[ih] Exterior Gateway Protocol

[tony.li at tony.li]

>> IBGP is necessarily multi-hop, so that’s been a requirement since day 1.
> 
> Minor nitpick.  There is nothing that prevents me from using iBGP between two peers on the same link.
> 
> iBGP between loopbacks does need to be multi-hop.  But iBGP between directly connected interfaces does not need to be multi-hop.


True, but no one would run it that way.  That makes both of those interfaces into single points of failure.  If you run it between loopbacks, then any path suffices.

This was also effectively the early driver for multi-hop EBGP: pre-LAG link groups.

Tony