[c-nsp] Interesting iBGP problem

[Félix Izquierdo]

1 min is the default bgp scan time for next-hop reachability checking. 
It seems that the next-hop for the routes learned from border 1 is 
unreachable. You must use next-hop-self in all the ibgp sessions 
configured at the border routers.



Kevin wrote:

> I have two 7500 routers, border1 and border2, border1 currently has a
> GiGE to a backbone router, border2 will soon have an ds3 to another
> providor. I have a GIGe connection between the routers.
> Border2 has a brand new default config. Basically what I can tell is
> happening is that when I configure iBGP between the two routers, border2
> will insert all the ebgp routes from border1 into the routing table and
> then about 1min later it'll remove all the routes out of the routing
> table. Then after another minute the routes are back. Has anyone seen
> this before? I checked to see if bgp was flapping, and it was'nt. I
> checked for interface errors, their was'nt any.
> I am running 12.3(8)T3 on these routers. Below are the bgp configs.
> 
> 
> Kevin,
> 
> 
> Border1:
> router bgp 25720
>  bgp log-neighbor-changes
>  bgp bestpath compare-routerid
>  neighbor 192.168.1.2 remote-as 25720
>  neighbor 192.168.1.2 update-source Loopback0
>  neighbor 207.67.87.49 remote-as 4323
>  neighbor 207.67.87.49 description TWtelecom
>  neighbor 207.67.87.49 version 4
>  !
>  address-family ipv4
>  neighbor 192.168.1.2 activate
>  neighbor 207.67.87.49 activate
>  neighbor 207.67.87.49 next-hop-self
>  neighbor 207.67.87.49 remove-private-as
>  neighbor 207.67.87.49 soft-reconfiguration inbound
>  neighbor 207.67.87.49 distribute-list BGP_Advertisment out
>  neighbor 207.67.87.49 route-map tw-in in
>  no auto-summary
>  no synchronization
>  network 199.199.208.0 mask 255.255.248.0
>  aggregate-address 199.199.208.0 255.255.248.0 summary-only
>  exit-address-family
> 
> Border2:
> 
> router bgp 25720
>  no synchronization
>  bgp log-neighbor-changes
>  neighbor 192.168.1.1 remote-as 25720
>  neighbor 192.168.1.1 update-source Loopback0
>  no auto-summary
> 
> 
> 
> 
> 
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