I installed cpanel on a fresh installation of centos 5.
turned off firewalls.
when typing the IP address in the browser I can see the cpanel/whm welcome page.
Great Success !
Apache is working on your cPanel® and WHM™ Server
but when typing the port number to login for the first time to whm, it says:
Unable to connect
Firefox can't establish a connection to the server at IP ADDRESS:2086.
* The site could be temporarily unavailable or too busy. Try again in a few
* If you are unable to load any pages, check your computer's network
* If your computer or network is protected by a firewall or proxy, make sure
that Firefox is permitted to access the Web.
Note: I have my server right beside me connected to net with a dedicated IP address.