[18285] in North American Network Operators' Group
Re: MTU problems with GRE tunnels (fwd)
daemon@ATHENA.MIT.EDU (Dave Thaler)
Thu Jul 9 10:56:31 1998
From: Dave Thaler <thalerd@eecs.umich.edu>
To: dennis@juniper.net (Dennis Ferguson)
Date: Tue, 7 Jul 1998 17:08:36 -0400 (EDT)
Cc: schweikh@noc.dfn.de, bridge@ip-plus.net, horke@regio.net, nanog@merit.edu,
noc@noc.dfn.de
In-Reply-To: <199807071925.MAA10593@skank.juniper.net> from "Dennis Ferguson" at Jul 7, 98 12:25:09 pm
Dennis Ferguson
> I can tell you for sure that the Cisco routers do send the packets (GRE
> or IP protocol 4) with a length which includes the IP header, just like
> the RFC. If you look I think you'll find that it is your kernel which is
> subtracting out the IP header length before it hands the packet to you on
> the raw socket.
BSD Unix converts the length to host order and subtracts the IP header
length.
Linux leaves the length in net order (don't know about subtracting).
Windows leaves the length in net order and does not subtract the IP
header length.
-Dave
