I came across this doing an on-line search and the info was helpful to setup my DIR-615 router.
Here's what I did:
1) Setup an "Inbound Filter" under advanced settings for IP 126.96.36.199 as "Remote IP Start"/End, saved as "Directv STB Services" (don't forget to save prior to moving along) and went to Advanced/Port Forwarding,
2) Port Forwarding settings: Enter STB TCP port of DVR (ex. 27161), named it DVR location (ex. LR STB port), entered IP as DVRs IP address (192.168.0.249), selected my "Inbound Filter" (Directv STB Services) and enabled it, then saved.
What happened? I went to Network Setup/ Network Services and selected "manual" mode and entered 27161 as STB port and 27162 as audio services. Selected connect and it setup successfully with the Congrats message from Directv.
I only had to forward the STB services port to connect successfully and was able to verify TV APPS and VOD downloads successfully, even an HD VOD from History Channel loaded with audio. Best I can tell, this is all that is necessary. But I also wanted to only have the port open when needed so I used the "INBOUND FILTER" as a trigger of sorts to limit access to that IP only, I hope.
I thought I would post my results here since the info posted by the OP helped. Good Luck!