You should insists on checking the server client to make sure it confirms 
to TCP standards, check and make sure if there is no static routes, entries 
added to the clients or in router, redirect in firewall etc.
How about multiple NIC on the host  ?
There may be a way to quiry Networker resorce db to find out where and how 
the reverse lookup is associated especially if it's not in DNS and host 
file on the server itself ?

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