Windows session through IOS-NAT breaks

[mgerstl]

We use a Cisco2851 (V12.4(3f)) to do PAT (NAT Overload).

But over more or less time the windows clients stop a tcp-session to a Win-Server showing "The handle is invalid" or "the networkname is no longer available".

This happens specialy in sessions like large-file-transfer or massive property changes in the AD.

Does anybody knows about this problem and how to fix it ?

[irisrios]

This mostly happens to be an issue with MTU. Try to adjust the MTU size on the network and check if this works.

[mgerstl]

Why should MTU be an issue?

If we would do PAT with a change in packet-length (like PPPoE or so), I would understand.

But we do PAT from an inner side of ethernet-intranet to an outer side of ethernet-intranet. Just source IP and source Port is changed (and the checksums of course), but the packet-length should stay - right?

[Danilo Dy]

Hmmm, just heard this from a friend. After changing to STATIC NAT (as an interim solution), the problem disappear.

However, they are using PIX.

Can you try changing to STATIC NAT?

[mgerstl]

After a restart of the windows-servers the phenomenon did not appear anymore....