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CUCM 7.1.5 and 7921 Wireless Phones

We have been struggling with problems with our wireless phones for months.  We are a healthcare facility and users rely on the devices and they are beginning to lose faith.  We have taken one area that we had continuous reports from, replaced most of the phones, increased our wireless coverage and it appeared to be better for couple of weeks and now we're back to having problems.  Calls aren't ringing to the devices, they are forwarding to the extension specified for "forward no answer," calls are cutting out and disconnection.  I just don't know what to look at next ... any thoughts?


Cisco Employee

Re: CUCM 7.1.5 and 7921 Wireless Phones

dnmosier7 wrote:

Calls aren't ringing to the devices, they are forwarding to the extension specified for "forward no answer," calls are cutting out and disconnection.

Detailed CallManager traces will show the call attempting to ring the wireless phone, since SCCP is TCP we should see the SCCP messages to start ringing the phone in the logs and those should be received by the phone again since it's TCP.  Since it's going to the CFNA (Call Forward No Answer) number call manager must think the phone has been ringing for a while and no one answered.  If calls are cutting out meaning audio stops while on the call that indicates a network/wireless issue.  The RTP stream is UDP from the calling device (gateway for PSTN calls) directly to the phone.  Depending on how calls are disconnected that will show up in the traces, one side is likely hanging  up, possibly because they can't hear the other person.  Here's how to turn on and collect traces if you're not familiar with it:

VIP Super Bronze

Re: CUCM 7.1.5 and 7921 Wireless Phones

I've been where you are with a few customers; it can get ugly. We cleaned them all up for the record.

The short answer is your problem probably isn't with the phones (assuming you have the most recent firmware on it), it's with the wireless infrastructure. The AP/WLC firmware has a lot of bugs related to voice and coverage is really touchy with VoWLAN. Our customers are camped out on the last few releases of 6.0. Anything before that is trouble and we're seeing indications of bugs being reintroduced in the new 7.0 code.

Calls aren't ringing to the devices, they are forwarding to the extension specified for "forward no answer,"

Try enabling the Out-of-Range Alert setting on the phone in UCM. Ask the user to tell you if their phone beeps at them. I would bet the phone is loosing coverage but not long enough for the heartbeat timers to make the phone unregister.

calls are cutting out and disconnection

What direction is cutting out: downstream to the phone or upstream to the AP? If both, does one happen more in specific areas? You can take a phone and put it in survey mode to see what you have for an RSSI. Look at the client history on the WLC to see how clear the phone has been seen.

Also in healthcare you have to be real aware of your surroundings. Any lead-lined walls nearby? Ultrasonic equipment? Anything that may be causing multi-pathing? 802.11 is unlicensed and some stuff can mess with it.

I rarely say this but send me an email if you're stuck and want a partner to work; my email address in in my profile. It's too complex for an answer to fit on a forum thread. We've cleaned this mess up before; not overnight but we've done it. We have several smart wireless engineers (not me, I'm the dumb voice guy ) who appear to have memorized the VoWLAN SRND.

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