Trunk Calls


Good afternoon. I am using a GPX1625 with a SIP account from I configured the phone at home and everything works as expected – incoming and outgoing calls, SIP encryption, etc. However, when I take the phone to the office, it begins to ring constantly saying (INCOMING CALL TRUNK 6) x 3 on the screen. The calls can’t be answered. We do have Polycom IP phones on the same network that are provided by our local phone company. Since this happens only at the office, the Grandstream phone must be picking up some kind of SIP trunking traffic from the telco IP system. We do not have a PBX or any phone system, our IP phones are directly connected to the telco’s IP phone switch (Genband C15) via our fiber connection. This also must be picking up layer 2 traffic because the Grandstream phone is setup on our data subnet, and the phones are on a different subnet.

Can I change a setting in the Grandstream phone to ignore this other SIP Trunk traffic from our telco system? We are hoping to add a few new phones, and eventually switch to our own IP PBX. Any suggestions would be greatly appreciated.


you probably get phony “invitations” on the phone, I won’t dwell on the problem, try to look at the item “Only Accept SIP Requests from Known Servers”


Interesting, thanks. I’ll try that and see if it works tomorrow. I assume this setting is not enabled by default?


@damiano70 Thank you for the information – it worked perfectly!