T38 Pass-Through will not enable on pjsip

I recently setup FreePBX and it is overall working great. Thank you for a great open source product. I currently have two issues I am trying to resolve, so I have split them in to two separate posts for ease in addressing them and for future readers seeking solutions to the same or similar problems.

I am using a pjsip trunk with provider Flowroute. I can inbound and outbound voice calls just fine. I want to enable T38 for FoIP. Flowroute advertises support for T38 (I am not allowed to add the links. I can toggle settings under the trunk, but there is an issue with the T38 Pass-Through setting under Asterisk SIP Settings. I can currently fax successfully over g711 but I want to test T38 for what should be superior reliability. If I make any changes to T38 settings for the trunk, faxing fails. I can only assume it is due to the issue related to enabling T38 Pass-Through in Asterisk SIP Settings.

If I change to anything other then “No” (I have tested all available options), submit and apply config, and then return to the Asterisk SIP settings page, the field will have returned to the original “No”. The setting change will not take. Should I open a ticket? Am I doing something wrong?

Since I haven’t heard anything or made any progress, I went ahead and opened an issue.

There was no need to open an issue. It’s been 1 day since you posted and it is a weekend.

The T.38 setting under Asterisk SIP Settings shouldn’t be there anymore, it should be moved under Chan_SIP settings as that is what it really applies to. PJSIP does not have globally inherited settings, they need to be set per endpoint (in this case, your trunk).

Under the Advanced tab in the PJSIP Trunk settings you will see the T.38 setting options for the trunk. You need to enable it there and then test.

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