7921 - Sound problems during IP phone to IP Phone call

[cpartsenidis]

Hello everyone,

I've just installed a number of 7921 IP Phones at a customer with multiple sites. Each site has a Cisco Call Manager Express running IOS 12.4.15T (Supports 7921) on 2811 and 2801 routers.

The problem I am experiencing is that once the 7921's are online, the first call they make to any IP phone works correctly. From there on, for 70% of the calls made between IP Phones, I can't hear anything from the 7921's earpiece as there is no sounding coming from it!

If the 7921 makes an external call e.g I might call home or my mobile phone, everything works fine and you can hear the other side without a problem. The problem seems to be present only when talking with another IP Phone (any type of ip phone) on the network.

I've checked the firmware on the 7921's and they are the latest (1.0.4), and upgraded the Call Manager Express IOS to at least 12.4.15T which supports the phones (according to Cisco).

The access points used at headquaters are 1100 series and the remote sites have 876W routers which also act as access points for the 7921's.

All sites have WEP enabled (128bit) and MAC address access lists with SSID broadcast blocked.

Any suggestions or ideas are welcome and much appreciated.

Thank you.

[mheusing · Accepted solution]

Hi,

what is the usage of wireless during the "trouble call"? Are both sides experiencing the same issue, i.e. no sound, if the call is between two 7921? Are both telephones pingable during the time the issue shows? Is voip traffic arriving at the phone or is it a transport issue?

Regards, Martin

Regards, Martin

[cpartsenidis]

After checking if I was able to ping the ip phone, I discovered that the problem was at the access point where I had placed mac-address based access lists.

More specifically, under the interface Dot11Radio0.1 removing the following entry resolved my issue:

bridge-group 1 output-address-list 700

Thanks very much for your help.

Chris Partsenidis

www.Firewall.cx

[p.curtis]

Hi Martin,

I have the same issue between 7921 phones. The call setup between two 7921s is fine but there is no sound.

Phones are pingable.

On the Call Statistics screen I see Sender Packets counting up, but Rcvr Packets is zero.

Calls out to PSTN and to other CCM clusters are fine, so it looks like a wireless problem.

There are no access-lists configured on my access points.

Is there any setting that prevents direct client to client wireless communication?

Rgds, Phil.

[cpartsenidis]

Could it be possibly a firmware issue ?

The IP Phones I was using are loaded with firmware 1.0.4.

Cheers,

[p.curtis]

Hello Everyone...

Calls between 7921G phones are now working okay.

There was a parameter within the Wireless LAN Controller that blocks peer to peer communications by default.

In the Wireless Lan Controller GUI, in the Controller TAB the option is Peer to Peer Blocking Mode and it needs to be Disabled before the audio path between 7921 phones can be heard.

Hope this helps anyone who had the same issues as I did!

Rgds,

Phil.

[migilles]

This is disabled by default.

Will prevent 2 clients from communicating to each other directly. This is a global command and PSPF can not be enabled on vlan or ssid level like with the autonomous APs.

[dennischolmes]

This also assists with issues around CALEA guys. Take note.

[migilles]

Would ensure ARP requests are getting responded to.

Would refer to the 7921G Design Guide for more info @ http://www.cisco.com/univercd/cc/td/doc/product/voice/c_ipphon/english/wip7921/7921dply.pdf.

[meggerman]

I have the DTPC enabled but still get this delay, the plot thickens as its intermitent and now some phones although running the same everything are not experiencing it ? one phone had ch 11 on the survey aswell as ch6 ? i didnt specify it, only ch11 should have been on there, and yet that works the best.

are there any other auto settings, or tweaks a 7921g would require over a 7920g on the WLC,AP etc.. ?

many thanks

[migilles]

See the design guide @ http://www.cisco.com/univercd/cc/td/doc/product/voice/c_ipphon/english/wip7921/7921dply.pdf.

[spiecomcisco]

Hello, i 've the same problem between 7920G phones. I can't communicate (audio) between 2 7920 phones : the comuunication is established but i have no sound. I can communicate with a 7920 and others ip phones. My phones and my ccm6 are on the same subnet and the same vlan. Any idea?

On my ap, the native vlan is the voice vlan. Can it make a problem? If yes, should i have to configure a specific vlan for voice and an other for the native vlan? the problem is that my voice vlan (and so native vlan) is the VLAN 1 on my aps and on all my switchs. If i must change my voice vlan, i must change the vlan on my switch too. Must the native vlan be propagate on the others switchs?

thanks

[migilles]

Well since this original topic was opened for 7921 and CME environment, you should open a new thread.

With that said, should ensure that the 7920s are running version 3.02 and the APs are running 12.3(8)JEA2 or higher.

Ideally, the native vlan should be the data vlan or a vlan dedicated for IAPP and recommend that VLAN not be VLAN 1.

Ensure you have ARP-caching enabled (dot11 arp-cache optional).

Also ensure the at PSPF (peer to peer blocking) is not enabled, otherwise 2 7920s on the same AP will not be able to pass data to each other successfully.

You can attach your AP config for further analysis if you like.

[spiecomcisco]

In fact it was my ap config. My native vlan was the same that the voice vlan. In separating native and voice vlan it works better.

Thanks for help