What I have is:
* Asterisk 184.108.40.206~dfsg-1ubuntu1,
* SPA112 ATA with analog fax in 1-st FXS port connected,
* SIP trunk with provider supporting T.38.
My network looks like this:
* spa112 (192.168.33.200/24) and Asterisk (192.168.5.253/24) in neighbouring LANs,
* Asterisk connects to the provider (220.127.116.11) via router
(18.104.22.168). Router has full DNAT to Asterisk server.
* The fax from SPA112 to Asterisk cmd ReceiveFax works well,
* The fax from Asterisk cmd SendFax to PSTN fax works well,
* However, the fax from SPA112 to PSTN fax doesn’t work. Using udptl debug, I can see packets between Asterisk and both sides (SPA112 and PSTN fax) but it seems that faxes can’t agree how to send image.
tcpenable=yes videosupport=yes transport=udp,tcp dtmfmode=rfc2833
qualify=yes directmedia=no allowguest=no alwaysauthreject=yes rtcachefriends=yes rtupdate=no callcounter=yes t38pt_udptl=yes,redundancy,maxdatagram 0
t38pt_rtp=no t38pt_tcp=no ignoresdpversion=yes disallow=all allow=alaw allow=ulaw externip