From: Michael Davis (miked@xxxxxxxxxx)
Date: Fri Feb 15 2002 - 15:22:23 GMT-3
Great thread James. I like questions that challenge assumptions. What is
it they say about assumptions?!
Howard, I think, as you said before, we won't know definititively how IOS
does this without a thorough review of souce code. Though I'm sure Cisco
won't be sharing those details with us. ;-) I've just tried to describe,
from a pragmatic standpoint, the behavior I've experienced.
Your mileage may vary!
----- Original Message -----
From: "Howard C. Berkowitz" <hcb@gettcomm.com>
To: <ccielab@groupstudy.com>
Sent: Friday, February 15, 2002 12:22 PM
Subject: RE: How route redistribution EXACTLY works --- need confirmation
> >Mike:
> >
> >I like the condition you added, which is "routes eligible for the RIB". I
> >think, you mean another routing source, which has lower adminstrative
> >distance, didn't inject the same route into routing table.
> >
> >For ospf, when you say the routing bit set, do you mean the routes
resulted
> >from SPF, and also in the RIB? In other words, any route which does not
> >exist in the routing table will not be redistributed?
>
> That is definitely the case for BGP; it's part of loop prevention.
> BGP will also not announce a route that has a next hop that cannot be
> resolved in the RIB.
>
> I don't know definitively if that's done in Cisco's IGPs, but, in
> general, it is a basic principle of avoiding loops.
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