I tried to hook up my voip phone (spa2102) to the dir-615 (hardware : C1 , frameware : 3.11NA)  I can sync up the voip.  However, no successful in coming and out going call can be made.  The sympton is - 
Outgoing call - death silence, the destination party no ring tone. 
Incoming call - ring, after off-hook, it is silence. the calling party always hear ring tone even the called party pick up the phone. 
I have tried - disable the SPI, upnp, sip, ..., . 
Is ther anything I can try?  Please advice and Thanks in advance.