Categories R&S

BGP – implement and troubleshoot Peerings – Multihop eBGP Peerings


When we were implementing eBGP peering, remember that we saw that the outgoing TTL was set to 1.

So what happen if we want to establish an eBGP peering with a couple of routers between our peer ?



Establish an eBGP session between R10 and R20 loopbacks.





Configuration and verification:

So this seems to be easy, let’s just add a network statement on both R10 and R20.

R10(config)#router bgp 10
R10(config-router)#neigh remote-as 20
R10(config-router)#neigh update-source lo0

R20(config)#router bgp 20
R20(config-router)#neigh remote-as 10
R20(config-router)#neigh update-source lo0


As expected, the BGP session is not coming UP.



Let’s try to use the ebgp multi hop command.

So from R10, R20 is 5 hop away.

R10(config-router)#neighbor ebgp-multihop 5

R20(config-router)#neigh ebgp-multihop 5


And now the session is UP !

%BGP-5-ADJCHANGE: neighbor Up

R10#sh ip bgp sum
Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd      4           20      11      11       11    0    0 00:00:07        7


That’s all for this ebgp multihop command.



Thank you for reading.




BGP – implement and troubleshoot Peerings – Multihop eBGP Peerings