Windows session through IOS-NAT breaks

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Mar 26th, 2008
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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 ?

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irisrios Tue, 04/01/2008 - 06:15
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This mostly happens to be an issue with MTU. Try to adjust the MTU size on the network and check if this works.

mgerstl Tue, 04/01/2008 - 06:28
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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 Tue, 04/01/2008 - 07:09
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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 Mon, 07/21/2008 - 08:33
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After a restart of the windows-servers the phenomenon did not appear anymore....


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