If you really *are* looking for the IP address (and not MAC address), it is probably 0.0.0.0 as set at the factory.
To see the IP address, go to Setup-->Network-->Wireless Network.
In my experience, the non-zero IP is not known until you connect to your wireless network (assuming it is assigned via DHCP).
If you meant MAC address, it can be found under Network Connection Test.
I'm trying to connect my BD-P3600 with my wireless network, so far without any success. I'm reading that I need to open three ports on my wireless router, but this requires entering the IP address of the Blu-Ray. How do I find it?