I’m running Asterisk 13.6.0 (chan_sip), behind a NAT.
I’m trying to configure T.38 support, and it works, sort of, however the SDP Asterisk sends out when trying to RE-INVITE to UDPTL contains two c= lines, one with the external, and one with the internal IP.
I’ve set the following settings in sip.conf:
t38pt_udptl = yes t38pt_usertpsource = yes
The SDP in the re-invite looks as follows:
v=0 o=root 1933471796 1933471797 IN IP4 <external ip> s=Asterisk PBX 13.6.0 c=IN IP4 <external ip> t=0 0 m=image 4404 udptl t38 c=IN IP4 <internal ip> a=T38FaxVersion:0 a=T38MaxBitRate:14400 a=T38FaxFillBitRemoval a=T38FaxRateManagement:transferredTCF a=T38FaxMaxDatagram:1400 a=T38FaxUdpEC:t38UDPFEC
Is there some way to get rid of the c= line with the internal IP?
I suspect this is the reason why we’re seeing A LOT of errors receiving faxes when T.38 is enabled.