I have a Cisco ASA 5510 appliance at my corporate office and cisco
1811's at our branch sites. I am troubleshooting some connectivity
issues with a new Exchange server on the network. Troubleshooting as
led me to think that the problem is a fragmentation issue on the
network. When I started looking at the router configs ( 1811 ) i
noticed that the previous network admin had set the default mss size
to 1300, however no one could tell me why this had been done. I have
heard of this being done to resolve some web browsing errors, but I
have removed the setting and no one is complaining. Since removing the
mss setting on the 1811's I can now send a test ping with don't
fragment flag and a size of 1442 from all branch sites into the
corporate router. This a substantial increase from before when the
size was being limited to 1300 or less. However going out from corp
the largest packet I can send is 1250. I have checked and rechecked
the ASA config file and can find no setting to lower the mss or mtu
size.


Anyone have any thoughts ?

Thanks