I'm having issues with my grandstream HT502 where I get a busy signal, dead silence or messages saying "this caller is unavailable".

I have the correct UDP ports forwarded in my router, but have been wanting to put the grandstream in front of my router.

I want to keep my firewall settings on my router, but just want to make the grandstream a pass-through or bridge? Anyone have this setup?

Any help is appreciated!

Justin