How do you test your router/firewall for security?

[Larry Cook]

Now that I've moved to DSL, I was looking for ways to test the security of my 
router/firewall.  I'm going to use ShieldsUp! (http://grc.com), but was 
wondering what other tools were available.

When using a dialup connection, I felt pretty safe because of the seperation 
of my network and the internet, but now I'm more worried about something 
getting by my router.  I guess it's more that I have confidence in iptables 
and ZoneAlarm, but this Actiontec router is a blackbox to me, so I don't 
really have much confidence in it.

Thanks in advance for any suggestions.

Larry