RE: [nsp] traceroute and icmp

From: Scott Morris (swm@emanon.com)
Date: Thu Nov 29 2001 - 15:43:10 EST


No. Traceroute is simply program.

Unix and Cisco IOS choose to use a UDP variant of it. Microsoft uses a
straight ICMP.

Either way, it's done by incrementing the TTL field, which would cause each
router along the way to send back ICMP TTL-Exceeded messages (per the RFC,
typical behavior).
Until the trace program finally reached it's end desination. In which case,
the unix/IOS programs would get an ICMP Port-Unreachable message back since
they sent a UDP message, and Microsoft's tracert program would receive an
ICMP Echo-Reply message back.

So trace isn't PART of ICMP, it simply USES ICMP.

Scott

-----Original Message-----
From: Tim Booth [mailto:trbooth@chartermi.net]
Sent: Thursday, November 29, 2001 3:36 PM
To: cisco-nsp@puck.nether.net
Subject: [nsp] traceroute and icmp

Hello...

   Doesn't icmp have it's own traceroute extension, just like echo and
echo reply, or is that just Cisco adding it on? I remember reading this
somewhere but I cannot verify this. Anyone know?

Kind Regards,
Tim Booth
MCDBA, CCNP, CCDP, CCIE written
-----------------------------------------
Those who would give up essential liberty to purchase a little temporary
safety deserve neither liberty nor safety.
Benjamin Franklin, 1759



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