7841 IP phone power comsumption issue

[kljones84]

Hello,

My company has recently moved from the 7900 series IP phones to the 7800 series. More specifically the 7841 model. I've notice while deploying these phones that some will start the boot process and then all the sudden power down.

Looking on the switch I am seeing the log error message:

Sep  2 10:33:43: %ILPOWER-5-ILPOWER_MISCONFIG: Interface Fa6/18 is denied power as it requires more power than the configured maximum wattage(15400 mw).

User guide for the phone states that the phone uses no more than 3.4mw. Looking further into the switch the default 15.4mw per port is configured. See below:

sh power inline fa6/18 detail

Interface: Fa6/18

Inline Power Mode: auto

Operational status: on

Device Detected: yes

Device Type: Cisco IP Phone 7841

IEEE Class: 1

Discovery mechanism used/configured: Ieee and Cisco

Police: off

 

Power Allocated

 Admin Value: 15.4

Power drawn from the source: 4.2

Power available to the device: 3.7

 

Actual consumption

Measured at the port: 1.4

Maximum Power drawn by the device since powered on: 2.4

 

Absent Counter: 4

Over Current Counter: 0

Short Current Counter: 0

Invalid Signature Counter: 98216238

Power Denied Counter: 4

I've now had users phones power down after they were registered which of course causes lost of network. Receiving same error has above when i look on the switch. I am experiencing the issue at two separate sites where these phones are being deployed. 7900 series phones and 8831 conference work/worked with no issues on the network.

Any help or ideas would greatly be appreciated.

Thanks,

Kyle

[Aman Soi · Accepted solution]

Hi Kyle,

Just have a look into bug:

7841 phones fail to power up and boot fully when connected to 6500 PoE

CSCuw03106

Description

Symptom:
7841 phones will power on and begin booting and then turn off (no power).

Conditions:
Hardware version - V04 which can be identified by the phone's rear sticker (PID VID: CP-7841-K9 V04) or revision 33 seen from the phone's webpage. Occurs on firmware version 10.3.1-12 and has only been seen with the phone is connected to a 6500 switch using PoE.

Workaround:
On the 6500 switch ports, statically set the maximum power to 15.4 watts per port with "power inline static max 15400". The phone will boot up properly with 15.4 watts allowed on the switch port.

Further Problem Description:
The phone negotiates power class 1 with the switch. The phone then sends its first Cisco Discovery Protocol (CDP) to the switch with the power consumption value of 15400mW or 15.4 watts which exceeds the maximum of 3.84 watts allowed for power class 1 devices. The 6500 logs an inline power misconfig and denies power to the port causing the phone to shutdown.

*Aug 28 09:44:53.610: %ILPOWER-5-ILPOWER_MISCONFIG: Interface Gi3/1 is denied power as it requires more power than the configured maximum wattage(15400 mw).

regds,

aman

[kljones84]

Thank you sir.

Appreciate you taking the time to rely and opening my world to the bug search feature on the Cisco site. 

Kyle