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PoE+ on 3750x - Phone Keeps Rebooting?

Hello

We have a Cisco IP phone which keeps rebooting and re-registering itself as a result.

The CDP neighbour information shows the phone is Class 4 PoE drawing 17.7w and its plugged into a Single (non stacked) 3750x Switch with a single

C3KX-PWR-715WAC power supply.

Now reading some Cisco documentation, it seems to suggest we need at least 1440w of total power to successfully power anything which requires more than the standatd 15.4w of power?

From the Cisco Website......

Q. Do I need two power supplies on the Cisco Catalyst 3750-X and 3560-X Series PoE switches to deploy PoE+ (802.3at)/UPOE?

A. The requirement for PoE+ is 1440W for a 48-port switch or 720W for a  24-port switch, in addition to the system power requirements, which  include the reserved power needed to power up the Cisco StackPower stack  during formation. This requirement already exceeds the rating of any  available power supply; therefore, a second power supply would be needed  unless the switch is part of a Cisco StackPower stack and the system  can provide the remaining power required.
Does this mean we have to have 1440w to even run a single PoE+ device?
Cheers
6 REPLIES
Hall of Fame Super Gold

PoE+ on 3750x - Phone Keeps Rebooting?

We have a Cisco IP phone which keeps rebooting and re-registering itself as a result.

Only ONE phone?  Could be a cable issue.   Do this:

1.  Command:  test cable tdr interface ;

2.  Wait for approximately 5 to 7 seconds;

3.  Command:  sh cable tdr interface ; and

4.  Post the output to #3.

PoE+ on 3750x - Phone Keeps Rebooting?

This is the only phone we have on this site which needs power above the 15.4w standard and its the only phone on that particular which but no others are rebooting onsite.

Tried that and got this, I waited 20 seconds?

Interface Speed Local pair Pair length        Remote pair Pair status

--------- ----- ---------- ------------------ ----------- --------------------

Gi1/0/22  1000M Pair A     N/A                N/A         Not Completed

                Pair B     N/A                N/A         Not Completed

                Pair C     N/A                N/A         Not Completed

                Pair D     N/A                N/A         Not Completed

Thanks

Hall of Fame Super Gold

PoE+ on 3750x - Phone Keeps Rebooting?

"Not Completed"????

Try again, wait for about 10 seconds this time.

Otherwise, change the patch cable nearest the switch.

PoE+ on 3750x - Phone Keeps Rebooting?

Tried again and waited a minute, same result!

Tried on another active port which is connected to a Cisco AP and the same Not connected

Odd...

Hall of Fame Super Gold

PoE+ on 3750x - Phone Keeps Rebooting?

Replace the patch cable nearest the switch and observe if the behaviour is replicated.

PoE+ on 3750x - Phone Keeps Rebooting?

Ahhh it actually turns out the phone is not rebooting, it keeps re-registering itself every 15 minutes or so.

The phone is sitting there happy and then all of a sudden, the display shows only the words 'Phone not registered', then it goes back to the normal screen.

I know the phones do register themselves as a preconfigured interval, I thought this was transparent to the user of the phone and the display should not be showing anything?

Its a 9971.

Thanks

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