Tuesday, February 21, 2012

BGP and IGP next hop alignment

When overlaying BGP onto an IGP topology you need to mindful that the next hop addresses align with the igp routing of those next hops. If there are differences then routing loops may occur.


Type escape sequence to abort.
Tracing the route to

  1 16 msec 16 msec 20 msec
  2 !H  *  !H

before changing next hop

router bgp 4
 no synchronization
 bgp log-neighbor-changes
 neighbor remote-as 44
 neighbor ebgp-multihop 10
 neighbor update-source Loopback0
 neighbor soft-reconfiguration inbound
 neighbor route-map SETLP in
 neighbor route-map SETMED out
 neighbor remote-as 4
 neighbor update-source Loopback0
 neighbor next-hop-self
 neighbor soft-reconfiguration inbound
 neighbor route-map nh1 in
 no auto-summary

route-map nh1 permit 10
 set ip next-hop

Need this because

R5#s ip route | inc
D EX [170/26140160] via, 07:08:35, Serial0/0

No comments: