Extended power-via-MDI information

This TLV provides significantly more information than the 802.1AB Power-via-MDI TLV referenced in 802.3 capabilities. For example, this TLV enables an Endpoint to communicate a more precise required power level, thereby enabling the device to allocate less power to the Endpoint, while making more power available to other ports.

The LLDP-MED Power-via-MDI TLV advertises an Endpoint IEEE 802.3af power-related information, including the following:

• Power type - indicates whether the LLDP-MED device transmitting the LLPDU is a power sourcing device or a powered device:
  • Power sourcing device/equipment (PSE) - This is the source of the power, or the device that integrates the power onto the network. Power sourcing devices/equipment have embedded POE technology. In this case, the power sourcing device is the RUCKUS POE device.
  • Powered device (PD) - This is the Ethernet device that requires power and is situated on the other end of the cable opposite the power sourcing device.
• Power source - The power source being utilized by a PSE or PD, for example, primary power source, backup power source, or unknown.

For Endpoint devices, the power source information indicates the power capability of the Network Connectivity Device it is attached to. When the Network Connectivity device advertises that it is using its primary power source, the Endpoint should expect to have uninterrupted access to its available power. Likewise, if the Network Connectivity device advertises that it is using backup power, the Endpoint should not expect continuous power. The Endpoint may additionally choose to power down non-essential subsystems or to conserve power as long as the PSE is advertising that it is operating on backup power.

• Power priority - The in-line power priority level for the PSE or PD:
  • 3 - low
  • 2 - high
  • 1 - critical
  • unknown
• Power level - The total power, in tenths of watts, required by a PD from a PSE, or the total power a PSE is capable of sourcing over a maximum length cable based on its current configuration.

If the exact power is not known for a PSE or PD, it will advertise the power level associated with its 802.3af power class listed in the following table.

For a PD (Endpoint device), the power level represents the maximum power it can consume during normal operations in its current configuration, even if its actual power draw at that instance is less than the advertised power draw.

For a PSE (Network Connectivity device), the power level represents the amount of power that is available on the port at the time. If the PSE is operating in reduced power (i.e., it is using backup power), the reduced power capacity is advertised as long as the condition persists.

By default, LLDP-MED power-via-MDI information is automatically advertised when LLDP-MED is enabled, the port is a POE port, and POE is enabled on the port. To disable this advertisement, enter a command such as the following.

device(config)# no lldp advertise med-power-via-mdi ports e 1/2/4 to 1/2/12

The LLDP-MED power-via-MDI advertisement will appear similar to the following on the remote device, and in the CLI display output on the RUCKUS device (show lldp local-info ).

+ MED Extended Power via MDI
    Power Type     : PSE device
    Power Source   : Unknown Power Source
    Power Priority : Low (3)
    Power Value    : 6.5 watts (PSE equivalent: 7005 mWatts)