Power Over Ethernet Ports - Cisco Catalyst 2960-XR Configuration Manual

Configuring PoE
Table 12: IEEE Power Classifications
Class
0 (class status unknown)
1
2
3
4
The switch monitors and tracks requests for power and grants power only when it is available. The switch
tracks its power budget (the amount of power available on the switch for PoE). The switch performs
power-accounting calculations when a port is granted or denied power to keep the power budget up to date.
After power is applied to the port, the switch uses CDP to determine the CDP-specific power consumption
requirement of the connected Cisco powered devices, which is the amount of power to allocate based on the
CDP messages. The switch adjusts the power budget accordingly. This does not apply to third-party PoE
devices. The switch processes a request and either grants or denies power. If the request is granted, the switch
updates the power budget. If the request is denied, the switch ensures that power to the port is turned off,
generates a syslog message, and updates the LEDs. Powered devices can also negotiate with the switch for
more power.
With PoE+, powered devices use IEEE 802.3at and LLDP power with media dependent interface (MDI) type,
length, and value descriptions (TLVs), Power-via-MDA TLVs, for negotiating power up to 30 W. Cisco
pre-standard devices and Cisco IEEE powered devices can use CDP or the IEEE 802.3at power-via-MDI
power negotiation mechanism to request power levels up to 30 W.
The initial allocation for Class 0, Class 3, and Class 4 powered devices is 15.4 W. When a device starts
Note
up and uses CDP or LLDP to send a request for more than 15.4 W, it can be allocated up to the maximum
of 30 W.
The CDP-specific power consumption requirement is referred to as the actual power consumption
Note
requirement in the software configuration guides and command references.
If the switch detects a fault caused by an undervoltage, overvoltage, overtemperature, oscillator-fault, or
short-circuit condition, it turns off power to the port, generates a syslog message, and updates the power
budget and LEDs.
The PoE feature operates the same whether or not the switch is a stack member. The power budget is per-switch
and independent of any other switch in the stack. Election of a new active switch does not affect PoE operation.
The active switch keeps track of the PoE status for all switches and ports in the stack and includes the status
in output displays.
OL-29420-01
Catalyst 2960-XR Switch Interface and Hardware Component Configuration Guide, Cisco IOS Release 15.0(2)EX1

Power over Ethernet Ports

Maximum Power Level Required from the Switch
15.4 W
4 W
7 W
15.4 W
30 W (For IEEE 802.3at Type 2 powered devices)
85