Multiple BGP Peering to same remote as

[ashb928]

Hello,

Trying to lab up a scenario but having issues establishing BGP Peering.

We have an iBGP Peering (same ASN) between RA and RB, they both directly connected and peering is fine.

There is a router RC directly connected to RA using different ASN (eBGP) and this peering is fine as well.

I am trying to establish peering between RC and RB, both addresses are pingable but no peering between them. whats wrong here, see attached?

Your help is appreciated.

[MHM Cisco World]

In RA add static route for RC IP (IP you use in bgp) 

In RC add static route for RA IP (IP yph use in bgp)

In RA and RC use ebgp multi hop

MHM

[paul driver]

Hello
you state have reachabilty to/from either rtr so the assumption this is through some static routing or igp like ospf ?
however as the rtrs as are not directly connected and as  bgp is tcp connection orientated by default it expects directly connected peers - which could be seen if you enable a debug of bgp pertaining to that new peering - you would most probably receive a msg referencing some bgp connected failure no route to peer 

To bypass or negate thdi sanity check you can tell the bgp rtr the nexthop is more than a single next-hop (TTL1) away

There are various ways of doing this or you can disable the sanity check altogether 

example: each option is mutually exclusive to each other 
1-neighbour xxxx ebgp multihop x (default 255)
2- neighbour xxxx ttl -security hop xx 
3- neighbour xxxx  disable-connected-check

Note- if you are sourcing the peering from an interface other then its directly connected interface you will also have to specify this in the bgp stanza
neighbour xxxx update-soured (interface)

[Joseph W. Doherty]

Are you sure there's no peering, or perhaps the additional path, RC<>RB isn't being used?  (I.e. routes not shown being passed between RC<>RB?)

[supunit21]

Hi @ashb928 ,

Can you please share the config from RA/RB/RC?