How to configure DFS to use fully qualified domain names in referrals

A Windows 2000-based server that is using Microsoft Distributed File System (DFS) replies to a DFS "get referral" query with a NetBIOS name format (\\server\share) by default. This is necessary in certain environments in which NetBIOS is relied upon.

Depending on the client's Domain Name System (DNS) configuration, the client may not be able to resolve the server name returned from the DFS "get referral" query.

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:
To modify this behavior, use any of the following methods:

• Configure a DNS suffix for resolution of unqualified names on the client.
• Add a DNS entry for the server name in the client's DNS zone.
• In a DNS-only environment, configure the DFS server to respond with a fully qualified domain name by setting the DfsDnsConfig parameter in the registry.

To enable fully qualified domain names in DFS:

1. If the DFS server hosts a DFS root or replica, remove it from the server. (If you accidentally activated the DfsDnsConfig parameter without removing configuration information, you can clear it by typing dfsutil /clean: computername.
2. Start Registry Editor and open the following key:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dfs
3. If you find a DfsDnsConfig value, click Edit Value on the Edit menu, and then change the value to 1. If there is no DfsDnsConfig value, click Add Value on the Edit menu, and then add the following information value:
   Value Name: DfsDnsConfig
   Data Type: REG_DWORD
   Value Data: 0 or 1
   If you set the data value to 1, all roots added to the DFS tree use a fully qualified domain name. 0 specifies the default behavior.

Note This registry Key takes effect only after the DFS Service is restarted.
Note When you are using either the Microsoft Management Console (MMC) or dfscmd to update the DFS links, you may receive an error that says that the links could not be updated if the DFS is domain based. In a domain-based DFS scenario, use the following steps to enable the use of FQDNs in DFS referrals:

1. Remove all DFS root replicas for the domain-based DFS.
2. Make the registry change as noted in the "To enable fully qualified domain names in DFS" procedure earlier in this article.
3. Re-create the domain-based DFS.

Working with DFS in an environment without WINS

The default behavior of DFS is to use NetBIOS names for all network shares that are configured in the DFS namespace. This makes it possible for clients that support NetBIOS-only name resolution to locate and connect to targets in the DFS namespace. However, clients that do not use NetBIOS do not work in this environment. DFS can operate in a DNS-only environment, where all the computers understand fully qualified names. The DFSDnsConfig registry key must be added to each server that will participate in the DFS namespace for all computers to understand fully qualified names. This registry key should be added to the servers before the DFS namespace is built. This makes it possible for the clients to see fully qualified names when they are referred to other servers as part of the DFS referral process.

Note Use extreme caution when you set this registry key. If this key is not set on all DFS servers, or if it is set on servers that operate in a hybrid environment of DNS-only and NetBIOS-only, access to the DFS namespace could be severely affected.

Removing and re-adding DFS

Using the DFS administrative console to remove the server from DFS, and then add it back again, may have the following undesirable results if File Replication service (FRS) is used for replication.

• Removing the server from DFS causes the server to be removed from the FRS replica set.
• Adding the server back into the DFS configuration causes FRS replication to go into effect for that server and replicate all data.

This problem can be avoided by using the DFS tools to remove the server and then add it back into the DFS namespace. To do this or other actions, use one or more of the following methods.

• To remove a target (\\Member\Share) from a link in the DFS configuration, type DFScmd /remove \\Domain\DFSRootName\linkName \\Member\Share at a command prompt, and then press ENTER.
• To add a target back into the DFS configuration, type DFScmd /Add \\Domain\DFSRootName\linkName \\Member\Share at a command prompt, and then press ENTER.
• To remove a target (\\rootSrv\rootShare) from the root in the DFS configuration by using DFSutil, type DFSutil /Remroot:DFSName /Server:rootSrv /Share:rootShare at a command prompt, and then press ENTER.
• To add a target back into the DFS configuration, type DFSutil /Addroot:DFSName /Server:rootSrv /Share:rootShare at a command prompt, and then press ENTER.

Warning Do not use the Remroot option if the root target that is being removed is the only root target for the DFS namespace. Doing so causes the entire DFS namespace to be removed.

For more information about related topics, see the "Distributed File System (DFS): Best Practices and Troubleshooting Guide" at the following Microsoft Web site: