7841 not aquiring DHCP

[mjwald3200]

We have a mix mostly of 7841 and 8811 phones.

In some areas the 7841 phones intermittently loose the network, (network unavailable)

You cannot even ping the phone.

If you factory reset the phone, it will never even acquire an IP address.

I can pull that phone out, and plug in a 8811 and it comes right up.

I can also take the 7841 phone down the hall and plug it in, and it comes right up.

But once a phone fails on a specific network switch, it will never work on that switch again, but will work on other switches.

Completely lost on this.

[seanvaid]

What version of cucm?

One thing I would look into is the firmware you're using for the phones.

[mjwald3200]

Sorry forgot to add that,

CUCM 10.5

Firmware on the 7841 phones was upgraded to hopefully fix this issue, it did not, is now at 11.7.1.17

[seanvaid]

Ok, you might have to call TAC on this one. It's tough to troubleshoot without having visibility on the network..

Does this seem relevant? https://bst.cloudapps.cisco.com/bugsearch/bug/CSCun23612

[mjwald3200]

That's very interesting, looks like it was fixed by 10.5, but worth a look.  No idea how much broadcast traffic there is.

[seanvaid]

Do you have a lab or test environment where you can isolate this? 

That might help. It might also be beneficial to better search the bugs for that model. 

[mjwald3200]

Ok, so this issue has never really gone away.  The 7841 simply does not acquire an IP address, rebooting the phone makes no difference, even resetting it to factory make no difference.  However, removing it from that area (putting it on a different switch), it will com up right away.  Also leaving it unplugged until the switch address forgets the MAC address also allows the phone to come back up.

Any thoughts?