x600 Series Layer 3 Gigabit Ethernet Switches Installation Guide
Power Over Ethernet (PoE and PoE+)
The following section applies to
Gigabit Ethernet switches only.
The
Power over Ethernet (PoE), defined in the IEEE 802.3af standard.
The
Power over Ethernet Plus (PoE+), defined in the IEEE 802.3at standard.
PoE is a mechanism for supplying power to network devices over the same twisted pair cables used to carry network traffic. This feature can simplify network installation and maintenance by allowing you to use the switch as a central power source for other network devices.
A device that receives its power over an Ethernet cable is called a Powered Device (PD). Examples of such devices are wireless access points, IP telephones, web cams, and even other Ethernet switches. A powered device connected to a port on the switch will receive both network traffic and power over the same twisted pair cable.
There are several advantages that PoE add to the installation and maintenance of your network. First, because the switch acts as the central power source for your powered devices, adding an uninterruptible power source (UPS) to the switch increases the protection not just to the switch itself from possible power source problems, but also to all of the powered devices connected to it. This can increase the reliability of your network by minimizing the impact to network operations from a power failure.
PoE can also simplify the installation of your network. A frequent issue in selecting a location for a network device is whether there is a power source nearby. This often limits equipment placement or requires the added cost and time of having additional electrical sources installed. With PoE, you can install
The switch automatically determines whether or not a device connected to a port is a PD. A PD has a signature resistor or capacitor that the switch can detect over the Ethernet cabling. If the resistor or capacitor is present, the switch assumes that the device is a PD.
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