[Openswan Users] MTU Problem on LAN <-> LAN Tunnel

[dt at LF.net]

Hi,

I have a strange problem I don't really understand and I need some
help to fix it. I'm using a LAN <-> LAN Tunnel makeing a VPN
connection between the network 192.168.0.0/24 and 192.168.13.0/24. 
The 192.168.0.0/24 site uses a 2.6.8 Kernel with U2.2.0/K2.6.8masq-patch 
from debian sarge. The other site is a Redhat 9 using Superfreeswan 1.99.8. 
Everything works fine until I try to transfer big files using samba from 
192.168.13.50 to 192.168.0.1. The transfer freezes and I see the following 
fragment requests on the 192.168.0.0/24 machine:

15:31:01.418942 IP <ext-gw-ip> > 192.168.13.50: icmp 556:
192.168.0.1 unreachable - need to frag (mtu 1500)
15:31:09.419100 IP <ext-gw-ip> > 192.168.13.50: icmp 556:
192.168.0.1 unreachable - need to frag (mtu 1500)
15:31:25.420608 IP <ext-gw-ip> > 192.168.13.50: icmp 556:
192.168.0.1 unreachable - need to frag (mtu 1500)

Of course it never reaches the remote site, because the target IP
192.168.13.50 is not reachable via the Internet. If I lower the MTU
Size @192.168.13.50 erverything works fine. But I'd like to avoid
changing the MTU by hand. Is there any chance to fix this? 

Please CC: to my address because I'm not on the lists, yet.

regards

   Daniel


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