an outbound connection is established on any port from 6660 to 7000, it should allow inbound connections to that particular computer on port 113. This gives it more flexibility than static port forwarding because it is not necessary to set it up for a specific address on your network, allowing multiple clients to connect to IRC servers through the NAT-router. Security is also gained, in the sense that the inbound port is not left open when not actively in use. Disadvantages Port triggering has the disadvantage that it binds the triggered port to a single client at a time. As long as the port is bound to that particular client, port triggering is effectively unavailable to all other clients. In FTP file sharing, for example, this means that no two clients can download files from an FTP server running on "active mode" simultaneously. For IRC, even though the authentication step happens very quickly, the port triggering timeout may still prevent other clients from logging into IRC servers. Port triggering is unsuitable for servers behind a NAT router because it relies on the local computer to make an outgoing connection before it can receive incoming ones. On some routers it is possible to have more than one client use port triggering and port forwarding, but not simultaneously. See also Network Address and Port Translation NAT traversal Port forwarding References Routing Computer network security