How To Disable PoE feature on a individual switch port

[Mitesh Manwatkar]

Hi,

I have a PoE enabled device connected to our 2960-S switch port Gi 2/0/45 for which I am getting following log continuously.

184581: 045866: Jul 18 09:22:06.305 MUM: %ILPOWER-7-DETECT: Interface Gi2/0/45: Power Device detected: IEEE PD (D_USER_STACK-2-2)
184582: 045867: Jul 18 09:22:07.469 MUM: %ILPOWER-5-IEEE_DISCONNECT: Interface Gi2/0/45: PD removed (D_USER_STACK-2-2)
184583: Jul 18 09:22:08.513 MUM: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0/45, changed state to down
184584: Jul 18 09:22:09.530 MUM: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/45, changed state to down
184585: Jul 18 09:22:10.830 MUM: %PARSER-5-CFGLOG_LOGGEDCMD: User:mman  logged command:!exec: enable
184586: Jul 18 09:22:11.790 MUM: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/45, changed state to up
184587: Jul 18 09:22:12.791 MUM: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0/45, changed state to up

This is causing the port to flap continuously.

The device is working on the required ac power supply which can not be removed as device gets powered off completely.

So disabling the PoE capability on the port may solve the issue.

Kindly suggest the steps/commands or any other solution to solve this issue.

Regards.

[paul driver]

Hello

Int xx

power-inline never

Res Paul

[Mitesh Manwatkar]

Hi Paul,

I did what u suggested...and it has worked for me....the port flapping has stopped now.

For knowledge purpose can u explain what is exactly happening here...how does this PoE works and what exactly causing issue?

Regards. 

[Leo Laohoo]

Let's do the basics first ... 

Do the following: 

1.  Command:  test cable tdr interface Gi2/0/45;

2.  Wait for approximately 5 seconds; 

3.  Command:  sh cable tdr interface Gi2/0/45; and

4.  Post the output to #3.

[paul driver]

Hello

It looks like that device was seen a power device by the switch, possibly via negotiation of L2 discovery packets(CDP, LLDP) and as such tried to provide power to the port or it could be that the device wasn't at that time receiving enough power for it external source and the switch noticed this again thorough L2 discovery packets and tried to supply power, So disabling POE on the access port negated such action.

[bbiandov]

Has anyone seen the following issue with the new 30W injectors:

power-inline never does turn off POE on the switchport but those new injectors STILL somehow think there's power coming out of the switch port even when "power-inline never"

As a result the injectors do NOT supply the 30W power - that's an internal feature of the injector. If it "thinks" the switch provides power the injector simply passes through and it does not in itself supply power.

The only way to get the injector to "see" that no POE is provided is to unplug the cord from the switch port momentarily.

interface shut/no shut does not help. This is probably some hardware defect but I was wondering if a solution exists?

[bbiandov]

So I am going to post this since we got to the bottom of it and yes it is bizarre but then what isn't :)

There's some kind of defect on the switch controller so it leaks voltage even with POE specifically off. The fix is to do "(config)#default interface gigabitEthernet XX" and then paste the original config. After that no more leakage and the injector works just as expected. I was worried that a reload will put this back to the old bizarre behavior but it doesn't. Whatever the default command does it somehow affects the POE controller in a way that it start behaving the way it is supposed to. When POE is off it is really off.

Very strange?

~B