Vat of Knowledge

They say you need to have a FE server in order to provide RPC over HTTP on an Exchange cluster, and it’s just not true.  Having a FE server makes things nice, because you can offer forms based authentication for OWA, and it can find mailboxes, regardless of which BE server they are on if you have more than one BE Exchange server.  A FE Exchange server also provides a layer of security as well, so I definitely recommend using a FE / BE solution if your company can afford it.  One thing I would have to say about a FE / BE solution, is that it does create a single point of failure if you only have one FE server.  They can be configured for load balancing, so that would be an option for some level of redundancy.

Here’s how to set up RPC over HTTP directly on the BE cluster.  Go to add/remove programs and click on Add/Remove Windows Components.  You will find RPC over HTTP proxy under Networking Services, just click details to see it.  Once installed open IIS manager, right click My Computer and click on Manage, expand Services and Applications and expand IIS, Websites, Default Website.  The proxy installs two new virtual directories, RPC and RPCWithCert.  By default it puts them directly under the Default Web Site, and therein lies the problem.  You need these virtual directories to be listed under the Exchange Virtual Server virtual directories in order to get it to work, as they are a resource.

Right click the RPC virtual directory, mouse over All Tasks and Save Configuration to a File.  Give it a filename and a password if desired.  Do the same for RPCWithCert virtual directory.  Now right click on the Exchange Virtual Server directory and mouse over New, Virtual Directory from File.  Browse to the files you just created, one at a time.  Click on Read File and then highlight it and click on OK.  Using the Cluster Administrator, move the group to force a failover to the other node(s) and repeat the process above.