New 8841 VoIPs intermittently dropping calls

[beseamans]

Installed New 8841 phones,  they intermittently drops calls,  At that time, display shows Detecting Network then phone is usable again.  This takes about  5 seconds

CUCM 11.5,

VoIP 8841 HW Version 42 with firmware 12.8.1 (Upgraded to Version 14.0.1, Same issue)

Older VoIP 8841 HW version 31 with firmware 12.0.1.11 works fine, no issues (Also upgraded to version 14.0.1,  still no issues)

It appears that 8841 phones that came with firmware 12.8.1 are the only ones having this issue.  When the phone drops the call, the display shows detecting Network.  The associated router provides DHCP for both versions,  

When 12.8.1 drops, the Phone appears to be requesting a new IP at that time,  even when Lease is set to infinite,  it doesn't matter.

[Nithin Eluvathingal]

If the phone is  showing Detecting Network, I feel like phone is loosing  network connectivity. How many phones are effected ?

Did you replacing the network cable ? DiD you check the connectivity ?

[beseamans]

The switch port never drops, all cisco 8841's with hardware ver42 using firmware 12.8.1 have this issue intermittently.
It also does it while phone is on-hook. When it goes to detecting network, I look at the router logs and at the exact time it happens,
the phone sends A DHCP release request and then goes through the whole DHCP process requesting and IP the re-registers with the CUCM takes a total of about 5 seconds for all this to happen.
Older cisco 8841 phones with hardware ver 31 and firmware 12.0.1.11 never have this issue.

[Nithin Eluvathingal]

Do you have a valid smartnet? , i would suggest  open a TAC case.