Asterisk 13, PJSIP And T38 Problem

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I need help to solve a problem that I am having using Asterisk 13, PJSIP and T38.

My setup is as follows:
SIP Provider –> Asterisk 13 –> Patton –> Physical Fax I need to get the fax directly in T38 to Patton.

The provider sends me the fax in T38. If I receive the T38 fax on Asterisk (using an hylafax device), I can properly receive the fax. If I send a T38 fax with Asterisk (using an hylafax device) directly to the Patton, I receive it correctly on the physical fax.

Instead, if I route, through Asterisk, the t38 fax call received by the provider to the Patton, I can not receive anything. From UDPTL debug I can see the flow of some udptl packages from the provider to Asterisk, but I see no udptl package from Asterisk to the Patton. From PJSIP logs, it seems that the T38 is properly negotiated by both parties. From the debug of the Patton i see many “Wrong media type. Drop FAX Packet”.

How to ensure that the fax, received by asterisk from the provider with T38 protocol, is routed to the Patton using again T38 protocol?

Below my pjsip.conf” file:


type=transport protocol=udp bind=


type=endpoint transport=simpletrans context=in_provider direct_media=no disallow=all allow=alaw allow=g729
aors=trunk-provider t38_udptl=yes t38_udptl_ec=redundancy t38_udptl_maxdatagram=400

type=aor contact=sip:X.X.X.X:5060

type=identify endpoint=trunk-provider match=X.X.X.X

type=aor max_contacts=5

type=endpoint transport=simpletrans context=in_patton direct_media=no disallow=all allow=alaw auth=trunk-patton aors=trunk-patton t38_udptl=yes t38_udptl_ec=fec t38_udptl_maxdatagram=400

type=auth auth_type=userpass password=XXXXX


Thanks Marco