North American Network Operators Group

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RIR filtering & Level3

  • From: Justin Shore
  • Date: Wed Nov 14 21:44:41 2007

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 L3.