In my last post I covered remote SQL servers with non-default ports. But, what if you have a remote SQL server with a named instance? Named instances have different requirements. In this case, you must use dynamic ports.
First, you will need to open the new port in the firewall.
Next, in SQL Server Configuration Manager, navigate to Protocols for MSSQLSERVER.
Open the TCP/IP Properties page.
Clear all the TCP Ports. In the IPAll portion, set the TCP Dynamic Ports to the port you will be using.
Now that the port is set, configuring the Configuration Manager setup and later the Reporting Services Point, will ensure that they will communicate with SQL on the desired dynamic port.