Not a networking guy here, and this is nowhere near all you're asking for, but here's a classic GUI-controlled router setup which allowed me to totally block my son's internet access when needed. Sounds like your TV needs that too:

* Router was a Linksys WRT54GL [1] re-flashed with Tomato [2] firmware

IIRC it took two steps to stabilize things:

* One of the menu options [sorry, don't recall which one] allows watching the MAC and IP addresses of connected devices in real time as they come and go. You can somehow assign names to devices in this list to help sort them out. Unhook or power off off everything else or use the OUI lookup or somehow otherwise identify the TV. Click on 'static' so as to force Tomato's DHCP service to make the current IP address fixed for the TV's MAC.

* Now that the TV has a static IP on your LAN, you can use Tomato's 'Access Restriction' on that IP to disallow all outside access. Works as well for restricting one's kids' access to reasonable time ranges -- and cutting them off when necessary ;).

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[1] http://www.newegg.com/Product/Product.aspx?Item=N82E16833124...

[2] http://www.polarcloud.com/tomato