Microsoft KB Archive/248809

= PRB: DCOM Does Not Work over Network Address Translation-Based Firewall =

Article ID: 248809

Article Last Modified on 11/17/2003

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APPLIES TO

 Microsoft COM+ 2.0 Standard Edition, when used with:  Microsoft Windows 2000 Standard Edition

 Microsoft Windows NT 4.0 

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This article was previously published under Q248809



SYMPTOMS
When you try to make Distributed Component Object Model (DCOM) calls over a Network Address Translation (NAT)-based Firewall, you receive the error 0x800706BA (RPC_S_SERVER_UNAVAILABLE).



CAUSE
For DCOM to work, the client must be able to reach the server by its actual IP address. If you use firewalls that translate network addresses, the client cannot use the actual IP address to reach the server.

COM inserts the IP address of the server computer into the interface marshaling packets that are returned to the client. Instead of using the translated IP/header, Remote Procedure Call (RPC, or DCOM) uses the actual IP address to reach the server. Because the firewall prevents the client from directly accessing the server, the client receives the above-mentioned error message.

