I'm trying to add port forwarding for a few services on my iMac and haven't used the airport utility in quite a while, so after poking around, I found the port mapping settings (i.e. Airport Utility, Manual Config, "Network" Tab, "Port Settings" but the setting is greyed out and I can't click on the "+" to add a new service. A quick web search didn't show this as a common problem, so I'm wondering if anyone has experienced this with the latest airport utility and know of a fix?
Sorted out my own question. To resolve this kind of issue one needs to change the "Router Mode" setting from "DHCP Only" to "DHCP and NAT."