To use NetMeeting (and other similar programs), special software 'ports' are used to signal and transfer data from computer to computer. These are different ports than are used for HTTP (web pages), E-Mail, and other 'regular' Internet Traffic.

Unfortunately, to enable certain 'ports' through a router you need to turn off the router's internal firewall. There are ways to enable specific ports on your router, but you'll have to talk to the manufacturer of the router for specific details.

If you do turn off the firewall, it is highly encouraged that you run a software firewall on each machine connected to the router...