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Date: Thu, 13 Aug 1998 20:16:20 -0400 (EDT)
From: "Joe \"Marcus\" Clarke" <marcus@miami.edu>
Subject: Re: Traceroutes to Cisco Routers
In-reply-to: <199808132339.QAA29004@stennis.ca.sandia.gov>
To: "Bruce A. Mah" <bmah@CA.Sandia.GOV>
Cc: Jeremy Shaffner <jer@jorsm.com>, freebsd-questions@FreeBSD.ORG
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Like I stated before, Cisco traceroute also uses UDP packets to
arbitrarily high ports.

Joe Clarke

On Thu, 13 Aug 1998, Bruce A. Mah wrote:

> If memory serves me right, Jeremy Shaffner wrote:
> > On Thu, 13 Aug 1998, Joe "Marcus" Clarke wrote:
> 
> > > Cisco throttles ICMP unreachables so that only 2 unreachables per second
> > > are sent.  The result puts a star in one of the fields:
> > > 
> > > i.e. (200 ms) (200 ms) *
> 
> Whew, I guessed right!  :-)
> 
> > Fair enough.  But it's dropping the second and not the third.  
> > 
> > And it doesn't explain why non-Unix OS's trace to it fine.
> 
> I can't speak for MacOS, but the Win95 tracert command uses ICMP echo requests 
> (just confirmed via tcpdump), while all of the UNIX traceroute programs use 
> UDP packets to arbitrary, high-numbered UDP ports.  Presumably the Cisco IOS 
> doesn't rate-limit ICMP echo replies in the same way that it does ICMP echo 
> requests.
> 
> (In an earlier message, you asked if the UNIX traceroutes all shared a common 
> code base, and AFAIK the answer is "yes".)
> 
> Bruce.
> 
> 
> 


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