I will be changing our our LAN switches to 3560's with POE. We currently run all our IP phones with power adapters. If I plug an IP phone that has a power adapter into a POE port will it damage the switch or phone or will the switch see that it doesn't need power? I will be going around and disconnecting power on the phones before I plug them into the 3560 but I will most likely miss a couple and I don't want to damage my switch.
The inline power will only be used if it is required. CDP is used by the switch to determine what phone is connected to the port. The switch, through CDP then knows what the power requirement of the phone is. Here is an excerpt of a document:
"For Standards based compliant PDs, the Catalyst 3750/3560 Power over Ethernet controller classifies the PD at the detection stage and allocates a required power budget based on the IEEE class. If a PD supports both IEEE 802.3af and Cisco pre-standard, the PD is detected as an IEEE device. The Catalyst 3750/3560 PoE switches classify the PD at the detection stage and allocate a required power budget based on the IEEE class. Then, a CDP message determines the actual power usage for the PD, provided that CDP is enabled on the switch. If the requested power through CDP is higher than the PoE controller classified power, the requested power is adjusted to the PoE controller IEEE class."
The document is located at:
The switch, using CDP will see that the phone does not need power. The phone may, for the time it takes for CDP to update, turn off in the transition; but once CDP has updated, the power requirements will work themselves out automatically.
I just tried it here and you'll be fine. See the attachment:
Hope that answers your question!