Default Codec for Voip Dial-Peer: G729

I didn’t know that! The default codec used by the voip dial-peers is G.729, I got the proof when I was calling from a PSTN phone towards H.323 branch router over T1 and passing it to central CUCM over voip. And also this was the reason I was not getting MoH at PSTN because MoH stream was multicasting over G711 only! Though my H.323 gateway and the destination phone was located on the same region but the call was establishing over G729. Then I found the issue after seeing the result of the command ‘sh voice call summary’:

Branch#sh voice call summary
PORT           CODEC     VAD VTSP STATE            VPM STATE
============== ========= === ==================== ======================
0/0/0:23.1      g729r8 n  S_CONNECT             S_TSP_CONNECT’

I was so surprised!! It’s the root cause my MoH is not working!!! I just asked one of my friend (Olivier: about the issue, he smiled and told me it’s normal to use g729 by default for the dial-peers unless I change from the voip dial-peer towards CUCM. Hats of my friend! I just changed the codec to G711 and it’s was working like magic.

dial-peer voice 9 pots
translation-profile incoming PstnInStripTo4
incoming called-number .
dial-peer voice 90 voip
destination-pattern 3…
session target ipv4: ! CUCM IP
codec g711ulaw
no vad

After configuring that:

SB#sh voice call summary

PORT           CODEC     VAD VTSP STATE            VPM STATE

============== ========= === ==================== ======================

0/0/0:23.1      g711ulaw n  S_CONNECT             S_TSP_CONNECT

0/0/0:23.2      –          –  –

And my MoH issue is fixed! It was a good learning for me. 🙂


About Mijanur Rahman
Mijanur started blogging to save and share his study and research notes. A deep diver in technologies and loves to participate in technical brainstorming. Proud father of two wonderful daughters loves to spend time with them. He writes about the topics that people deal with every day mainly on technology arena. To get in touch contact him at

5 Responses to Default Codec for Voip Dial-Peer: G729

  1. lakshman says:

    i am testing voip in wimax CPEs. when i am calling from one phone to other phone i am getting the ring but i am not able to here my voice…….?????? what may be the proble.
    These CPEs are having RJ11 port…..

  2. dreamforccie says:

    Yes, it does! If you have such requirement simply try the method you have just mentioned. Additionally please follow the link below:

  3. Jaga says:

    Thanks Mijanur for your contribution. How about using voice class codec template with G711u and g729r8 on the dialpeer instead of hardcoding G711u on it? Does the Dialpeer select the right codec based on the incoming traffic? (G711u for MOH and G729r8 for RTP traffic/)

  4. Pingback: 640-460 Study Materials | voip equipment blog

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