I don't know about any of you, but whenever we need to have our ESX hosts firewalled off from the vCenter infrastructure services (such as vCenter; Updatemanager...) and you do not control the firewall it can be a rather painful process in verifying the firewall group has actually opened up the ports you requested. Even more so since Telnet is not part of the ESXi "console".
vSphere Admin: Please open ports.............
Firewall Admin: Ports opened
vSphere Admin: I still cannot connect are you sure you opened them?
To help you verify that your ESXi hosts can connect to your infrastructure services and the firewall ports are in fact open, I came across this python script (attached). Upload the python script to your /tmp and follow the directions with the .txt file in the zip.