Network Firewall Help?

I'm trying to run a small Minecraft server, but I am encountering issues with my router.
I am currently using an ASUS RT-N12 (connected via cable rather than wireless). The server does run properly while the router's firewall is disabled. However, enabling the router's firewall prevents the server from binding to its designated port despite the port being forwarded, and causes any port checking utilities I look at to detect all ports as being closed.
The router settings do not appear to have any options available for adding exceptions to the firewall. Is disabling the firewall really the only way that I can run my server? Or am I missing something terribly obvious?