Firewall port open check

You might need to check whether some ports are open in an environment where Firewall are between servers.

Telnet is the tool to check the connectivity. Recently I was resolving one issue related to People search across multiple domains so I needed a tool to verify connectivity for ports 88, 139 and 445.

I used telnet to check, here is the command

telnet target_server_name_or_ip_address port_to_check

For example, log on to the server where you want to check connectivity from:

C:> telnet AD_SERVER_IP 88

There is another tool called PortQry that checks whether the port is listening or not, please visit http://support.microsoft.com/kb/816103

That's it.