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New Member

BGP routing through VPN topology (Hub 'n Spoke)

Hi all,

have here a Hub 'n Spoke VPN topology between three Rtrs (where RtrB is the hub site), VPN tunnels are build up between RtrB-RtrA and RtrB-RtrC, EBGP peering is the same as the VPN topology(RtrB 2 RtrA and RtrB 2 RtrC). Now my problem: BGP comes up the peers are send/receiving the routes, but a connection between RtrA-RtrC is not possible, although the routes from the private LAN A is in RtrC routing table. Is there an issue like Spilt-Horizon in VPN, may be its not possible to route traffic on the Hub site from on tunnel to the next tunnel. Many thanks in advance...

2 REPLIES
New Member

Re: BGP routing through VPN topology (Hub 'n Spoke)

I don't know if you use hup and spoke of Frame-relay and use multipoint-to-point connection, if this is the case, that means the ip addresses of your three router are in a common subnet. I think that may be a problem because that BGP treat NBMA such as FR with this behaviour: RtrA RtrB and RtrC have the same subnet ip address, and when RtrB advertise RtrA's bgp route to RtrC, the next hop is RtrA's interface address, not RtrB's, so if RtrC have no diretcly PVC to RtrA, RtrC can not ping RtrA's ip address even though they are in the same subnet. So, if this is the case, i suggest you use subinterface and p2p FR connection on RtrB to the other Routers. This is the only possible condition i ever known, maybe not your case. :-)

Re: BGP routing through VPN topology (Hub 'n Spoke)

If thats the case, a frame map statement would help in reachability of next hops. Put one map statement at A and C each....

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