If you want to access an iLO behind a firewall, there are some TCP ports that need to be opened on the firewall to allow all iLO traffic to flow through. ┬áHere is a list of the default ports used by iLO, but these can be modified on iLO’s Administration… Access… Services… tab.

ILO FUNCTION           SOCKET TYPE PORT NUMBER 
---------------------- ----------- -----------
Secure Shell (SSH)         TCP        22
Remote Console/Telnet      TCP        23
Web Server Non-SSL         TCP        80
Web Server SSL             TCP        443
Terminal Services          TCP        3389
Virtual Media              TCP        17988
Shared Remote Console      TCP        9300
Console Replay             TCP        17990
Raw Serial Data            TCP        3002

Here’s a screenshot of the iLO configuration page for these port numbers:
ilo-services