Adding a Back-End Server to an RPC over HTTP Deployment
When your Microsoft® Exchange Server 2003 SP1 front-end servers are configured to act as RPC over HTTP front-end servers, they will automatically detect and publish any additional back-end servers that you later configure as RPC over HTTP back-end servers. For example, if you upgrade a server running Exchange 2000 Server to an Exchange 2003 server and need to allow RPC over HTTP access to that server, configure it as an RPC over HTTP back-end server and it will be published automatically. You do not need to restart any services. However, because you are working with Active Directory® directory service properties, you may need to allow for replication latency before the front-end server detects the changes. Additionally, the front-end server updates its RPC over HTTP target details every 15 to 20 minutes.
For more information about how to configure a back-end server to act as a target for the RPC proxy server, see How to Configure the Back-End Server to Act as a Target for the RPC Proxy Server.