[CentOS] OT: closing a port on home router

Hi all!

I'm wanting to close port 22 (ssh) on my home router, and I don't see any
facilities in its GUI for doing that.

I don't mind learning how to write an iptables rule for that, but I'd
rather not have to fool around with commandline stuff on the router,
especially things that require extra steps to make it peresist across
boots.

So, I'm trying this (please tell me if it makes sense to do it this way):
I've set up a port forwarding rule on the router that forwards incoming
port 22 to port 9 on the LAN side of the router. As I understand it, port
9 is a /dev/null equivalent, and it seems to block the port well enough,
but are there caveats I should be aware of?

thanks!

BTW, this is an Asus RT-N16 router using their latest released firmware.

Fred

-- 
---- Fred Smith -- fredex at fcshome.stoneham.ma.us -----------------------------
                        The Lord is like a strong tower. 
             Those who do what is right can run to him for safety.
--------------------------- Proverbs 18:10 (niv) -----------------------------