Win2003-NAT outbound connection mapping delete


Vibhor Mahajan


I have configured NAT on Win2003 server (SP2). Local address for NAT is
192.168.25.x and global interface IP address is

Client application: runs on computer inside NAT
Server application: runs on computer outside NAT

Server listens for TCP connections on port no. 1334. Client connects twice
to server using TCP.

But after a random amount of time, first TCP connection mapping is deleted
on NAT server. netstat -n command used on both client and server after
mapping is deleted shows connection in ESTABLISHED state. When server or
client closes connection then fresh mapping is again created at NAT server.

Since mapping is deleted, server and client are not able to send \ recv data
using this TCP connection. Data transfer on 2nd connection is OK.

Moreover, mapping is only deleted when client is behind NAT server and our
server is not behind NAT. If server is behind NAT and client is outside then
this problem is not coming.

Kindly suggest why NAT server is deleting the mapping and how can it be

PS: If this is not the right newsgroup for above question, kindly suggest
suitable newsgroup.

Thanks in advance.

Best Regards,

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