[18288] in North American Network Operators' Group
Re: MTU problems with GRE tunnels (fwd)
daemon@ATHENA.MIT.EDU (Jens Schweikhardt)
Thu Jul 9 11:21:36 1998
From: Jens Schweikhardt <schweikh@noc.dfn.de>
To: thalerd@eecs.umich.edu (Dave Thaler)
Date: Wed, 8 Jul 1998 09:36:33 +0200 (MET DST)
Cc: dennis@juniper.net, schweikh@noc.dfn.de, bridge@ip-plus.net,
horke@regio.net, nanog@merit.edu, noc@noc.dfn.de
In-Reply-To: <199807072108.RAA24092@dip.eecs.umich.edu> from "Dave Thaler" at Jul 7, 98 05:08:36 pm
Dave & Dennis,
thanks a lot for your valuable insights. And of course,
apologies for making the cisco guys look like they didn't read
the RFC. Thank God this was written as a question with a smiley...
# 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.
Ugh! The platform in question is Solaris 2.5.1. So we have one more
datapoint. I'd consider this a bug unless it's documented somewhere
outside of the kernel sources. What do you think? Should I harass
the Solaris developers?
# 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
Regards,
--
Jens Schweikhardt http://www.shuttle.de/schweikh/
SIGSIG -- signature too long (core dumped)
