Assigning PoE priority with two or more modules

Ports across two or more modules can be assigned a class priority of low (the default), high, or critical. For example, A5, B7, and C10 could all be assigned a priority class of Critical. When power is allocated to the ports on a priority basis, the Critical priority power requests are allocated to module A first, then Module B, then C, and so on. Next, the High priority power requests are allocated, starting with module A, then B, then C, and the remaining modules in order. Any remaining power is allocated in the same manner for the Low priority ports, beginning with module A though the remaining modules. If there is not enough PoE power for all the PDs connected to PoE modules in the switch, power is allocated according to priority class across modules.

All ports on module C are prioritized as Critical.

switch# interface c1-c24 power-over-ethernet

All ports on module A are prioritized as Low.

switch# interface a1-a24 power-over-ethernet

There are 48 PDs attached to all ports of modules A and C (24 ports each module); however, there is enough PoE power for only 32 ports (8.5 watts × 32 ports=273 watts.) The result is that all the Critical priority ports on module C receive power, but only 8 ports on module A receive power.

On module A, the port A1 has the highest priority of the ports in that module if all ports are in the same priority class, which is the case for this example. Since a minimum 17 + 5 watts of power is allocated per PoE module for PoE, port A1 will always receive PoE power. If another port on module A had a higher priority class than port A1, that port would be allocated the power before port A1.

For PoE+ modules there must be a minimum of 33 + 5 watts of power allocated per PoE+ module.