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Re: Single IP routing problems through Level3


From: Matthew Kaufman <matthew () eeph com>
Date: Sun, 15 Jun 2008 15:07:21 -0700

Matt Palmer wrote:
A multiple-link bundle which is load balanced by source/destination pair
with an undetected dud link?  I hadn't thought of that, but it does make an
*awful* lot of sense....

I've also seen interesting OSPF misconfigurations that resulted in a router doing path-wise load balancing between the live link and an unroutable destination address that went into the bit bucket.

On the Cisco boxes I was using at the time, the hallmark of load-balancing into a dead path was that every other IP address worked, but then every some number of addresses (12, as I remember, but I'm not 100% sure) the polarity flipped, so that whichever of odd vs even had worked before was now the one that didn't for the next N addresses. Artifact of the hash algorithm in use, no doubt.

Matthew Kaufman
matthew () eeph com
http://www.matthew.at





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