nanog mailing list archives

Re: comcast routing issue question


From: Jordan Hazen <jnh () aug com>
Date: Thu, 30 Nov 2006 01:23:41 -0500


On Thu, Nov 30, 2006 at 12:28:30AM -0500, Jim Popovitch wrote:

On Thu, 2006-11-30 at 00:06 -0500, Jim Popovitch wrote:
Question:  What could cause the first trace below to succeed, but the
second trace to fail?

[snip]
Taking the 69.61.40.33/28 subnet a bit further, .36 drops at 68.86.84.70
but .37 - .39 make it.  .40 drops at 68.86.84.70, but .41 makes it.

Crazy.

Btw, the problem has now been resolved, however I'm still curious as to
what scenario could have caused that.

Perhaps CEF-style load balancing over multiple paths, with one of them
down and not properly failing over?  Per-flow balancing would decide
which path to use based on source & target IP.

-Jim P.


-- 
Jordan.


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