Opening ports for remote access on ZyXEL DSL modem

I have to do this once in a while, then completely forget how it's done, and one year later, I spend 1 hour trying to figure it out again. Well, at least on the Prestige 660RU-T1 it's fairly easy from the web interface: NAT -> SUA Only and add something like:

	Start Port No.	End Port No.	IP Address
1	All ports	All ports
2

Oh and just in case you wonder, the only mode of authentication allowed from the outside is private key, so good luck trying to break in!