Originally Posted by
bungiefanNA
Your router is a firewall, because of NAT. It acts as a bouncer, and incoming traffic isn't sent to a device on the other side of the router unless it was specificlaly requested by the device. Port forwarding tells the router to allow traffic into the network on specific ports (each IP address has 65535 ports each for TCP and UDP traffic) , and to direct it to specific devices. Since it's a one-external-address-to-many-internal-addresses mapping, each port has to be specified to a specific internal IP. If no address is specified, the router discards the data.
You should know the IP address of the PS2, because you get to set it in the configuration in PlayOnline Viewer. You can either have devices request an address from the router (auto-configure, dynamic) or set the address on the device itself (manual, static). You want to set it yourself, because the router can hand out from a pool of several addresses, and it picks them randomly, so when you turn the PS2 off, it can get a different address next time. Setting the address yourself lets you know what it always is, and thus keep the port open for it.
Find a Network+ study guide. This is a major component of that exam. As for how to do it on your router, that varies from router to router. All network devices have the same settings options though, so defining a static address is the same, though the interface itself may be different.