Voice call dropping

Unanswered Question
Oct 18th, 2007

Dear all,

We have voIP between two sites, connected over MPLS and voice calls drop now and then. We use Avaya for Voice boxes and Cisco routers/switches elsewhere. QoS is configured on both ends of the MPLS to prioritize voice packets and I do not see any drops in the voice packets at both the ends under "sh policy-map interface" command.

I am new to Voice and wondering where to start the troubleshooting.

Any help is appreciated.

Thank you,


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mmunoz-20 Fri, 10/19/2007 - 10:37


You will need to check first the codec configured in the dial-peers voip (Commonly G.729),

then check if you have configured the qos command in each dial-peer to mark voice packets.

ip qos dscp csX media

ip qos dscp csX signaling


ip precedence X (On earlier versions)

(where X is the Class of Service 3 or 5 depending on your MPLS Service Provider).

If you Voice Gateway is behind of your MPLS Router, you must be to configure a Policy-map in the Interface connected to the segment to identify and mark voice packets if this packet are not marked previously (service policy input XXX command).

Check in the output policy-map the command "priority XX" for the voice class (This ensure voice packets to go at priority queue).

And the last verify is the fragmentation in the output interface only if you use Frame Relay....


pranabgaya Fri, 10/26/2007 - 22:03

can u add "voice rtp send-recv" and "voice call send-alert" in global config .

is it call dropping in mid of conversation? also check for codecs in dial-peer at both ends.

appreciate if u attach the running config.



vinay_verma80 Tue, 01/01/2008 - 22:40


Plz send the debug for the connection b/w the pbx and router , so that we can find what is the cause of call disconnect

also plz again check that ur packets are being marked and the counter is increasing in the show policy map ( Ping will the 100 or more packets )

also give us the sh interface result and running configuration



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