Administrator Guide

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.
• Type — Displayed in the show power inline EXEC command and is used only when the PD is Type1 or Type2. The Type1 or Type2 PSE
requests are not used.
• Priority — Used for priority calculation.
• PD requested power value — Used for power allocation.
• PSE allocated power value — Used to check whether the PD is in sync with the PSE.
NOTE:
For more information about the advertise med power-via-mdi and advertise dot3-tlv power-via-mdi
commands, refer to the Dell Command Line Reference Guide .
Power over Ethernet (PoE) 583