Making a SQL Server Instance Listen on Multiple Ports

Sometimes when upgrading a SQL Server instance to 2005 or 2008 named instance there is still a need to support a legacy application which can only talk to the default instance on port 1433. Normally I handle this scenario in the following way.

(1) Install a named instance and set it a static TCP port (under IP All). (for example, 4532)
(2) Configure a "default" alias to point to the named instance.What I'm calling a "default" alias is an alias named as the server name and assigned to port 1433.

This allows you to access the instance through a number of ways.
ServerName\NamedInstance
ServerName\NamedInstance,4532
ServerName,4532
ServerName
ServerName,1433

This allows SQL to "listen" on multiple ports. Keep in mind based on which options above you choose, you may need Shared Memory enabled as a protocol as well as the SQL Server Browser service enabled. Generally, I use the static ports only and turn the browser service off for a more secure installation. In addition, since I generally remotely connect to a SQL instance, I turned off the Shared Memory protocol.