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New Member

Occasional poor voice quality

Hi all,

I have preaty straight congig – LAN --- CCM --- H.323 --- PSTN. CCM is 4.1(2), gateway is 1760 with 12.3(11)T7, connection to PSTN is with three VIC2-2BRI.

Occasionally PSTN side hears “static” distortions or can’t here anything (one-way voice) for both incoming and outgoing calls. When call is closed and same number is immediately redialed there are no problems in conversation.

All this problems happen on different BRI ports, so I don’t think this is a telecom problem.

All counters form show interfaces, show controllers bri, show controllers voice don’t display any errors.

Any ideas for debug would be appreciated.


Re: Occasional poor voice quality

Do you have QoS configured?


New Member

Re: Occasional poor voice quality

No QoS on Fa0/0 interface.

Re: Occasional poor voice quality

What about on your switches?


Hall of Fame Super Silver

Re: Occasional poor voice quality

You definitely need to implement QoS on your switches, what type of switches are you using?

Depending on the switch model you might need to re-map cos-dscp and dscp-cos, so that voice queue is the expedite queue, and add the priority-queue out command on all switchports where phones are connected. Here is a good link for 3550, obviously it's different for all Cisco switch models.


Re: Occasional poor voice quality

Along with the QoS recommendations by others, when the one way audio happens is it for the entire call (start to finish) or just parts? When this happens if you can keep the problem call up, can you ping between the phone and the gateway fine? ping the phone on the router using the interface the router is sourcing voice traffic from.

If the one-way audio is for the whole call, then it may be another issue where the audio is not working at all for some reason or the audio wasn't cut over right. If you look at the IP phones web page on the problem call under the stream page, is the remote IP address correct (should be gateways IP address on external call).

What version phoneload on the phones?

New Member

Re: Occasional poor voice quality

Hi again,

Sorry for late response. Phones firmware is as follows:

7912 - CP7912060101SCCP050429B

7940 - P0030702200

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