Iptables is a powerful administration tool for IPv4 packet filtering and NAT. It is used to set up, maintain, and inspect the tables of IP packet filter rules in the Linux kernel.
Iptables commands can be entered by command line interface, and/or saved as a Firewall script in the dd-wrt Administration panel. I tend to recommend testing and confirming your rules at the command line first. This way, if you happen to make a big mistake (like blocking access to the router), simply rebooting the router should repair it rather than having to do a hard reset. To get your rules to survive a reboot of the router, save them in a Firewall script as mentioned earlier.
I think we should have something about Firewall Builder on this page, since they're kind of related...
