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RE: looping traceroutes
From: "Hire, Ejay" <Ejay.Hire () Broadslate net>
Date: Wed, 19 Sep 2001 11:51:35 -0400

This behavior would occur if the traffic was routed to a loopback interface.

-----Original Message-----
From: Leo Bicknell [mailto:bicknell () ufp org]
Sent: Wednesday, September 19, 2001 8:09 AM
To: nanog () merit edu
Subject: Re: looping traceroutes

On Wed, Sep 19, 2001 at 12:40:51AM -0700, Ratul Mahajan wrote:
Do you think that it can be a real persistent routing loop (data packets
would actually shuttle between the two interfaces) as against some
wierdness because of traceroute?

I'd tell you a story, but it would make all of nanog cringe.  Put
simply, I know of at least one medium size regional network who
when they couldn't make "bgp work" decided to implement a series
of scripts that logged into all routers and installed statics to
make things work.

Let me just tell you, after a few short weeks of adding and removing
(and missing) such routes there were loops all over the place, many
of which are probably still there. :-(

There are a number of ways long lived loops can occur.  I believe
others have pointed out some other methods.

Leo Bicknell - bicknell () ufp org
Systems Engineer - Internetworking Engineer - CCIE 3440
Read TMBG List - tmbg-list-request () tmbg org, www.tmbg.org

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