Some Phones Can NOT hear each other

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Jan 3rd, 2009
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Dear All,

We are using Clustered CUCM 5.1 and suddenly new problem happen which is when making a local call from some phones the users cant here each other!!

What could be the problem??

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Jaime Valencia Sun, 01/04/2009 - 18:01
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routing issues, the RTP stream from one endpoint does not know the way or goes other way.

check the routing between the endpoints

since you can place the call apparently there's only routing between CUCM and phones.



if this helps, please rate

Nicholas Matthews Sun, 01/04/2009 - 18:12
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There is a very easy way to test this for routing issues (which is about 85% of one-way audio problems):

Find the IP address of the phone you're using, and go to the webpage of that IP address. Place a call, and keep it up.

On the phone's webpage, look at the network settings and get the default gateway. Then, go to the 'Stream 1' page. It should list a connected IP address where it is sending RTP to. As well, look at the 'Received packets' and see if the packets are getting to the phone or not. This helps determine whether you are getting blank audio or no RTP packets.

On the voice gateway, issue 'show call active voice brief'. You should see a line with the IP address of the phone you're testing if the call is still up. Try to ping this address, and check your routing tables. If you have multiple interfaces on your gateway, you will want to use a bind command to prevent the gateway from doing asymmetrical routing.


Interface level: h323-gateway voip bind


voice service voip


bind all source


Global config: mgcp bind media interface <>

You could also have bad DSPs, but you can't tell that without figuring out possible routing issues first.

Check to make sure that the routing in your network has not changed, as sometimes routing protocols change and voice traffic will then be sent through a new path which includes a firewall.

Figure out who can hear who, and then troubleshoot the routing from the originator of the traffic that is not being heard.



eemara949 Mon, 01/12/2009 - 00:20
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I am talking only on a local calls that dont touch the VOIP gateway and only access the CUCM.

kindly advice.

Nicholas Matthews Mon, 01/12/2009 - 04:38
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Go to the IP phone's webpages when the calls are up.

Check to see if they are both Rx packets. If one is not, start checking connectivity at the default gateway of the far end phone.



jbarcena Mon, 01/05/2009 - 10:42
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While having the problem take a "show voip rtp connections" on the GW that is making the call to see which IP Addresses are being used and verify the IP connectivity between those IP's


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