RIR filtering & Level3
pstewart at nexicomgroup.net
Thu Nov 15 02:52:05 UTC 2007
We're getting 231740 routes from Level(3) at this moment.... hit me
offline with some specific prefixes and I'd be happy to share what we
Senior Network Administrator
5 King St. E., Millbrook, ON, LOA 1GO
Nexicom - Connected. Naturally.
From: owner-nanog at merit.edu [mailto:owner-nanog at merit.edu] On Behalf Of
Sent: Wednesday, November 14, 2007 9:43 PM
To: nanog at merit.edu
Subject: RIR filtering & Level3
Are any other L3 customers seeing the large number of /25 and smaller
routes from L3? I'm seeing almost 2500 of these routes in 4/8, some but
not as many in 8/8 and still more in L3's non-US allocations. Looking
at the AS paths for a handful of those specific networks I only see them
via our L3 connection and not via our other 2 upstreams. I'm seeing
paths to the larger aggregate networks via our other upstreams of
course; the Oregon and AT&T route servers see the same aggregates too.
To be more accurate we actually touch L3's acquisition form a year or so
ago, Telcove (19094). All of the small routes are originating from L3
Best I can tell L3 is aggregating before it advertises to a peer but not
before it advertises to a customer. Or, on the otherhand, perhaps L3 is
advertising without aggregation to Telcove and Telcove is not
aggregating before advertising to us.
So, that said, what is everyone else doing to perform sanity checks on
their learned routes? Are a good many implementing RIR filtering and
dropping everything smaller than a /24? L3 of course isn't the only
source of these tiny routes but it's so obvious I saw it and wasn't even
looking for it. This would explain why I'm getting so many more routes
from L3 too. I'm getting 232k from AT&T, 233.5k from Cox and 244k from
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