Ethereal-users: RE: [Ethereal-users] Determining MTU from sniffed packets ...

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From: "James Courtier-Dutton" <James@xxxxxxxxxxxxxxxxxxxx>
Date: Wed, 23 Jan 2002 20:02:59 -0000
This will only work if the hosts are using Path MTU discovery.

If it is sniffing on Ethernet assume MTU 1500.
Then look for "ICMP Destination Unreachable message" packets for "Next-Hop
MTU" information.

The information you need is described in RFC 1191 Path MTU Discovery,
Section 4.

An indication that Path MTU discovery is being used between two hosts, is
the Don't Fragment (DF) being set in the IP header.

Cheers
James


> -----Original Message-----
> From: ethereal-users-admin@xxxxxxxxxxxx
> [mailto:ethereal-users-admin@xxxxxxxxxxxx]On Behalf Of COLIN Stephane
> Sent: 23 January 2002 12:07
> To: ethereal-users@xxxxxxxxxxxx
> Subject: [Ethereal-users] Determining MTU from sniffed packets ...
>
>
> Hi all !
>
> Someone know how i can determining the MTU of 2 hosts with from sniffed
> packets between these 2 hosts ?
>
> Thanks ...
>
>
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