Mac Forum / General / Networking / June 2007

Router port forwarding is intended for incoming connection requests.  
Many services (.e.g IM) initiate connection by contacting an external
server, and so are initially outbound.  Do you intend to have internet
clients initiate connections directly to your computer?  If not, you
won't need to forward any ports.

Disabling the SSID and using MAC address filtering will *not* stop even
the most casual hacker from getting right into your router.  If you're
not using WPA security, your router is not secured in any meaningful way.

The short answer: If everything you use is working properly, leave it
alone.  It's fine!

The long answer:

Your internet connection from your cable or DSL company likely gives you
a single IP address that the world can connect to when you're online.  
When you're using a router to handle your internet connection, you're
creating a network-within-a-network.  That "local" network has a
completely separate set of IP addresses that will only work between
machines connected directly to that router.  (That's slightly
simplified, but basically correct.)

Say, for example, you have a web server (which uses port 80) running on
one of your computers.  If a connection comes in from the outside world
to port 80, it's going to hit your router and be ignored, because the
router doesn't know *which* computer can handle that connection.  
Setting up port forwarding is how you provide the router with the
information about which computers (in your local network) handle
requests from the outside world.

Most people won't need to touch the port-forwarding settings, because
most services (such as you sending or checking e-mail, or opening a web
page) are initiated as *outbound* connections from your computer.  Those
are processed automatically, no forwarding needed.  In most cases, port
forwarding is only necessary if you're setting up a server of some sort,
be it a web server, a file server, and so forth.

Hope that helps!

It ain't broke, don't fix it.