ICMP Blocking Woes

Mon Sep 29 20:41:17 UTC 2003

> From: "Eric Germann" <ekgermann at cctec.com>
> Date: Mon, 29 Sep 2003 15:56:04 -0400
> Sender: owner-nanog at merit.edu
> 
> 
> winders does use udp instead of icmp in their tracert program, IIRC (or at
> least they used to).  At the risk of getting my head blown off, could we say
> that was foresight :)

You have it backwards. Windows tracert uses ICMP while most Unix boxes
use the LBNL traceroute program (or something derived from it) which
uses UDP. But both rely on the return of ICMP TTL expired or
unreachable messages and blocking all ICMP breaks both.
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634