Supporting Messaging Clients

Increasing NNTP Reliability Using a Master/Slave Configuration

Because Exchange 2000 clustering does not support Network News Transfer Protocol (NNTP) components, consider using a master/subordinate (previously known as master/slave) arrangement to increase NNTP reliability. A master/subordinate arrangement involves keeping newsgroup information on more than one server. Keeping newsgroup information on more than one server reduces the impact in situations where a server becomes unavailable. One possible configuration would be to use one master server and one or more subordinate servers. With such a configuration, you can configure your newsgroup DNS in two ways:

Note   When you set up your NNTP master/subordinate arrangement, configure a feed from each subordinate server to the master server. Do not configure any feeds between subordinate servers.

For example, Contoso, Ltd., a fictitious company that previously used only one server to store newsgroup information, decides to use a master/subordinate arrangement to increase reliability. Contoso configures its master news server ( to point to three subordinate news servers (,, and Contoso also configures round robin DNS so that users will gain access to newsgroups through either subordinate1, subordinate2, or subordinate 3. With this configuration, when a Contoso user connects to the newsgroups from his or her browser, he or she is routed to one of the subordinate servers (for example, subordinate1). When the user posts a message to subordinate1, the message replicates to the master server, and then the master server replicates the message to subordinate2 and subordinate3. That new message post is not available to any users (that is, the message cannot be seen by any of Contoso's users), until it successfully replicates to the master server. After the replication occurs, each subordinate server contains the same content.

Master Server or Subordinate Server Failure

If the master server becomes unavailable, users can still view the messages within the newsgroups. They can even create and submit new posts. However, any new posts created on any subordinate server while the master server is unavailable will not be available to any users. The new posts are not available because the master server has not replicated them to the subordinate servers. Each subordinate server holds any pending posts until the master server is available. After the master is available, it accepts any pending posts, and then replicates those messages to the subordinate servers. After replication occurs, each subordinate server contains the same up-to-date content. In this scenario, the only temporary interruption of service to users is that newly posted messages cannot be viewed.

If one of your subordinate servers becomes unavailable, and if you configured your NNTP to use round robin DNS, your users have full newsgroup functionality because they can connect to another available subordinate server. In this scenario, remove the IP address of the unavailable subordinate server from your round robin DNS configuration. After you remove the IP address of the unavailable subordinate server from DNS, users who connect to the newsgroups will be pointed to one of the available subordinate servers. If you do not remove the IP address of the unavailable subordinate server, users will continue to be routed to the unavailable subordinate server. If any of your users were connected to the subordinate server when it became unavailable, they must restart their browsers to continue using the newsgroups because they may have cached information specifying the now unavailable subordinate server. When the subordinate server becomes available again, you must reconfigure the NNTP round robin DNS to include the IP address of the subordinate server.

If one of your subordinate servers becomes unavailable and your NNTP does not use round robin DNS, your users who gain access to newsgroups through that unavailable subordinate server will lose all NNTP functionality. In this scenario, you must change your configuration so that users who access newsgroup information on the unavailable subordinate server can access newsgroups through one of your other subordinate servers. After the subordinate server is once again available, reconfigure your NNTP access to the subordinate server so that users can access newsgroups through their original subordinate server.

Master Server and Subordinate Server Newsgroup Hierarchy Considerations

When you use a master/subordinate arrangement, keep in mind the following considerations:

After you establish your newsgroup hierarchy, you should replicate it to the subordinate servers by doing one of the following:

Related Topics

Set Up a Master/Slave Configuration