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Highlighted
Beginner

7912 Phones Screen On but No Dial Tone

Hi all,

I know that the Cisco 7912 phones are older phones, but we have about 200+ of them on campus, and they have been giving me a lot of issues lately.   Specifically we have been having an error with the phones where:

  • The phone screen remains lit and showing correct information as normal.
  • You cannot call the phone.
  • When you pick up the phone, it has no dial tone.
  • When you unplug everything (PoE network) and reboot the phone it comes back fine.

This has been happening repeatedly to multiple phones across campus.   We have tried to isolate it as a network issue, but our network consultant assures us our network is fine.    Our phones are on the latest firmware available for that model.

Any troubleshooting assistance would be greatly appreciated!!

Thanks,

Justin

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19 REPLIES 19
Highlighted
Cisco Employee

Hi Justin,

Hi Justin,

Since, you are not even getting a dialtone, the CUCM connectivity to phone is certainly lost as CUCM sends a signal in a SCCP message to play that dialtone.

I would recommend that when the issue crops up, collect a set of capture from back of the phone and you should be able to see some sort of packet re transmissions between the CUCM and the phone.

Refer following docs, if not familiar with collecting captures from phone and CUCM server:

https://supportforums.cisco.com/document/44376/packet-capture-cucm-appliance-model

https://supportforums.cisco.com/document/44741/collecting-packet-capture-cisco-ip-phone

Regards,

Hitesh

Highlighted
Beginner

I will give it a try the next

I will give it a try the next time it happens.  Thanks!

Highlighted
Beginner

Wait.   I just tried looking

Wait.   I just tried looking for the "span to PC" instructions for the 7912 model phones.  But it says that the 7912 phones don't have that feature.  So I don't think I will be able to do the packet capture.   

Highlighted
Cisco Employee

Since 7912 phones do not have

Since 7912 phones do not have that option, your best bet then is to collect captures from the switch itself using port mirroring.

Regards,

Hitesh

Highlighted
Beginner

Hi Hitesh,

Hi Hitesh,

I was finally able to mirror a port with one of the phones in the "no dial tone" state.    I've attached the wireshark trace.   10.11.1.27 is the phone and 10.11.0.10 is our call manager.   During the trace I picked up the handset (there was no dial tone) and tried calling a number.   This is all I got out of my trace.

Any suggestions?

Thanks,

Justin

Highlighted
Beginner

For the phone in question, I

For the phone in question, I checked the switchport and the phone shows up in the arp table.   I checked the DHCP server and the phone actually has an IP address, it's just not registered in the call manager.   I tried pinging the phone and looking at the phone's web interface, both work just fine.   

But when I pick up the handset and dial, the trace doesn't even show the phone sending an "OffHook" command.   What would  cause the phone to do this?   It is already on the latest firmware for a 7912 (ver 8.0.4).  

I can't figure out why the phone isn't sending the "OffHook" request or how to fix it.

Any ideas would be greatly appreciated.

Thanks,

Justin

Highlighted
Beginner

On the phone's web interface

On the phone's web interface what do you see in the Status Messages? Also, what version is the CUCM?

Highlighted
Beginner

Um... I don't see a status

Um... I don't see a status messages section.

Highlighted
Beginner

Just to clarify, are all 7912

Just to clarify, are all 7912 phones experiencing the issue, or only some of them?

When you say after power cycle the phone comes back fine, do you mean it registers and makes calls but then unregisters after a while?

Are the phones in 'no dial-tone state' showing as "Registered" or "Unregistered" in CUCM? In your original post you mentioned the phone display is normal when in 'no dial-tone' state, i.e. it shows extension and "Your current options". Does the phone show as 'Unregistered' in CUCM at that point (this would be unusual)?

What version of CUCM?

On the phone, hit Settings > Status > Status Messages. What messages do you see there?

On the phone's web interface, under Network Configuration, do all IP's look familiar? Does any of the 'Call Manager' say 'Active' next to them?

Can you reliably replicate the issue and collect packet capture as the phone is going into 'no dial-tone' state?

Highlighted
Beginner

The issue is happening

The issue is happening randomly to 7912 phones across campus.  We have 220 7912 phones.  When everyone came back from Winter break, I had about 20 of them with this issue.

After you power cycle, the phone registers and works.  But there have been phones who are repeat offenders, and others that aren't.

The phones show up as Unregistered in CUCM.   But yes, on some of the phones the OSD shows normal, on some it is missing some options but still lit.

We are using CUCM System version: 10.5.2.10000-5.

Under the network configuration all the IP addresses (the DHCP, DNS, Gateway, etc are all correct).   However, none of the Call Managers show as "Active" (there is 1 Passive and 1 with nothing next to it).

I cannot reliably replicate the issue.   It just happens randomly to phones.  People come in and pick up their handset and notice that there is no dialtone.  After they reboot there are 5 voicemails waiting, so they don't know how long the phone as been offline.

Highlighted
Beginner

Are the phones always

Are the phones always registering with the CUCM node that is listed first in their Device Pool's 'CUCM Group', or do you see them registering with the node listed second (or third)?

Highlighted
Beginner

I have seen them registering

I have seen them registering to both servers.

Highlighted
Beginner

When I looked at the status

When I looked at the status messages on the phone itself, all I see is the cnf.xml.

Highlighted
Beginner

Please confirm that the

Please confirm that the phones are always registering with the server listed first in their CUCM Group. Some phones may be assigned a different device pool, so it's ok for some phones to register to one node, and some to another, as long as that's the first node in their Device Pool's CUCM Group. If they register to a second node and don't re-register to the first node even after reset or power cycle, then that's an indication of a problem.

Forgot to ask, do you have other phone models in the cluster? Any issues with them?

Please run the following on CUCM Publisher:

utils ntp status

utils dbreplication runtimestate

utils diagnose test

Run the following on CUCM Subscriber:

utils ntp status

utils diagnose test

Keep an eye on 7912's in CUCM web gui and if you see any with a status of Unregistered, use RTMT to run unregistered phone report:

https://supportforums.cisco.com/discussion/11161311/unregistered-phone-report

Note the StatusReason and TimeStamp. Collect CUCM traces starting a few minutes before the timestamp. Provide the StatusReason, the MAC of the phone and the timestamp.

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