Microsoft KB Archive/224196

= Restricting Active Directory replication traffic and client RPC traffic to a specific port =

Article ID: 224196

Article Last Modified on 11/6/2007

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APPLIES TO


 * Microsoft Windows Server 2003, Standard Edition (32-bit x86)
 * Microsoft Windows Server 2003, Enterprise Edition (32-bit x86)
 * Microsoft Windows 2000 Server
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Datacenter Server
 * Microsoft Windows Server 2003, Enterprise x64 Edition
 * Microsoft Windows Server 2003, Standard x64 Edition

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This article was previously published under Q224196





Important This article contains information about how to modify the registry. Make sure that you back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows registry



SUMMARY
By default, Active Directory replication remote procedure calls (RPC) occur dynamically over an available port through the RPC Endpoint Mapper (RPCSS) by using port 135. This process is the same process as in Microsoft Exchange. As in Microsoft Exchange, an administrator can override this functionality and specify the port that all Active Directory RPC traffic passes through. This procedure locks the port down.

When you specify ports to use by using the registry entries that are mentioned in the "More Information" section, both Active Directory server-side replication traffic and client RPC traffic are sent to these ports by the endpoint mapper. This configuration is possible because all RPC interfaces that are supported by Active Directory are running on all ports on which it is listening.

Note This article does not imply that replication can occur through a firewall. Additional ports must be opened to make replication work through a firewall. For example, additional ports must be opened for the Kerberos protocol. To obtain a complete list of the required ports for services across a firewall, click the following article number to view the article in the Microsoft Knowledge Base:

832017 Service overview and network port requirements for the Windows Server system



MORE INFORMATION
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

When you connect to an RPC endpoint, the RPC run-time on the client contacts the RPC endpoint mapper (RPCSS) on the server at a well-known port (135) and obtains the port to connect to for the service supporting desired RPC interface. This assumes that the client does not know the complete binding. This is the case with all AD RPC services.

The service registers one or more endpoints when it starts, and has the choice of a dynamically assigned port or a specific port.

If you configure Active Directory and Netlogon to run at "port x" as in the following entry, this becomes the ports that are registered with the endpoint mapper in addition to the standard dynamic port.

Use Registry Editor to modify the following values on each domain controller where the restricted ports are to be used. Member servers are not considered to be logon servers. Therefore, static port assigment for NTDS and Netlogon has no effect on them.

Registry key 1
Registry value: TCP/IP Port

Value type: REG_DWORD

Value data: (available port)

Registry key 2
Registry value: DCTcpipPort

Value type: REG_DWORD

Value data: (available port)

Administrators should confirm that if any intermediate network devices or software is used to filter packets between domain controllers, that communication over the specified port is enabled. Both the replication and the netlogon should be set to use different ports.

Frequently, you must also manually set the File Replication Service (FRS) RPC port because AD and FRS replication replicate with the same Domain Controllers. The File Replication Service (FRS) RPC port should use a different port. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

319553 How to restrict FRS replication traffic to a specific static port

If you are setting the Active Directory replication to a fixed port outside the range that is allowed for RPC ports to control access and logons through a firewall, the replication port and the dynamic RPC ports will have to be opened on the firewall to allow access and logons. This is because logon uses the Replication Port for user mapping.

You may want to set the Active Directory replication to a fixed port outside the range that is allowed for RPC ports. You may want to do this to control access and logons through a firewall. However, because of this, the replication and Netlogon port must be opened on the firewall. This is because the logon process uses the Replication Port for user mapping. 

For more information about the RPC Endpoint Mapper, click the following article number to view the article in the Microsoft Knowledge Base:

154596 How to configure RPC dynamic port allocation to work with firewalls

Keywords: kbenv kbinfo KB224196

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