Re: Looking for information on IGP choices in dual-stack networks

[Randy Bush <randy () psg com>]

> > Think of scenarios where you have mergers/acquisitions where
> > different portions of the now amalgamated network were designed
> > differently and there may be too much pain or require too much time
> > to redesign rather than bolt together and redistribute.
> But in that case, don't they usually say "The heck with it" and
> continue using 2 separate ASN numbers?

we didn't take that path.  we used separated igps (did not want to share
blood with yet to be trusted acquired engineers), and bgp confederation
so there was one external asn.  

a useful transition strategy.  but in that configuration, bgp at the
confed border is ebgp, not ibgp.  this has interesting consequences on
timing of routing propagation, even with timers turned down.

see http://archive.psg.com/030226.apnic-flap.pdf

randy