.168.2.0/30 is subnetted, 1 subnets

C       192.168.2.0 is directly connected, FastEthernet0/0

O    192.168.100.0/24 [110/12] via 192.168.2.2, 00:01:49, FastEthernet0/0

                      [110/12] via 192.168.1.2, 00:01:49, FastEthernet0/1

     192.168.3.0/30 is subnetted, 1 subnets

O       192.168.3.0 [110/11] via 192.168.2.2, 00:01:49, FastEthernet0/0

S*   0.0.0.0/0 [20/0] via 192.168.200.2

Here is router 1

R1#sh 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 192.168.100.2 to network 0.0.0.0

     192.168.210.0/30 is subnetted, 1 subnets

O       192.168.210.0 [110/2] via 192.168.3.2, 00:04:17, FastEthernet0/1

     192.168.110.0/30 is subnetted, 1 subnets

O       192.168.110.0 [110/11] via 192.168.0.2, 00:04:17, FastEthernet0/0

O    192.168.200.0/24 [110/12] via 192.168.3.2, 00:04:17, FastEthernet0/1

                      [110/12] via 192.168.0.2, 00:04:17, FastEthernet0/0

     192.168.4.0/30 is subnetted, 1 subnets

O       192.168.4.0 [110/11] via 192.168.3.2, 00:04:17, FastEthernet0/1

     192.168.0.0/30 is subnetted, 1 subnets

C       192.168.0.0 is directly connected, FastEthernet0/0

     192.168.1.0/30 is subnetted, 1 subnets

O       192.168.1.0 [110/11] via 192.168.0.2, 00:04:18, FastEthernet0/0

     192.168.2.0/30 is subnetted, 1 subnets

O       192.168.2.0 [110/11] via 192.168.3.2, 00:04:21, FastEthernet0/1

C    192.168.100.0/24 is directly connected, FastEthernet2/0

     192.168.3.0/30 is subnetted, 1 subnets

C       192.168.3.0 is directly connected, FastEthernet0/1

S*   0.0.0.0/0 [10/0] via 192.168.100.2

R1#

It seems the static routes are overiding the injected default route.

[Mitchell Dyer · Accepted solution]

Set the metric for the default route on router 1 and 2 to 210 and 220 respectively.

Only one default route will make it to the routing table, the injected route has a higher AD than the static route, so the static route is what is used.

You can see the AD of the injected route by removing the static route from one of the routers, clearing the its OSPF neighbor and displaying the routing table again.

HTH

Sent from Cisco Technical Support iPhone App

[davistw]

Thanks Mitchell that works like a champ... If you have a minute could you teach me jedi....

This seems to work backwards from my thinking.

Why giving the routes a higher metric than 10 and 20 does it work?

Do I still need to weight the default-information originate commands?

If I take the interface for R1 down, the route swings to R2 but when R1 comes back it doesnt swing back. Why? The route is lower so shouldnt it swing back?

Give a man a fish and he will eat for one day...Teach a man to fish and he will eat for a lifetime....

[cadet alain]

Hi,

R2 gets a OE2 default route with metric 10 going to R1( with AD of 110) and it has a static default route with an AD of 1

R1 gets a OE2 default route with a metric 20 going to R2( with AD of 110) and it has a static default route with an AD of 1

Each router inserts the static default route  in the RIB because it has lower AD than the OSPF default route.

If you set the static route with higher AD than OSPF then it will use the one from OSPF. But I suppose you want to influence the exit point used by  R4 and R5 ? In this case what you  could do is use a route-map with IP sla for conditional

default route injection still using the different metrics but not used any static default route on either router.

Regards.

Alain

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[davistw]

Ahh... Light goes on....

Thanks a bunch.

I understand it now....