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Configuring Microsoft Distributed Transaction Coordinator (DTC) to work through a firewall
Article ID: 250367 - View products that this article applies to.
This article was previously published under Q250367
This article describes how to configure Microsoft Distributed Transaction Coordinator (DTC) to work through firewalls.
You can configure DTC to communicate through firewalls, including network address translation firewalls.
DTC uses Remote Procedure Call (RPC) dynamic port allocation. By default, RPC dynamic port allocation randomly selects port numbers above 1024. By modifying the registry, you can control which ports RPC dynamically allocates for incoming communication. You can then configure your firewall to confine incoming external communication to only those ports and port 135 (the RPC Endpoint Mapper port).
You must provide one incoming dynamic port for DTC. You may need to provide additional incoming dynamic ports for other subsystems that rely on RPC.
The registry keys and values described in this article do not appear in the registry by default; you must add them by using Registry Editor.
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/322756/ )How to back up and restore the registry in Windows
Follow these steps to control RPC dynamic port allocation. You will have to do this on both computers. Note also that the firewall mustbe open in both directions for the specified ports:
For more information, click the following article number to view the article in the Microsoft Knowledge Base:
217351For more information about LMHOSTS files, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/217351/ )DCOM port range configuration problems
(http://support.microsoft.com/kb/102725/ )LMHOSTS file information and predefined keywords
For more information concerning using DCOM and RPC with firewalls, consult the white paper by Michael Nelson, "Using Distributed COM with Firewalls," which is available at the following Microsoft Web site:
Article ID: 250367 - Last Review: December 3, 2007 - Revision: 3.2