Since I was installing a dual instance cluster, I had setup two virtual SQL database names with different IP address and the second instance required a non-default instance name. However, I wanted to access both instances using the virtual name and I found I could do that by setting both of them to listen on port 1433. Now SSMS and other applications can access the second instance using only the SQL server name.
For example,
SQLCLUST2012 – default instance name
SQLCLUST2008\SQL2008 – named instance
Can now be accessed simply by their SQL virtual database name
SQLCLUST2012
SQLCLUST2008
Accessing a clustered SQL Server instance without the instance name.
Note: some problems have been noted with older tools accessing the instance name in this manner.
More details can be found at Ryan McCauley’s blog
Another method for non-clustered servers with multiple instances is to establish an alias for each instance.