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7921g and wlc 4404 oneway voice problem

fabriziop
Level 1
Level 1

Hi,

I have a metwork with 35 AP 1242 (only 2.4ghz band) and 30 7921g.

I'm using a WLC 4404 version 4.2.61 7921G version 1.1.1, CCME version 4.1, AP IOS 123-7JX.

The coverage seems to be good and also the overlap.

The problem is: some times casually and also not walking we lost voice (one way o both way) for 10 or more seconds the call is still active. I tried to improve roaming, I have enable WMM support, DTCP and all the features racomanded on the wlc docs. I have analised RF interfernce with wy-spy and not seems to be relevant interference. The AP profiles are all in pass (if you check on the WLC) I can ping the CCME with a PC on the WiFi VoiceVLAN.

It very stange and a can't find a solution because the problem is not localised in an area. It is more evident when we have a conversation between 2 wifi phones.

I can't find a way to solve the problem.

Thanks

31 Replies 31

I am having the same problem. CCME 4.1

WLC-4402 1100 seires ap. Your problem sounds

indentical to mine. I worked TAC we have yet

to find a resolution.

Did you verify the QoS setting on the switch port the LAP is connected to, the trunks on the switch and the port channel the WLC is on.

-Scott
*** Please rate helpful posts ***

How should the ports be setup?

AP ports should be mls qos trust dscp

WLC Port Channel should be mls qos trust cos (or dscp... i use cos)

Switch to Switch trunk ports should be mls qos trust dscp.

Here is a deployment guide for the 7921 which explainse the WLAN settings also.

http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/7921g/6_0/english/deployment/guide/7921dply.pdf

-Scott
*** Please rate helpful posts ***

How should the ports be setup?

disregard the last post thanks I am looking into the qos.

qos is correct still having the same problem.

migilles
Cisco Employee
Cisco Employee

If the issue is between 2 7921, ensure that P2P blocking (PSPF) is not enabled on the WLC, otherwise will always get no way audio between 2 wireless phones.

What is the current firmware of the 7921?

We released 1.2(1) a little while back and would suggest to use that version.

There was an issue a while back where if it got deauthenticated using WEP (believe version 1.0(4)), it could lead to a 10 second voice gap. I also would recommend to use 4.2.130.0 or even better 5.1.151.0, which has TCLAS support and will use port info vs DSCP to put the packets into the correct queues.

Not sure if you are doing layer 3 roaming or not, but if so, enable symmetric tunneling.

Since it's a long gap, I wouldn't be so quick to point to RF here.

I would suggest trying open authentication and see if you can reproduce it. If so, what triggered it, roaming event, etc.

Capture the wlan sniffer trace and can then see what's happening. Cisco TAC should be able to help you there.

See the 7921G Deployment Guide for more info.

http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/7921g/6_0/english/deployment/guide/7921dply.pdf

This sounds like a near far issue, if there are no interference sources around Use the following list to identify possible causes for the problem:

•Check the access point to see that the transmit power setting matches the transmit power setting on the phone. One-way audio is common when the access point power setting is greater (100mW) than that of the phone (20mW).

Cisco Unified Wireless IP Phone 7921G Firmware supports dynamic transmit power control (DTPC). The phone uses the transmit power that the access point advertises upon association.

--------------------------------------------------------------------------------

Note With DTCP, if Client Transmit Power is set in the access point, the phone automatically uses the same client power setting. If the access point is set for the maximum setting (Max), the access point uses the Transmit Power setting on the phone.

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•Check that the access point is enabled for ARP caching. When the Cisco Unified Wireless IP Phone 7921G is in power save mode or scanning, the access point can respond to the wireless IP phone only when ARP caching is enabled.

See the "Voice Over IP Wireless Network Configuration" section on page 2-28 for more information.

•Check your gateway and IP routing for voice problems.

•Check if a firewall or NAT is in the path of the RTP packets. If so, you can use Cisco IOS and PIXNAT to modify the connections so that two-way audio is possible.

•Check that the Data Rate setting for the phone and the access point are the same. These settings should match or the phone should be set for Auto.

•Check the phone hardware to be sure the speaker is functioning properly.

•Check the volume settings in the Phone Settings menu.

Hi thanks all for you support.

I can't understand how to proceed: the problem is Qos? WLC configuration?

The DTCP is enabled, with ping on the VLAN wifii can reach the CCME, no nat or firewall, hardware ok,WMM is on, platinum Qos is enabled on the voice SSID

Now I will check the datarate, and how can enable ARP caching?

Now I'mstaring the TAC.

Before you raise a TAC case tell us what the power setting is for the AP and the antenna

I don't complitely understand your question but, I'm using full tx power by derault on the wlc auto power RF in global management and as anttenna the 2.2dBi rubberduck and four outdoor the 5.2 dBi omni dipole.

As you are using full power the ap is transmitting at 100mW. The 7921 only transmitts at 20mW. Is the on way voice that you hear to the phone or from the phone. Turn the power down so the max tX on the WLC is 10mW. 10mW is 10dBm + 2.2dBm from the antenna is about 17mW. then tha AP and the 7921 will always hear each other

I have enable ccx extensions.

One way spech is not so frequent, the frequent problem is that I can't hear the voice in both ways. The comunication is still up and i'm not walking.

But I will check the power setup.

Thanks

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