intermittant oneway audio on offnet calls

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Dec 3rd, 2008
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We have a CCM 4.2. WE are experiencing intermittant oneway audio on offnet calls. Weare going out a Cisco 2851 and 3845 gateway. All the reported incidents report that IP side can not be heard out to PSTN called party.Both gateways are using PVDM2-64 SIMMs. Any ideas what is causing this intermittant problem

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carenas123 Tue, 12/09/2008 - 09:03
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Here is the some troubleshooting steps it may help you

Ensure That IP Routing Is Enabled on the Cisco IOS Gateway and Routers

Check Basic IP Reachability

Verify Correct Media Termination Point Configuration

Bind the H.323 Signaling to a Specific IP Address on the Cisco IOS Gateway and Routers

Bind the MGCP Signaling to the MGCP Media Packet Source Interface on the Cisco IOS Gateway

allan.thomas Tue, 12/09/2008 - 12:05
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As you have two voice gateways, the first aspect to investigate is which of these gateways is possibly causing the one-way audio?

Are both gateways being used for all outbound calls? Or is each gateway using separate carriers for different billing purposes?

Determining which gateway the outbound call is established through will help to isolate the problem.

As the problem is intermittant I suspect that it is only calls which are established over the gateway which is possibly the second gateway within the route-list when all channel on first gateway are busy?

As the previous post suggested, ensure that the IP address used for signalling on either gateway whether it is H323 or MGCP is reachable from all respective voice VLANs.

Hope this helps.


edison_abad Thu, 12/11/2008 - 23:31
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we had experienced intermittent one way audio problem before and here are some recommendations:

- possible that your phone and your VG are registered to different call manager. try to register them on one Callmanager only and observe.

- make sure that there is no errors on the switch ports where ur CMs are connected. if your using a 1Gps switch, cisco recommends to set ur port as auto/auto. if 100M, set the port to 100/Full.


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