What settings do I have to change in WL500gP in order to be able to watch IPTV on any computer in LAN segment?

(Right now I use a secondary NIC on one computer, which is connected directly to ISP's switch, but only when watching TV on this computer. NIC#1 is connected to WL500gP for the "regular" internet traffic. I was hoping to optimize the whole thing to go through one NIC, using this router.)