BCP38 making it work, solving problems

Niels Bakker niels=nanog at bakker.net
Tue Oct 12 08:49:13 UTC 2004

* christopher.morrow at mci.com (Christopher L. Morrow) [Tue 12 Oct 2004, 05:18 CEST]:
> a common occurance we've seen is a customer of a customer NOT
> announcing , nor planning on announcing, their routes to their
> upstream#1 which they use ONLY for outbound traffic (cheap transit for
> instance, and perhaps only for some portions of their total sources)
> though they announce to upstreams#2-N the proper sources to gather the
> return traffic. These things make uRPF 'difficult'.

You could use uRPF-loose there, or the customer could do:

route-map outbound-only permit 10
 match prefix-list myprefixes
 set community no-export

And bash the people who, in this age, don't have "neighbor x.y.z.a
send-community" on all their BGP sessions.

	-- Niels (who recently had a CCIE claim that he was "not aware
		  of a single ISP accepting communities from its peers"
		  - well, my experience begs to differ, with his
		  employer a rare and lonely exception to the rule) 

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