Administrator Guide

(Watts) (Watts) (Watts) (%) (Watts) (Watts) (Watts) (Watts)
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1 1100 150 0 99 940 0 0 940
Dell#
Manage Ports using Power Priority and 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.
You can manage the power prioritization and the power allocation to the ports by using the power inline priority and
power budget commands. For more information about the commands, see the Dell Networking OS Command Line Reference
Guide.
Determine the Power Priority
Dell Networking OS uses a sophisticated port prioritization algorithm to determine which ports should receive power so that the
PoE and PoE+ ports are powered up and down deterministically.
Dell Networking OS uses the following four parameters for defining the power priority for a port:
1. Power inline mode: class or static.
2. Power inline priority configuration.
3. LLDP-MED priority sent by the PD in the Extended Power-via-MDI TLV or the priority sent by the PD in the IEEE 802.3at
power-via-mdi TLV.
4. Slot and port number.
Dell Networking OS maintains a sorted list of PoE/PoE+ ports based on the above parameters. The static ports have higher
weight than class mode ports. Hence all static ports always stay on top of all class ports, regardless of the other parameters.
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 can be Critical,
High, or Low. If the Dell Networking OS still finds a tie, the priority is based on the fourth parameter, which is the position of
the port number in the switch. 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 power supply unit (PSU), the
additional ports are powered based on this list. If you remove a PSU, the same list is used to remove power from the ports with
lowest priority.
Advertising Extended Power
The power device(PD) sends the information in the LLDP-MED extended power via MDI TLV and information in the IEEE 802.3
power via MDI TLV.
Dell Networking OS uses the following information sent through LLDP-MED extended power-via-MDI TLV. The power is
advertised using the advertise med power-via-mdi command.
● Power Requirement — Used for power allocation.
● Power Priority — Used for priority calculation. The values are: Critical, High, Low.
● External Power Source — Not used.
Dell Networking OS uses the following information sent through IEEE 802.3 power-via-mdi TLV. The power is advertised using
the advertise dot3-tlv power-via-mdi command.
● Power Class — Displayed in the show power inline EXEC command. The PD-requested power value must be within the
limits of the maximum watts.
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Power over Ethernet (PoE)