Re: Policy routing

From: Scott Whyte (swhyte@cisco.com)
Date: Sun Oct 15 2000 - 21:03:27 EDT


On Fri, 13 Oct 2000, Mark Milhollan - Franklin Employee wrote:

> Yet you can redistribute static routes into an IGP. (Not that I'm
> saying it's a good thing, usually, just that it can be done.)

Which makes sense when you consider that static routing is an IGP itself
in the sense that I can have an entire network running on only static
routes. So if my policy is simply an alternative destination-based
next-hop via a static route, I *can* get that into an IGP. But any policy
NOT destination-based (what PBR can get you) I *cannot*. Point noted.

I'd say redistributing static routes into an IGP for the purpose of
advertising a policy throughout a network is not a good thing because it's
difficult to determine what effect this propagation will have in complex
reconvergence situations. Oscillations, permanent loops, and black-holing
all come to mind, depending on the IGP(s) redistributed into.
Redistributing static routes just to advertise reachability of external
networks is complicated enough!

-Scott



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