Auuugh! I finally got it.
I found the need to use NAT loopback – a.k.a. hairpinning – on my home router. I have an application running where I need to be able to access it from home and elsewhere without having to worry about having to switch between the WAN ip address and the LAN ip address.
Most home routers don’t allow this at all. And actually, I’d been searching up and down to maybe purchase another device (like I really need more junk around here, right?) that could do it. Maybe one of those fancy routers that supports OpenWRT. A business-class something. And lo and behold, those guys at Frys or Micro Center almost had my hard earned cash, but curses, they’re foiled again.
Now, I’d seen this in the D-Link router settings (I have a DIR-655) but never really knew the difference. To really use this device, I guess you have to have written instructions in somethingese, and I was lacking.
So this router has settings for “virtual server” and also “port forwarding”. They look the same, but they aren’t.
Anything set up on “virtual server” will use NAT loopback. Anything set up on “port forwarding” will not. Wow, that was simple.
Thanks to Dan Larsen, who seems to have beat me to the punch by just a few months.