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New Member

PoE/Inline Power and external power at the same time


if I have two power sources (external power and PoE/Inline Power) at the same time: which power source does the IP phone use? What happens if I attach the external power supply after the phone has received power from the switch?

Any hint is welcome.

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New Member

Re: PoE/Inline Power and external power at the same time

Hope this will help your!

Power Source Design:

The phone and switch automatically determine which power source the phone

uses. If the power has to be switched to a different source, the phone user will

experience different results based on which power source is being used by the


? If you plug a phone into the optional power supply before plugging it into the

network, the phone is powered by the power supply.

? If you then unplug the phone from the power supply, the phone resets. If the

switch port is configured for 10/100 Mbps, the switch recognizes the loss of

power and brings the phone back up.

? If the switch port is configured for 10 Mbps only, then you must unplug the

network connection and replug it into the phone for the switch to recognize

the phone?s loss of power.

? If, however, you plugged the network connection into the phone before you

plugged in the power cord, the phone receives power through the switch, and

unplugging the power cord will not bring down the phone. If the switch

reboots, the phone will then be powered by the power cord.

Redundancy Feature:

For redundancy, you can use the Cisco AC adapter even if you are using inline

power from the Cisco Catalyst switches. The Cisco IP Phone can share the power

load being used from the inline power and external power source. If either the

inline power or the external power goes down, the phone can switch entirely to the

other power source.

To use this redundancy feature:

1. Set the inline power mode to auto on the Cisco Catalyst switch.

2. Connect the unpowered Cisco IP Phone to the network.

3. Connect the external power supply to the phone after the phone powers up.