RE: gre tunnel MTU adjustment

["Christian Storch" <storch@infra.net>]

Perhaps you want to say:

iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j
TCPMSS --clamp-mss-to-pmtu

?
Another simple possibility for small networks is to adjust
the default MSS of every client to something about 1400.
(that value fits for nearly every kind of tunnel)

Christian

PS: Something like a crazy workaround is to establish two tunnels and
bundle them with MPP. Finally you could get 'virtual' 1500 MSS.
Normally used for real time traffic solutions.

-----Original Message-----
From: Teun Vink [mailto:teun@moonblade.net]
Sent: Thursday, May 15, 2003 10:33 AM
To: Jeff S Wheeler
Cc: debian-isp@lists.debian.org
Subject: Re: gre tunnel MTU adjustment

...

Hi,

I use a GRE tunnel between my DSL connection at home and the network of
the ISP I work for. I use this iptables line in my setup, which fixes
the MTU for all outgoing packets:

iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp

Works just fine...

...