Domain DFS does not support alternate site coverage (225228)

SUMMARY

In Active Directory, site-aware client computers can discover and use domain controllers in the same Active Directory site for logon authentication, password changes, domain or global catalog queries, and other operations.

Active Directory also supports alternate site coverage in which you either implicitly or explicitly configure domain controllers in one Active Directory site to respond to client requests in another Active Directory site. This site is typically a site in which a domain controller does not exist.

Windows 2000 domain Distributed File System (DFS) servers also support site preference, which allows site-aware DFS clients to discover and use targets for both DFS root and child links in the same Active Directory site and DFS targets in the same Active Directory site as the DFS client. However, DFS does not support alternate site coverage.

An update for Windows 2000 Server is available that forces clients to use their authenticating domain controller to obtain SYSVOL data. This feature leverages the alternate site coverage that is provided by Active Directory. The feature is activated by the DfsEnableSmartClient registry key. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

823362 Sites without domain controllers cause DFS referral to remote site for SYSVOL contents

MORE INFORMATION

A recent DFS white paper states the following information about the point of alternate site coverage in DFS:

If no replicas exist in the same site as the client, but another site is defined to provide Site Coverage for the clients site, then one of the Replicas in the "covering site" will be selected at random.

This statement is incorrect because alternate site coverage or fail-over to a regionally desirable DFS target in another Active Directory site does not occur in Windows 2000 domain DFS. Site-aware DFS clients that access domain DFS roots and links receive a referral that contains a randomized list of targets in the same Active Directory site as the client. This list is displayed at the top of the referral list and is followed by a randomized list of targets in the DFS replica set in other Active Directory sites. The client "walks" the list of servers in its Active Directory site. If a same-site referral does not exist, the DFS client connects to the first server in the "out of site" list that it can reach. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

260857 DFS site information is not updated when you move server to a New Active Directory site

262289 Invalid DNS Records Are Not Removed

274411 Console and Terminal Services access to DFS share ignores site preference