On 03/06/11 11:30, Sam Wilson wrote:
> We've tripped over an oddity in our routing set up and I'm baffled. I
> hope this is a suitable list to ask for assistance on.
>
> We use BGP on our metropolitan network with private ASs. At the core
> are two Cat 6500s running 12.2(33)SXI1. They run IBGP between them with
> no sync and, obviously, no IGP on a dedicated point-to-point 2x10GE
You say "obviously no IGP" but in my experience iBGP is almost always
accompanied by an IGP. Can you expand on this?
> What seems to happen is that each router advertises itself as the next
> hop for prefixes in the IBGP. Each router has a connected route for the
Again, not a common config in my experience; iBGP routers do not
normally alter the next-hop, and usually let the IGP resolve it.
> /126 between them and a local /128 for its own interface address. Each
> router then installs an IBGP route for the /128 of its neighbour routed
> via that same address. That presumably overrides the /126 of the
Where is this /128 IPv6 route coming from? IOS boxes will list Connected
and Local routes for a /126:
C 2001:630:0:9001::198/126 [0/0]
via Vlan3709, directly connected
L 2001:630:0:9001::19A/128 [0/0]
via Vlan3709, receive
...but I would not normally expect them to advertise the Local route.
Certainly our 6500s (12.2(33)SXI5) are not.
Can you send:
sh run part router bgp
sh run int <the p2p>
Cheers,
Phil
