On mine the way I received it from VOIPo, the WAN side had the HTTP management interface enabled. It is configurable to enable or disable from entering in touch tones per the quick setup guide. I guess that is why I could get to the management HTTP via the WAN interface, even though the WAN is connected to my LAN. Confusing huh!

Also, it looks like you can static IP the WAN port IP address. It has DHCP, PPPOE, or Static. You would just need to put in a static IP from your LAN on the WAN configuration of the 502 and it should work. I didn't need to make any other changes.

scott