Discard Routes and Avoiding Routing LoopsRick GrazianiCabrillo College

Scenario172.16.5.0/24

Situation NormalRouterA#show ip route

172.16.0.0/24 is subnetted, 3 subnetsC 172.16.1.0 is directly connected, Ethernet0C 172.16.2.0 is directly connected, Ethernet1R 172.16.3.0 [120/1] via 172.16.2.1, 00:00:20, Ethernet1R 172.16.4.0 [120/2] via 172.16.2.1, 00:00:20, Ethernet1S* 0.0.0.0/0 is directly connected, Serial1

Link DownX

Link DownRouterA#show ip route

172.16.0.0/24 is subnetted, 3 subnetsC 172.16.1.0 is directly connected, Ethernet0C 172.16.2.0 is directly connected, Ethernet1S* 0.0.0.0/0 is directly connected, Serial1X

Link down Solution #1: no ip classlessRouterA#show ip route

172.16.0.0/24 is subnetted, 3 subnetsC 172.16.1.0 is directly connected, Ethernet0C 172.16.2.0 is directly connected, Ethernet1S* 0.0.0.0/0 is directly connected, Serial1X

Link down Solution #2: Discard RouteRTA(config)# ip route 172.16.0.0 255.255.0.0 null0X

Link down Solution #2: Discard RouteRTA(config)# ip route 172.16.0.0 255.255.0.0 null0XRouterA#show ip route

172.16.0.0/16 is subnetted, 3 subnets, 2 masksS 172.16.0.0/16 is directly connected, Null0C 172.16.1.0/24 is directly connected, Ethernet0C 172.16.2.0/24 is directly connected, Ethernet1S* 0.0.0.0/0 is directly connected, Serial1

Link down Solution #2: Discard RouteWhen all links are upRouterA#show ip route

172.16.0.0/16 is subnetted, 3 subnets, 2 masksS 172.16.0.0/16 is directly connected, Null0C 172.16.1.0/24 is directly connected, Ethernet0C 172.16.2.0/24 is directly connected, Ethernet1S* 0.0.0.0/0 is directly connected, Serial1RouterA#show ip route

172.16.0.0/16 is subnetted, 5 subnets, 2 masksS 172.16.0.0/16 is directly connected, Null0C 172.16.1.0/24 is directly connected, Ethernet0C 172.16.2.0/24 is directly connected, Ethernet1R 172.16.3.0/24 [120/1] via 172.16.2.1, 00:00:20, Ethernet1R 172.16.4.0/24 [120/2] via 172.16.2.1, 00:00:20, Ethernet1S* 0.0.0.0/0 is directly connected, Serial1

Discard Routes and Avoiding Routing LoopsRick GrazianiCabrillo College