Hello,

1. Try enabling fragmented packets on the rules that allow outbound traffic 
from the LAN (or OP1 etc) and also tick the box in advanced options to allow 
fragmented packets.

2. If that doesn't work, try lowering the MTU of the WAN interface on both 
ends of the link.

Kris.

----- Original Message ----- 
From: "Michael Stecher" <Michael dot Stecher at cib dot de>
To: <m0n0wall at lists dot m0n0 dot ch>
Sent: Wednesday, February 13, 2008 8:51 AM
Subject: [m0n0wall] Problem with IPSec VPN Tunnel - MTU-Size?


Hello,

we've got a running IPSec tunnel betwenn two locations. Now we've got the 
problem that some packets get lost. We've changed the mtu on a client PC to 
1400 an anything works fine.

Now my question: Is it possible to change the mtu-site (or the mss-value) of 
the tunnel?

More datailed information ist described here: 
http://forum.m0n0.ch/index.php/topic,1630.0.html

Have many thanks for your help.

Best regards,

Michael Stecher