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Chapter 2: Overview of the Ethernet Line Cards
Power Budgeting
PoE Wiring
58
The power source for the PoE feature on the ports of the AT-SBx31GP24
Line Cards is the AT-SBxPWRPOE1 AC PoE Power Supply. The chassis
can have two PoE power supplies. The AT-SBxPWRPOE1 AC PoE Power
Supply has a power budget of 1200 watts for powered devices.
Consequently, the chassis has a power budget of 1200 watts with one
power supply and 2400 watts with two power supplies.
The number of powered devices the chassis can support at one time
depends on the number of AT-SBxPWRPOE1 AC PoE Power Supplies in
the chassis and the power requirements of the powered devices in your
network. Table 16 lists the maximum number of powered devices by class,
for one or two power supplies. The numbers assume that the powered
devices require the maximum amount of power for their classes.
Note
The maximum number of PoE ports in the SwitchBlade x3106
Switch is 240 ports.
Table 16. Maximum Number of Powered Devices
Class
0
1
2
3
4
The IEEE 802.3af and 802.3at standards define two methods for
delivering power to powered devices over the four pairs of strands that
comprise a standard Ethernet twisted-pair cable. The methods are called
Alternatives A and B. In Alternative A, power is supplied to powered
devices on strands 1, 2, 3, and 6, which are the same strands that carry
the 10/100Base-TX network traffic. In Alternative B, power is delivered on
strands 4, 5, 7, and 8. These are the unused strands.
Note
1000BASE-T cables carry the network traffic on all eight strands of
the Ethernet cable.
Maximum Number of
Ports with
One PoE PSU
(1200 W)
77
120
120
77
40
Maximum Number of
Ports with
Two PoE PSU's
(2400 W)
120
120
120
120
80
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