DTMF is working but"show voip rtp session named-event" shows no output

[ilyas.safarov]

Hi All,

I've faced with a situation when I call our number from PSTN DTMF is working but "show voip rtp session named-event" shows no output.

INVITE SDP received from telco:

v=0
o=- 3838370 8411136 IN IP4 x.x.x.x
s=-
c=IN IP4 x.x.x.x
b=AS:0
t=0 0
m=audio 11538 RTP/AVP 8 0 96
b=RR:0
b=RS:0
a=rtpmap:8 PCMA/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:96 telephone-event/8000
a=fmtp:96 0-15
a=ptime:20
a=sendrecv

Can anyone clarify this for me. Thanks in advance.

[Maren Mahoney]

Check with your service provider regarding which RTP payload code they want for rtp-nte. When I have seen rtp-nte used, the code is generally 101 and not 96.

Maren

[Valeriy Kuznetsov · Accepted solution]

There were some architecture changes between ISR G2 and G3, so in G3 (4k) the command "debug voip rtp session named-event" would not generate any output even though everything works fine. 

There's enhancement request for same to be implemented - https://bst.cloudapps.cisco.com/bugsearch/bug/CSCtz60693 

To troubleshoot rfc2833/nte dtmf issues the only way to use packet captures.

BR,

Valeriy

[ilyas.safarov]

Thank you very much for clarification Valeriy. Very appreciate it.

Regards,

Ilyas