RTP traffic from phone go to call-manager not to other phone

Unanswered Question
Apr 12th, 2010
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hello everbody,

     i have a CCM with cisco phones registered to it and call established and voice is very clear, also i have another central "Nortel" with nortel phones registered and everything is ok.

i have configured SIP trunk bet the call manager and the nortel central.

when i call from cisco to nortel or vise versa:

1-call established easily.

2-two way voice reachable "both ends can hear each other" BUT WITH VERY BAD Quality.

hints: a-call statics: jitter 700-900 "too high", packet dropped

         b-both phones exist in  the same vlan "in the same switch",,belive me no QOS or routing or rate limit issues, i tested it deeply.

when we checked the logs at nortel central we found; the RTP traffic end point is "Cisco Call Manger IP"???? not the other phone ip!!!

but i can't find anything strange in the Call manager configuration it is a systimatic and i don't use any special services, just intiate the call.

please help in resolving this issue as the VOIP connection between these 2 networks are needed urgently.

thanks colleagues for your help and your time.


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Jaime Valencia Mon, 04/12/2010 - 07:59
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If you're using an MTP that would explain why you see that call flow.

If you don't neet to put the call on hold, transfer or conference try unchecking the MTP option in the SIP trunk.

On the Cisco ip phone press ? or i twice and you'll see call statistics real time, if you see jitter or delay i'd suggest to recheck the RTP path for QoS or congestion.



If this helps, please rate


Aaron Harrison Mon, 04/12/2010 - 07:59
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Your RTP is being routed via a Media Termination Point (part of the IP Voice Media Streaming service on the CallManagers). It will do this if you check the 'require MTP' box on the trunk page, or if CCM believes it needs the MTP. Try unchecking that option and see if you still have full functionality (i.e. things like hold and transfers or forwards work).

If you need an MTP you could configure a local gateway on the site with the phones and Nortel as a transcoder in order to keep the traffic local...



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