Voip problem - DTMF rfc2833 not working

[corvdl]

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 ?

[mhe]

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.