t38 FAX codec in FreePBX

I have received some requirements regarding Fax codec t38 on FreePBX with SIP service provider, spending some times to figure it out how should enable the t38 so here is the summarized outcome of my experience.

First of all we will need a trunk in FreePBX so here is the minimum parameter we need to have in the trunk setting:

username=SIP_USERNAME

type=peer

secret=SIP_PASSWORD

qualify=yes

nat=yes

insecure=port,invite

host=sip.t38fax.com

defaultexpiry=300

port=

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Incoming -> Register String

 

SIP_USERNAME:SIP_PASSWORD@sip.t38fax.com:5080/SIP_USERNAME

 

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Then you we need to enable the t38 Pass-Trough in the FreePBX setting >> Asterisk SIP Setting:

T38 Pass-Trough enable

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Next we need to get access to CLI and modify the udptl_custom.conf file to look like below.

udptlstart=10000

udptlend=10999

udptlchecksums=no

T38FaxUdpEC=t38UDPRedundancy

udptlfecentries=3

udptlfecspan=3

use_even_ports=no

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After all this setting you need to reload the FreePBX using below command in CLI

fwconsole reload

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