PoE

Ø Cisco inline Power:-Power of Ethernet (POE) on Cisco Devices. Cisco introduce this back in year 2000 and cisco inline power maximum output 7.7 Watts of power. That’s was fine for many iPhone back on those days

Ø  IEEE 802.3af:- Around 2003 IEEE came out with standard. It was the IEEE 802.3af standard. It was provided exactly double what cisco inline provided. It provided 15.4 Watts of Power

Ø  IEEE 802.3at (PoE+):- More reasoned standard notified in 2009 is IEEE 802.at (PoE+). It can provide 25.5 Watts of Power. That we for use just 4 of 8 wire in that Ethernet cable but there is a way to use all 8 wire and we can double the power. We can get 51 Watts of power use of 802.at (PoE+).

Ø  Cisco universal PoE (60w) :- But not yet standard

Aside from the Power differences something else that distinguish cisco inline power from the IEEE standard is how switchport an example

                                               Will detect that it is attached to a device that want to receive power. The way cisco inline power works, is sends the tone out of port to the attached device, and if that attached device support cisco inline power, and its unpowered state currently. There is a circuit that closed, and that tone get sent to that attached device flows back to the switch. The switch send the out of tone, it our tone coming back, it conclude that this device need to receive power, and that attached device can use CDP to tell the switch how much power he needs. 

                                                  However IEEE standard instead of sending out of tone, it measure the resistance of attached device. It’s looking for a resistance around 25 Kilo Ohms. Then switch knows how much voltage it applied to wires, it sees how much current flowing, and it able to determine the resistance, and different ranges of resistance can determine, what class of device this is, different class of devices can get different amount of power. The valid range of classes is 0-4, and class 0 device means that don’t support power discovery and class 2, 3 and 4 they support different maximum power levels. However class 4 device only compatible with (PoE+)

Configuration and Verification

I have Cisco catalyst 3750 Series switch that support POE

By default POE is enabled

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