Cisco 3750 not supplying PoE initially?

[Rob Bush]

I have an odd problem here. We have some Cisco 3750 switches that are not supplying PoE power to Shoretel phones when they are plugged in. For some reason, we have to go in to the switch and do a "power inline never" and then a "power inline auto" on the port once the phone has been plugged in.

It doesn't make sense as we have confirmed that every port is set to have the power inline mode set to auto ahead of time. For some odd reason, it just doesn't power up the phone unless the phone is plugged in and THEN we issue the command.

It only seems to be happening on this one model of the switch, the 3750. We also have 3650 switches and we don't have any trouble with those at all. We're currently running 12.2(25r) of the firmware.

Any ideas?

[Rob Bush]

The plot thickens. It appears it is only 115 phones that do not power up without the power inline command issued. 230 phones *seem* to be coming up just fine. We're going to be trying a firmware upgrade soon, hopefully that resolves it!

[svalles]

Keep us posted

[Rob Bush]

Update on our issue here...

Thinking that it was possibly a firmware issue, we began the process to do an upgrade. Before the upgrade, we had a need to reboot one of the switches for a different reason without any further changes to it at all. All of the sudden, every phone is coming up correctly. That's odd... So, we reboot another 3750, and sure enough the phones work correctly and power up as expected.

We ended up upgrading the firmware anyway, but we just find it odd that a reboot of the switches magically fixed the issue. I have NO idea why this fixed anything.

[mattwray]

I have seen this if the switchport previously had a data device on it, the switch would shut off the PoE. Quick fix is just a shut/no shut of the switchport.

[nintendo1889]

For the purposes of posterity, this issue has been answered here:

https://supportforums.cisco.com/thread/2137977

The fix was applying a 2x-port mode since the phones are sending a power spike that is not 802.3af ieee compliant. It's getting close to the spec limit and the switch is protecting it's components.