As you say, the firewall rules can be pretty complicated. If you want to be able to validate whether you've configured your outbound rules correctly, you can use www.firebind.com. It has a simple web client you can plug TCP port ranges into to see if any firewall is blocking TCP connections from your machine to the Internet.

It's pretty handy whether you're trying to validate your own firewall rules or whether you're on the road and trying to figure out whether some other broadband provider (hotel, airport, coffee shop) is blocking ports you need.

ProtocolGeek

On the home routers I've seen the firewall is switched "on" but doesn't do anything unless you set up rules for it.

They sound like pretty pointless firewalls then!

Unless I mis-understand you.

Switched On, as in the NAT part is running, i.e. for simplicity many routers call the NAT part of the firewall.

Given NAT drops unsolicited incoming packets it does a pretty good job.

What rules would you like setting up out of the box?

NAT stops any incoming traffic unless you set up port forwarding.

What rules would you like setting up out of the box?

I'm not sure why you are asking me that question. I was simply questioning why a firewall would be switched on when it doesn't do anything.

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My zyxel router has a separate NAT and firewall. In my original post i was asking if there was any reason why I might use both my NAT and the firewall together. I currently believe the firewall has its uses but in my case and in my home network, it is unnecessary. My original question was to check my belief was correct. I currently run NAT with a couple of ports forwarded for outside access to my NAS and the firewall is disabled.