BGP Multihop Routing?

[ahmad82pkn]

Hi,

i configured EBGP Multi hop between 2 routers which are 10 HOPS away from each other.

I can see Loopback advertised from Router A (1.1.1.1)  in Router B routing table.

Now when i try to trace route(from Router B) the Loopback advertised by Router A(1.1.1.1/32) it stops at first hop.

Does this mean i will need to add static route for destination 1.1.1.1/32 on all 10 intermediate HOPS ?? if so then what the use of this EBGP -Multi hop.

I thought once BGP neighbor is up. all routes sent from Router A into Router B routing table should be reachable ??? isnt it this way?

[Richard Burts]

Clearly if the next hop router is to forward a packet toward 1.1.1.1 then this router must have some entry in its routing table that tells it how/where to forward the packet. That entry might come from a static route, or from its participation in BGP,  or from running some other routing protocol which has an entry for 1.1.1.1.

So one of the issues to be aware of when running EBGP multi hop is that the intermediate routers must be able to forward the data traffic to the destinations advertised in EBGP.

HTH

Rick

[bava_ccna]

Yes, you need IGP routing between the ebgp peers if it's not directly conneted. By default,ebgp session can be established only if the destination is 1 hop away, this is because TTL is set to 1 in ebgp OPEN msg..So if want to establish ebgp session between routers which are not directly connected then EBGP Multihop will help. Note that ebgp multihop wont establish the bgp session if there is no igp routing between the peers..

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-bava