North American Network Operators Group

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RE: RIR filtering & Level3

  • From: Paul Stewart
  • Date: Wed Nov 14 21:55:00 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

Paul Stewart
Senior Network Administrator
5 King St. E., Millbrook, ON, LOA 1GO
Phone: 705-932-4127
Nexicom - Connected. Naturally.

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
Justin Shore
Sent: Wednesday, November 14, 2007 9:43 PM
To: [email protected]
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
though (3356).

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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