BGP Loopback Address Multiple Providers

[caplinktech]

When establishing BGP sessions with multiple providers and iBGP sessions inside of your network, do you typically use the same loopback address for all sessions on a device or do you use a separate loopback interface for each session?

For example, if you have 3 external providers, Provider A, B, and C and you have 2 Edge peering routers that connect to these ISPs, do you use 1 loopback interface on each of your edge routers to establish all of the BGP sessions or do you use multiple?

If multiple, do you use one for each session or group them in some manner?

For this example, assume the PE of Providers A and B is connected to CE1 and PE of Provider C is connected to CE2 and CE1 and CE2 are running iBGP between them.

Thanks for any assistance you can offer.

[Richard Burts]

In my experience with BGP it is common to use Loopback interface addresses for peering with IBGP peers. This makes especially good sense when there might be more than 1 interface on the router which can transmit traffic that will reach the peer. For EBGP peers it is more common to use the address of the physical interface which connects to the EBGP peer.

HTH

Rick

[caplinktech]

Hi Richard,

Thanks.

When you setup the loopbacks for peering with your iBGP peers, do you use a single loopback for all peers or a loopback per peer?

[Richard Burts]

I use a single loopback for all peers. Perhaps there is a scenario where you might want a unique loopback per peer, but I can not think what that scenario would be.

HTH

Rick

[Pavel Bykov]

Single loopback for all iBGP peers. Only interface addresses for eBGP peers. Like Rick said.