Situation: I believe that multiple port 1433 can be implemented as long as the IP address are all unique.

I’ve created SQL Server 2008 R2 SP1 clustered virtual instance on top of my Windows Server 2008 R2 SP1 Enterprise MSCS, one instance is working fine and I can perform:

C:\telnet SQLClustername-instance1 1433


However with the other instance I cannot perform the above command and it is not accessible at all ? pinging the SQLClustername-instance2 is fine and reply back, when I do the following command:

C:\netstat –ano | find /I “1433”

I cannot see the SQLClustername-instance2 IP address with port 1433 listening ?

Any assistance would be greatly appreciated.


  • 1
    I'm not sure 2 instances can share the same port, but that aside for a moment, I think the easy thing to do first is verify what ports each instance is running on. Use SSMS and try connecting but use IP,Port# instead of name. Then look at @@SERVERNAME or one of the SERVERPROPERTY functions and see what instance you're on. Attacking this from the other angle, you could connect by instance name and then run this query to see what port SQL is listening on: "select distinct local_tcp_port from sys.dm_exec_connections where local_tcp_port is not null"
    – Henry Lee
    Apr 10, 2012 at 14:16
  • Are the instances in separate subnets? Apr 10, 2012 at 14:38
  • Hi, so in this case there can be only one instance listening on port 1433 ? From the SQL configuration manager, the instance2 ip address it is set 0 as dynamic port. My BiztalkServer 2010 cannot somehow talk to this instance2? So should I make it explicitly 1433 instead of 0? Apr 10, 2012 at 22:16

1 Answer 1


Does the SQL Server instance installed on the cluster resource named SQLclustername-instance2 listen on port 1433? If you installed a named instance then is very likely using dynamic ports. See Configure a Server to Listen on a Specific TCP Port.


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