[143775] in North American Network Operators' Group
Re: Cogent --> Google Public DNS routing issue
daemon@ATHENA.MIT.EDU (Patrick W. Gilmore)
Wed Aug 17 09:13:38 2011
From: "Patrick W. Gilmore" <patrick@ianai.net>
In-Reply-To: <CAL9jLabiLora9QdqnL_brKt9=d7g=EScCuCjspYwxgyO7CL4+Q@mail.gmail.com>
Date: Wed, 17 Aug 2011 09:13:00 -0400
To: NANOG list <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Aug 17, 2011, at 1:07 AM, Christopher Morrow wrote:
> On Wed, Aug 17, 2011 at 12:09 AM, Robert Glover <robertg@garlic.com> =
wrote:
>> Hello,
>>=20
>> We have noticed that from our Cogent link (as well as from ALL U.S. =
based
>> points we tested via the Cogent Looking Glass:
>> http://www.cogentco.com/en/network/looking-glass), traceroutes to =
8.8.8.8
>> and 8.8.5.5 all seem to go over to Europe:
>=20
> 8.8.5.5 ain't the driods you are looking for...
In the traceroute appended to the original post, he did trace to =
8.8.4.4.
While it did go all over, I don't see the problem - it got to the =
destination host.
Anycast is OK for some things, but it depends on BGP. BGP has zero =
concept of latency, loss, or geography. Expecting anycast to guarantee =
an optimal path or location is a grave error.
The possible reasons for this are nearly innumerable. Perhaps Congent =
<> Google is congested in the US so one or the other prefers EU? =
Perhaps there is some IGP metric messed up inside Cogent that prefers =
the EU? Perhaps more nefarious problems, such as Google de-peering =
Cogent in the US? Etc., etc.
You may be able to find out if you look, and you may not (I didn't even =
try). But even if you do figure out the answer, you can't fix it. Only =
Cogent and/or Google can.
Moreover, you can see things like this with anycast even when there is =
no problem!
--=20
TTFN,
patrick
