I am have 10 GrandStream 2130s and two 3275 models. I run FreePBX and I am don’t understand why but the 2130s do not recognize the “Call Answered Elsewhere” instructions sent to the phones when a call is picked up from a ring all ring group. The 2130s simply mark it as a missed call. It The 3275s recognize the that the call was answered elsewhere and do not log it in the missed call logs. I have configured both models with the same basic configuration, the only difference is the phone models.
After talking with Grandstream support, they said it may have something to do with the "“reason: Q.850;cause=26” being included in the cancel header. I also found this link for Yealink phones that seem to be experiencing the same issue. forum.yealink.com/forum/printthread.php?tid=12401
Any suggestions because I do not know how to setup a SIP Proxy server.