Hot!Voip problem - DTMF rfc2833 not working

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2021/07/30 13:44:29 (permalink) 6.4

Voip problem - DTMF rfc2833 not working

Voip problem with DTMF
I have a Fortigate 60F and generally voip is working normal.
Except for the door-intercom.
The phones and the intercom are connected to an external sip server.
Calls can be made.
But to open the door, you have to response the call DTMF with dail 2 times zero.
Somehow the door-intercom don't received the DTMF code
If I call any other external number, with a IVR then DTMF is working normaly.
Now we change the DTMF standard in the phone to SIP INFO (RFC-2976) and not the default RFC2833
then the intercom is working. But tests to other external IVRs fail.
Of course i found things about the session helper.
But in the documentation also mentioned:
To use the SIP session helper you must not add a VoIP profile to the security policy. If you add a VoIP profile, SIP traffic bypasses the SIP session helper and is processed by the SIP ALG.
I have changed firewall policy's with voip profile strict / default / and without voip profile. no difference at all.
How to change the fortigate to working with RFC2833 ?

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    Re: Voip problem - DTMF rfc2833 not working 2021/08/02 03:33:25 (permalink)
    Did you restart the box when you enabled or disabled Session Helper?
    Are you using the Session Helper or the SIP ALG?
    fgt # show full-configuration | grep default-voip-alg-mode
    set default-voip-alg-mode proxy-based → SIP ALG
    set default-voip-alg-mode kernel-helper-based → SIP Session Helper
    I would disable both completely, reboot and test again.

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