What you need to check for is the that the multiport module within the kernel has been selected and compiled in. You can find this option under:

Networking support —>
Networking options —>
Network packet filtering framework (Netfilter) —>

Make sure “Advanced netfilter configuration” is turned on, and then it’ll be under:

Core Netfilter Configuration —>
“multiport” Multiple port match support

I ended up having to recompile my kernel, but I’m glad I was able to figure this one out. The people in the #netfilter channel on Freenode were as helpful as usual (and by that I mean they were completely useless). The multiport module is great when you want to open multiple ports without having to use multiple commands, or for organizational purposes want to group multiple ports open. As from my example above you can see I’ve set port the HTTP and HTTPS port in the same line.