Allied Telesis X3112 User Manual

Page of 104
SwitchBlade x3112 Installation Guide
33
AT-SBx31GP24
Power over 
Ethernet
The twisted-pair ports on the AT-SBx31GP24 PoE Line Card feature 
Power over Ethernet (PoE). 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 PD 
connected to a port on the switch receives both network traffic and power 
over the same twisted-pair cable.
The AT-SBx31GP24 automatically determines whether a device 
connected to a port is a PD or not. A PD has a signature resistor or 
signature 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.
A port connected to a network node that is not a PD (that is, a device that 
receives its power from another power source) functions as a regular 
Ethernet port, without PoE. The PoE feature remains enabled on the port 
but no power is delivered to the device.
Power Budgeting 
The AT-SBx31GP24 PoE Line Card is capable of providing a maximum of 
30W of power per port on all 24 ports for a total power consumption of 720 
W, while at the same time furnishing standard 10/100/1000 Mbps Ethernet 
functionality. See Table 8 on page 34 for the matrix of Class versus power 
level output and the maximum number of ports.
Note
The maximum number of PoE ports in the SwitchBlade x3112 
Switch is 240 ports.