As a follow-up to my last post, I figured out what the problem was which was preventing my Grandstream FXS device from registering with Galaxy Voice over my dryloop DSL account.
I'm using an OpenWRT wireless router, and the Grandstream for whatever reason wasn't seeing it and detecting the NAT as open internet, which is incorrect. I couldn't find any way to override the NAT detection, so I instead turned off NAT transversal, and it worked. The device is now registering with Galaxy Voice. Awesome!
