From: Brian Dennis (brian@5g.net)
Date: Wed Sep 11 2002 - 17:55:48 GMT-3
The confusion seems to be in how some vendors trigger a device to send
back the ICMP time exceeded message. Cisco sends UDP packets and
Microsoft sends ICMP echos as stated earlier. It's not a great idea to
generate an ICMP message about another ICMP message and is why some
vendors chose to use UDP.
Generating an ICMP message about another ICMP message is kind of like
opening a trouble ticket about another trouble ticket ;-) But the
reasoning behind it was that some devices might actually be listening to
the same UDP port of the packet that the traceroute application is
sending to. This would cause the final ICMP port unreachable to not be
generated. Since basically all devices will reply to an echo, some
vendors implemented traceroute using ICMP echos to trigger the
responses.
btw... I'm not sure if you're agreeing with me or trying to point
something else out ;-)
Brian Dennis, CCIE #2210 (R&S/ISP Dial)
-----Original Message-----
From: MADMAN [mailto:dave@interprise.com]
Sent: Wednesday, September 11, 2002 1:16 PM
To: Brian Dennis
Cc: 'Becky Qiang'; ccielab@groupstudy.com
Subject: Re: non-ICMP ping and non-ICMP traceroute
I think that's typical. Increment the TTL by one utilizing the time
exceeded ICMP message is what traceroute does as it is itself not an
ICMP packet.
Dave
Brian Dennis wrote:
>
> Cisco's implementation of traceroute (IOS and CatOS) is not based on
> sending ICMP packets. It's based on sending UDP packets.
>
> Brian Dennis, CCIE #2210 (R&S/ISP Dial)
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Becky Qiang
> Sent: Wednesday, September 11, 2002 11:05 AM
> To: Ravi Chandran; ccielab@groupstudy.com
> Subject: Re: non-ICMP ping and non-ICMP traceroute
>
> I've heard of such thing. Both ping and traceroute command in Cisco
CLI
> are
> developed based on ICMP...Becky
>
> ----- Original Message -----
> From: "Ravi Chandran" <s_ravichandran@hotmail.com>
> To: <ccielab@groupstudy.com>
> Sent: Wednesday, September 11, 2002 9:09 AM
> Subject: non-ICMP ping and non-ICMP traceroute
>
> > Hi everyone,
> >
> > While in a telenet session on a Cisco switch, can I generate a
> non-ICMP
> > ping and non-ICMP traceroute from the command line?
> >
> >
> >
> > Thanks.
> >
> > Ravi
> >
> >
>
------------------------------------------------------------------------
> >
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-- David Madland CCIE# 2016 Sr. Network Engineer Qwest Communications 612-664-3367"You don't make the poor richer by making the rich poorer." --Winston Churchill
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