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From: Nikos Vassiliadis <nvass@teledomenet.gr>
To: freebsd-net@freebsd.org
Date: Tue, 27 May 2008 16:51:38 +0300
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Cc: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net>,
	Stefan Lambrev <stefan.lambrev@moneybookers.com>
Subject: Re: Adjust Maximum Segment Size?
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On Tuesday 27 May 2008 12:37:20 Stefan Lambrev wrote:
> I'm experimenting with gre tunnels - the problem comes from async
> routes. From gre0 I receive traffic, but replies are sent over Ethernet
> card. So I can't make mtu on if0 the same as the mtu on gre0.

You could change the mtu size for certain destinations using
route(8) and the -mtu modifier. Lower the mtu for the known
destination or perhaps for the default route to keep your
system from using the interface's mtu.

Of course, this will influence mtu and not only mss...

HTH, Nikos