PoE Switches

[shahreezal.ahmad]

Cisco PoE Switches Enquiries

1. How does PoE switches recognize which devices connected requires power?  i.e. When you plug a Cisco IP Phone, the PoE switch will power the Cisco IP Phone but when you plug in a computer, it does not power it.  What is the mechanicm behind that?
2. How does PoE switches know to provide power to PoE devices if the switch CPU is saturated (100%), does it affect PoE devices (IP Phones) ?

[Leo Laohoo]

Enhanced Power over Ethernet: Easier Deployment and Improved Mobility

FAQ:  Cisco Enhanced Power over Ethernet (PoE)

[shahreezal.ahmad]

Hi Leo,

I'm still using the normal PoE switch which have 15.4W per port.

From the feature setting of Enhanced PoE, it shows an upgrade version compare to the older PoE.

Thank you.

[Leo Laohoo]

How does PoE switches know to provide power to PoE devices if the switch CPU is saturated (100%), does it affect PoE devices (IP Phones) ?

In my line of work, if I have a switch CPU reading that goes >60% I'd start investigating.  PoE or not.

From the feature setting of Enhanced PoE, it shows an upgrade version compare to the older PoE.

PoE will support up to 15.4w.  The 3560E and the 3750E support PoE+ and can go up to 20.0w.  ePoE can go higher to 30.0w.  Very good if you have PTZ cameras.