Subject: Re: Max nos of routes in FIB

From: Danny McPherson <[email-masked]>
Date: Sun, 22 Dec 2002 15:11:12 -0700

> As i understand we can have some 60-100K routes in the BGP table in the 
> core. I wanted an estimate as to how many of these are actually injected
> into the forwarding table? Are all these 80K+ routes actually inserted 
> into the forwarding table also?

Actually, I've seen 2+ million BGP paths (sum of all the routes in the 
Adj-RIBs-In) in the core of some large networks, with ~115-160k unique 
prefixes in the Loc-RIB (and FIB, subsequently).  The CIDR report is 
teetering around 117k unique prefixes, as of late, I believe.

Of course, with the add-paths draft it could be be more, with the 
bounded-longest-match it could be less.

Of course, you could do clever things when populating the FIB to 
reduce the size, but that's an implementation issue.  

-danny

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From: Curtis Villamizar <[email-masked]>
Date: Mon, 23 Dec 2002 10:38:52 -0500

> reduce the size, but that's an implementation issue.  

I think the question was how big does the FIB have to be and for a few
ISPs with lots of internal unaggregated routes that get aggregated on
the way out its around 2m+ paths (Adj-In entries) and around 200k
routes (FIB entries), maybe a bit more.  The number of routes in the
CIDR reports represent routes after aggregation exported to a peer.

Routers which are being designed so as not to become obsolete quickly
have to set targets quite a bit higher.

Curtis