Hi there,
I’m running Asterisk 13.25.0 (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 1480777904 1480777905 IN IP4 <internal ip>
s=Asterisk PBX 13.25.0
c=IN IP4 <external ip>
t=0 0
m=image 4902 udptl t38
c=IN IP4 <internal ip>
a=T38FaxVersion:0
a=T38MaxBitRate:14400
a=T38FaxRateManagement:transferredTCF
a=T38FaxMaxDatagram:849
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.