OSPF + iBGP + eBGP + 2 switches failover
November 15th, 2008
This is a rough failover for 2 switches that have 2 links to the same ISP, and they have a xconnect between both. They run OSPF sending out a default route. Switch A is the master and Switch B is the slave. If Switch A’s primary xconnect dies, switch B will announce a default route via iBGP and OSPF to keep traffic flowing to the net.
Switch A:
interface GigabitEthernet0/1 description Primary Internet Link no switchport ip address 192.168.0.118 255.255.255.252 no ip redirects no ip proxy-arp ! interface GigabitEthernet0/2 description Layer3 To Switch B no switchport ip address 192.168.1.253 255.255.255.252 no ip redirects no ip proxy-arp ip ospf cost 10 ! router ospf 10 log-adjacency-changes auto-cost reference-bandwidth 10000 process-min-time percent 10 traffic-share min across-interfaces redistribute connected metric-type 1 subnets redistribute static metric-type 1 subnets route-map REDIST-STATIC network 192.168.1.252 0.0.0.3 area 0 maximum-paths 8 default-information originate metric 10 metric-type 1 ! router bgp 12345 no synchronization no bgp fast-external-fallover bgp log-neighbor-changes network 10.10.10.0 mask 255.255.255.0 neighbor 192.168.0.117 remote-as 1111 neighbor 192.168.0.117 description Primary Internet Link neighbor 192.168.0.117 version 4 neighbor 192.168.0.117 send-community neighbor 192.168.0.117 prefix-list default in neighbor 192.168.0.117 prefix-list aggregate out neighbor 192.168.1.254 remote-as 12345 neighbor 192.168.1.254 version 4 neighbor 192.168.1.254 next-hop-self no auto-summary !
Switch B (backup xconnect)
interface GigabitEthernet0/1 description Layer3 to Switch A no switchport ip address 192.168.1.254 255.255.255.252 ip ospf cost 10 ! interface GigabitEthernet0/2 no switchport ip address 192.168.2.121 255.255.255.252 ! router ospf 10 log-adjacency-changes auto-cost reference-bandwidth 10000 traffic-share min across-interfaces redistribute connected metric-type 1 subnets network 192.168.1.252 0.0.0.3 area 0 maximum-paths 8 default-information originate metric 300 metric-type 1 ! router bgp 12345 no synchronization no bgp fast-external-fallover bgp log-neighbor-changes network 10.10.10.0 mask 255.255.255.0 neighbor 192.168.2.121 remote-as 1111 neighbor 192.168.2.121 prefix-list default in neighbor 192.168.2.121 prefix-list aggregate out neighbor 192.168.2.121 route-map backup-in in neighbor 192.168.2.121 route-map backup-out out neighbor 192.168.1.253 remote-as 12345 neighbor 192.168.1.253 version 4 neighbor 192.168.1.253 next-hop-self route-map backup-in permit 10 set local-preference 90 ! route-map backup-out permit 10 match ip address prefix-list aggregate set metric 10 ! route-map backup-out permit 20 ! ip prefix-list aggregate seq 5 permit 10.10.10.0/24
Switch B:
BGP routing table entry for 0.0.0.0/0, version 2 Paths: (2 available, best #2, table Default-IP-Routing-Table) Not advertised to any peer 1111 192.168.2.121 from 192.168.2.121 (192.168.5.142) Origin IGP, metric 0, localpref 90, valid, external 1111 192.168.1.253 from 192.168.1.253 (192.168.5.249) Origin IGP, metric 0, localpref 100, valid, internal, best