Manage Ports Using Power Priority And The Power Budget; Determining The Power Priority For A Port - Dell C9000 Series Networking Configuration Manual

• Displaying PoE Power Allocation to Power Devices
For a complete listing of all PoE commands, see the Dell Networking OS Command Line Reference Guide.
Manage Ports using Power Priority and
the Power Budget
The allocation and return of power-on ports depends on the total inline power available in the system and
the power priority calculation.

Determining the Power Priority for a Port

The Dell Networking OS uses a sophisticated port prioritization algorithm to determine which ports receive
power so that the PoE and PoE+ ports are powered up and down deterministically.
The Dell Networking OS maintains a sorted list of PoE and PoE+ ports based on these four parameters. To
define the power priority for a port, the Dell Networking OS uses the following four parameters, in order:
1 Power-inline mode: Class or Static
NOTE: Static ports have a higher weight than Class mode ports, so all static ports always stay on top
of all class ports, regardless of the other three parameters.
2 Power inline priority configuration
3 Link layer discovery protocol-media endpoint discovery (LLDP-MED) priority the power device (PD)
sends in the Extended Power-via-medium dependent interface (MDI) type, length, value (TLV) or the
priority the PD sends in the IEEE 802.3at power-via-MDI TLV
4 Port's number
Within the set of static ports, the Dell Networking OS attempts to order the ports based on the second
parameter, power inline priority, the default of which is Low. If the Dell Networking OS finds multiple ports
with the same power-inline priority, it breaks the tie using the third parameter, the LLDP-MED Priority or
power-via-mdi priority the PD advertises, which, like the power-inline priority, can be Critical, High, or
Low. If the Dell Networking OS still finds a tie, priority is based on the fourth parameter, which is the ports
position in the port extender; there cannot be a tie based on this parameter.
The Dell Networking OS dynamically sorts this list when:
• The power-inline mode or priority changes.
• The PD advertises a different LLDP-MED priority or power-via-mdi priority
• The PD is connected or disconnected
The Dell Networking OS always uses this sorted list of ports for allocation. When you add an extra PSU,
additional ports are powered based on this list. If you remove a power supply unit (PSU), this same list is used
to remove power from the lowest priority ports.
Power over Ethernet (PoE) 874