92 Byte ICMP Blocking Problem

Chris Adams cmadams at hiwaay.net
Fri Sep 12 17:52:58 UTC 2003


Once upon a time, Richard J.Sears <rsears at adnc.com> said:
> Since then, we have been hammered with customer complaints concerning
> the inability to talk to mail servers and ssh to their servers, as well
> as other weird network issues, all centering around the time we started
> blocking 92 Byte ICMP packets.
> 
> Has anyone else seen this, and if so, is the only resolution to stop the
> blockage of 92 Byte ICMP Packets..?

Yes.  As soon as we put the policy route map in place, we had some
people unable to talk via SSH, SMTP, or POP3.  It was random: one person
here in the office couldn't SSH to a particular server.  He could SSH to
other servers, and the rest of us could SSH to the server he could not.
We had similar experiences with SMTP and POP3.  When we took the policy
route map back out, the problems went away.

This is with IOS 12.0(25)S1 on a 7513 doing dCEF.  We put the policy
route map on the FE interface linking this router to the POP core
router; this router has MC-T3 interfaces and ethernets to Ascend TNTs
and such.  The intent was to stop the 92 byte ICMP echos from reaching
the Ascend TNTs, since several of them were rebooting constantly.

-- 
Chris Adams <cmadams at hiwaay.net>
Systems and Network Administrator - HiWAAY Internet Services
I don't speak for anybody but myself - that's enough trouble.



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