7912 Phones Screen On but No Dial Tone

[jgoo]

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

[jgoo]

I checked on the phones.  Most of them are actually set to connect to Sub first (which is what they are doing, even in the error state).

We do have a range of phone types on our network.  But the problem seems to be limited to the 7912s and some ATA 186 Analog converters.  The newer phones, like 7841, seem to be fine.

The requested utils results are attached for both pub & sub.

I also ran an unregistered phone report using the RTMT (attached), but when I went through the report, I noticed that phones in this state aren't necessarily showing up.   For example, I know x3838 is currently in this state (the CUCM GUI shows it's Status: None and IP Address: None - though I know that it's online with IP address 10.11.0.239), but that extension isn't listed in the report.

I really appreciate the troubleshooting assistance!

[Evgeny Izetov]

By default Unregistered turns into Unknown in 3 days and then they won't show up in unregistered phone report:

https://supportforums.cisco.com/discussion/10717281/cucm-6x-ip-phone-status-values#1069035

It's interesting that we see are lot of 7912 with DeviceInitiatedReset and they were all registered to Pub and then starting at 10am they apparently failed over back to Sub. The question to ask would be why they were registered to Pub in the first place if they should always be registered with Sub (according to their CM Group)?

Found this excellent blog post:

http://blog.qsolved.com/2014/03/how-does-cucm-ip-phone-keepalive-works.html

[jgoo]

Yeah.  One of the things that we looked to see was if the phones were registered to the wrong call manager, and that was causing it.   But I just double checked.   We have 1 extension x3810, which is currently in the "no dial tone" state.   I went to it's web page, and checked.  Call Manager 1 is showing as the Sub (10.11.0.11), as expected from how the phone is configured.  So even though it's trying to connect to the correct node, it's still experiences the problem.

[Robert Maule]

Justin,

Have you been able to find out the reason for your phones unregistering?  I am having the same exact issue.

I am on a college campus and our 7912s will periodically unregister with sub1 and they appear to be working until you pick up the handset and there is no dial tone.  It could take days or weeks or months.  In CUCM, they are marked as Unregistered or None (if over 3 days).  Unable to web into their IP addresses, though.  The StatusReason in RTMT shows DirectoryNumberMismatch, which seems to indicate a SIP issue from my research, even though they are SCCP phones.  There are no duplicates of the DNs that I can see.

CUCM System version: 10.5.2.10000-5, as well, and version 8.0.4 for the firmware on the phones.

[jgoo]

Nope.  No answers yet I'm afraid.  At least I'm not the only one out here with that weird issue.