BGP Next hop !

illusion_rox · ‎06-05-2008

hi all, suppose i have 3 routers RA, RB, RC connected to each other like this

RA --> RB --> RC

100 200 300

now when RB propagates any prefixes recieved from RA to RC it modifies the next hop to itself right ? is there any way to retain the ip address of RA when RB advertises to RC, kindly tell me if there is any specific bgp command for this, i tried neighbour next-hop-unchanged but it worked only from ibgp to ebgp peer.

Thanks

bineshpsm · ‎06-05-2008

you can set a route-map and specify the next hop that u require.

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neighbor route-map NEXT_HOP out

route-map NEXT_HOP

set next-hop

illusion_rox · ‎06-07-2008

thanks for the feedback, but i knew this method, i am looking for a particular bgp command for this

francisco_1 · ‎06-07-2008

How are the routers connected? Is router C on same subnet as router A?. If the receiving router C is on the same subnet, the next hop remains the same. Make sure on router B the next "neighbor ****(router b ip) next-hop-self" command is not enable.

riftjameel · ‎06-08-2008

BGP theory says that IBGP peers doesn't change the next hop ip address only EBGP peers change the next hop ip address.

I hope confederation fixes ur problem

foxbatreco · ‎06-08-2008

the default behaviour would be to advertise the NH as the ebgp peer only, in this case RA.But you can force RC to use NH as RB by using the next-hop-self option with the neighbor command & this works within iBGP only.

Rate if this helps!!!