[Asterisk-Users] DTMF errors

[Michael Welter]

I'm getting the following messages when a call is answered by a SIP device:

Nov 28 13:03:01 NOTICE[22824]: rtp.c:1146 ast_rtp_raw_write: RTP 
Transmission error to 192.168.1.254:19262: Operation not permitted

For a Cisco 7940 line, I have the following sip.conf entry:

[desk2]
type=friend
username=desk2
secret=xxx
host=dynamic
dtmfmode=rfc2833
context=international
canreinvite=no
callerid="xxx"<3034144980>
mailbox=701 at xxx
nat=yes
qualify=yes
accountcode=xxx
disallow=all
allow=ulaw
allow=g729

The Asterisk system faces the Internet on a public IP.  The phone is 
behind NAT.

Asterisk version is 1.0.7.

What can I do to fix this problem?

Thanks,