To configure the iLO3 networking for the first time you will need to locally administer the system or have access to the serial console via remote connectivity.
You will need to bring the system down. No users can be on this system during the initial configuration of iLO.
During POST press the space bar to see ROM configuration options. Press F8 when prompted to modify the iLO settings. You can change the iLO networking and user information here.
Once you have configured the networking you should be able to use the http interface or the command line to do any further configuration and troubleshooting.
Since I ran into this issue you may as well:
If you cannot activate the iLO license using the http interface, you may need to do it via the command line and the following steps should work fine.
Make sure that iLO can ping no matter what type of configuration you are working on.
From the command line type: oemhp_ping
Have your license key handy and type the following command:
set /map1 license=
You can also reset iLO3 using the following command:
start /map1 reset