Fax not sent error: "Unknown RTP codec 100 received from..." What to do?

Question

Asterisk

Hello.
Asterisk (1.8) + iaxmodem + hylafax is configured on a server with Debian 6
A city number via SIP (ITL, UA) has been added to the asterisk.

[fax-out]
include => outgoing_calls

exten => _X., 1, NoOp()
exten => _X., n, Dial(SIP/ITL_out/${EXTEN})

When sending a fax, the asterisk console explodes:

NOTICE[6233]: res_rtp_asterisk.c:2334 ast_rtp_read: Unknown RTP codec 100 received from '_ip_voip_prov:26990'

And of course, the fax does not go through.
Google for two bottoms, but zero sense.
call for help)

Answer 1

and the other side knows how to t.38?
6) Unknown RTP codec 100 received:
You probably connected some fax to some ATA, and then try to send faxes over t.30 to asterisk, this is not good, this fails in almost all cases.
The real solution is to use a t.38 enabled ATA and patch asterisk to use t.38.