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corvdl
corvdl
New Member
July 30, 2021
Question

Voip problem - DTMF rfc2833 not working

  • July 30, 2021
  • 1 reply
  • 3854 views

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 ?

 

 

 

 

 

 

 

 

 

 

1 reply

mhe
mhe
Explorer II
August 2, 2021

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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