IRC forwarding

[lycanthrope]

hello!

I have a router on LAN, connected to internet via DSL. there is another server on LAN, running local IRC. Now, i would like to enable users from internet to connect to LAN IRC via router. Router has a DNS registered domain,so it is accesible from all around the world. now only thing I don't know is how to enable users from internet to use IRC on LAN.
I am running 5.2.1 CURRENT. ipfw is the firewall.

thank you in advanced!

best regards,marin