iBGP vs. eBGP RE: CPU Utilization

[lincwarren]

I'm curious to know if internal BGP is inherently less CPU intensive than external BGP.  That appears to be the case on our network, but I can't think of a solid reason why that would be true.  If anyone has facts/thoughts on the subject, I'd love to see them.

Thanks in Advance!

[Giuseppe Larosa]

Hello Warren,

in iBGP you can take advantage of BGP route reflectors and/or confederations to reduce the number of iBGP sessions.

Also, what counts is the number of update-groups = number of different outbound policies.

Other possible differences may be in the BGP scanner related timers and on the possible use of BGP next-hop tracking to reduce CPU usage.

The first ones can have different values (but it should per address-family and not per BGP session type iBGP vs. eBGP) and BGP next-hop tracking may fit with iBGP scenarios

Apart from this, generally speaking I have no evidence of less use of CPU in iBGP in comparison to eBGP

Hope to help

Giuseppe