I also saw your question on RFC compliance and the Sonus equipment: In order to make Grandstream phones register properly when using STUN behindsymmetric NAT, I had to patch nathelper with the rport != port of receivedaddress check. (I use 0.8.14 and I guess you already have the patch with the development version). The reason is that Grandstream attempts to rewrite the address using STUN even though it correctly detects a symmetric NAT. I have seen that this was introduced in a new firmware not long ago (release notes). This pussles me as sources I have seen claims this to beinvalid behavior (which seems correct to me).

It seems that I am facing the same problem now. Is there any solution to us? Where could I download the nathelper patch as described above?