I work with a number of SQL servers. Some are clusters and some are standalone. Some of the standalone servers run multiple instances and some do not. What I've found is that any SQL server I have running will not respond to a telnet on 1433 unless they are a standalone server with a single instance running. I've disabled the firewall, verified port configuration in the SQL configuration tool, verified remote connectivity is enabled, and checking netstat shows the server is listening on the proper port.
I have no issues connecting to any of the servers with the SQL Management Studio. Why is telneting to these servers on 1433 fail? Is there some configuration I'm missing?