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New Member

Call Failed @ Wireless IP Phone CP7921

I have to implement for a new WLAN setup for maily Wireless Voice & Data, and the provided Cisco WLAN components are as follows:-

1. WLC4404 & 4402, 1nos each --- 4402 is installed now.
2. AIR-LAP1242AG-N-K9 - 120 Nos. with AIR-ANT5959 120 Nos. ---- Testing with a single AP
3. CP-7921G-A-K9 ( Wireless IP Phone ) - 150 Nos. ---- Testing with 2 nos. Wireless IP phone
4. WCS ( 100+50) License ---- Not installed now
5. ACS - CSACS-1120-K9 - 1no. --- Not installed now
6. Call Manager - Version 7.1 - PUB & SUB both are installed and configured now
7. Cisco 7940 ( Wired IP Phone ) - 450 Nos. --- 4 Nos are installed and Wires IP phones are working properly.

I have configure WLC 4404 as below:-

Service Port :-
Managerment :-
AP-Manager :-
Virtual Gateway :-

Both Management & AP Manager with DHCP Server -, a Windows 2008

Cisco LAP 1242 - IP address on

Voice VLAN ( ALL Wired & Wiressless IP phone )

The Problem:-

The wires Phones are working properly with all required feature like call divert, perk, conf, fwd etc., but Wireless IP phones are getting erros like Call failed. They are getting IP address, & registering properly with Call manager details, TFTP etc, calls are coming / going to other extn ( Wired & Wireless Both ) but when trying to pickup, Wirelss IP Phone getting error call failed.

I have tested the a Laptop getting the same IP, in which the IP phones are connected, the laptop is working fine with all application.

Please help me and suggest me what could be the problem.

My Observation:-

Wired Phones are getting DHCP ip address like, but the Wireless Phones are getting DHCP as, rest all other configuration is getting perfectly fine compare to Wired phone.

Everyone's tags (7)

Re: Call Failed @ Wireless IP Phone CP7921

The DHCP server is not abnormal, that would correlate to the Virtual IP of the controller.

the first 3 things I'd check are as follows (especially since I just went thru this in the lab):

Item #1: make sure CAC is configured under the Radios..  Wireless> 802.11b/g/n & 802.11a/n

Item #2: Make sure the SSID for voice is set to platinum

Item #3: make sure 12mbps data rate is set to either supported or mandatory, I have seen an issue where this was set to disabled and I couldn't make calls.

try these things... Hope it helps

Please rate useful posts.


New Member

Re: Call Failed @ Wireless IP Phone CP7921

Hi Kayle,

I have done as per your advice, but no result as such.

Sending you the WLC config in text file. The Radio CAC configuration is not there in WLC....but somewhere else....send you the snap shpt as well, you can find the entire WLC config in the text file.

Waiting for your valuable advice, Thanks in Advance...!!!!!!!



Re: Call Failed @ Wireless IP Phone CP7921

WMM must be enabled in the Voice SSID where the 7921G will work.

Disable 7920 ap cac and client cac, You do not need these features for thsi phone.

I highly recommend this deployment guide (7921G deployment guide) to guide you to configure your WLC.

Also, your APS and phone are not for the same regulatory domain, if you configure your WLC like guide says and if the phone is still disconnected, please make a debug client to see what can be happening. WLC by default has 802.11d world mode enabled; it may not be the problem.

Best regards.

Re: Call Failed @ Wireless IP Phone CP7921

technically the AP's and Phones are not the same regulatory domain, but they are both America's although the -N domain is for non-FCC North America.. so I wouldn't think this would be an issue since they are both still americas and it's connecting it's just not getting the bandwidth to make a call.

Re: Call Failed @ Wireless IP Phone CP7921

In the CAC screen shot you sent; the 7920 settings should be disabled and WMM should be enabled..  The CAC I was referring to is under the Wireless Tab at the top, then on the left hand side you'll see a header that says 802.11a/n  and one that says 802.11b/g/n   if you expand those you will see many more options like Network, RF Grouping, Etc...

Depending on the version of code on the controller there will either be a voice category or a Media Category which will then display a page that has the following on it.

Call Admission Control (CAC)
Admission Control (ACM) Enabled
Load-based CAC Enabled
Max RF Bandwidth (5-85)(%)
Reserved Roaming Bandwidth (0-25)(%)
Expedited bandwidth

As the other poster indicated this is all in the 7921G Deployment Guide.

See if that helps.