Grandstream GXP1630 + GXP2170 on FreePBX | Unconditional Call Forwarding


Hi Grandstreaem Forum!

We run a bunch of GXP1630 and GXP2170 phones with our FreePBX 12.7.6-1904-1.sng7 (Asterisk 13.22.0).

The extensions in the PBX can be configured to forward calls using the “Follow Me” feature. This works fine.

The VoIP deskphone’s call forwarding feature does not work:

  1. Configure UCF (unconditional call forwarding) by keypad *72CFnumber#

  2. Phone’s display shows the CF symbol (handset with arrow to the right)

  3. Call Forwarding example:

Caller mobile phone (CLR-MB): 017512345678
Callee desk phone (CLE-DP): 0893579100 (100 is the extension)
CF mobile phone (CF-MB): 017198765432

CLR-MB calls CLE-DP -> CLE-DP doesn’t ring -> On the CLR-MB you can hear one single ringing tone, then the busy tone. The CF-MB doesn’t ring at all -> call has been terminated/aborted.

I compared the SIP traces of the succeeding PBX-CF to the failing CLE-DP-CF and noticed that the DIVERSION header is the culprit:

PBX-CF | Diversion:tel:+49893579100;reason=no-answer;screen=no;privacy=off

CLE-DP-CF | Diversion:;reason=unconditional

I know that the DIVERSION header in the CLE-DP-CF case is wrong, because our ISP (Vodafone) expects the value reflected in the PBX-CF result.

The question is: How can I make the Grandtream deskphone set the correct DIVERSION header on forwarded calls?

Thank you very much!

Best regards,


Are you on the latest firmware?

I’d open a ticket on that one as well as the forum conversation.


Hi @lstutesman!

Firmware is the current version

Just created a support ticket as you proposed. Thank you!


OK, the case has been clarified by the Grandstream Support:

The DIVERSION header’s format provided by the Grandstream VoIP phones meets the RFC5806 standards, but our SIP provider requires a different format for a successful authentication against their SBC.

There’s no way to manipulate or rewrite the header format.

This case is CLOSED.