phones lost connection

[Austin3:16]

I've noticed that some IP phones, specifically the 3905 model, enter "configuring IP" mode. Upon diagnosing the issue, I observed that these IP phones lose their IP addresses from the DHCP server. Even when configured in static mode, the problem is temporarily resolved, but after a few days, the phones lose their IP addresses again. The phone in static mode also becomes unpingable. I performed an upgrade to the latest version, but the issue persists after a few days.

and I noticed some port instability on the switch.

[Leo Laohoo]

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@Austin3:16 wrote:
but after a few days, the phones lose their IP addresses again.

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How long is the DHCP lease?

[Austin3:16]

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@Leo Laohoo wrote:

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@Austin3:16 wrote:
but after a few days, the phones lose their IP addresses again.

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How long is the DHCP lease?

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8 days but the problem with static ip too

[Leo Laohoo]

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@Austin3:16 wrote:
8 days but the problem with static ip too

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Can you elaborate the meaning of "static IP"?  Did you manually assign an IP address to the phone or did you put a MAC address reservation against an IP address? 

Bring the lease down to 8 hours and see if it makes a difference.

[Maren Mahoney]

You note switch port instability. I can see that impacting the phones. I assume you are taking steps to diagnose and resolve that issue.

Do the phones come back if you power-cycle the port?

Maren

[Austin3:16]

yes

[Carlo Poggiarelli · Accepted solution]

Hi,

I noticed this behavior in the past but it was not a DHCP issue. It was a bug with CDP messages received by the phone that was interpreted as port reconfiguration message.

Try to statically define the Voice Vlan on the phone and disable CDP on the switch interface.

Please let me know 

Regards

Carlo

[Austin3:16]

Ok i will let you know if the problem percist.

I have concerns about the Switches 2960  can upgrading the firmware resolve the issue since they have an old firmware 

[Austin3:16]

yes you are right and its solve my problem 

[Carlo Poggiarelli]

It depends on what model of 2960 you have.

Some of them went in EoL ages ago and firmware is no longer available on Cisco Software Manager.

Let me know 

Thanks

Carlo

[Austin3:16]

Yes know, they have E6 firmware i will try to E9 its the last version

[Carlo Poggiarelli]

before upgrading the firmware, please try what I suggested to verify if the issue solves with this configuration 

Thanks

Carlo

[Austin3:16]

 If I disable CDP, will there be any impact on Cisco access points?

[Carlo Poggiarelli]

Technically it doesn’t have any impact on AP but you don’t need to disable it globally but on single interface where 3905 are connected to.

Let me know 

Cheers

Carlo

[nathanhutchinson]

I have twice now had what sounds like the same issue, disabling CDP on the interface didn't fix and when I do a debug I don't see and CDP or DHCP data coming from into the interface from the phone, each time when I have replaced the phone with another of the same model, the new phone doesn't have any issues and comes up straight away. Leading me to believe that this would be a fault with the phone itself (hardware or software)