ICMP Blocking Woes

From: "Eric Germann" <ekgermann@cctec.com>
Date: Mon, 29 Sep 2003 15:56:04 -0400
Sender: owner-nanog@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 :slight_smile:

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.