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IEEE 802.3af (PoE) and IEEE 802.3at (PoE+) Support on Cisco Meraki MS Switches

The IEEE 802.3af (PoE) standard supports the delivery of power over Ethernet up to 15.4W per port that may be used to deliver power to a variety of devices. However, only 12.95W is assured to be available at the powered device as some power is dissipated in the cable as overhead.

The IEEE 802.3at (PoE+) standard supports up to 25.5W of power on the ports, allowing devices that require more than 15.4W to power on when connected to the PoE+ ports.

MS-Supported Protocols

The MS series supports current-based PoE classification. Layer-2 (LLDP/CDP) is also supported on switches with newer firmware.

To ensure that you are using the latest stable firmware version, please refer to our Firmware FAQ for instructions.

Current Classification

Based on the classification current used by the device, the MS switch will classify the device as a Class 0,1,2,3 or 4 type device and apply the proper standards-defined behaviors to the port.

 

Table 1 - Power levels available
Class Usage Classification current
[mA]
Power range
[Watt]
Class description
0 Default 0–4 0.44–12.94 Classification unimplemented
1 Optional 9–12 0.44–3.84 Very Low power
2 Optional 17–20 3.84–6.49 Low power
3 Optional 26–30 6.49–12.95 Mid power
4 Valid for 802.3at (Type 2) devices,
not allowed for 802.3af devices
36–44 12.95–25.50 High power

Monitoring PoE on Dashboard

When PoE devices are connected to the ports of the MS PoE switches, the ports on the switches are labeled with a "P" or lightening bolt. This symbol indicates that power from these interfaces is being supplied be the switch (PSE) to the powered device(s) (PD). See an example below:

 

PoE consumption on the switch can be monitored live, including both a consumption and budgeting value as well as port-specific information. For more information on available PoE budget, please see the MS Family Datasheet.

 

Note: The switches will budget based on the PoE device classification, the budget is allowed to exceed available power as it's used to gauge overall power that might be consumed on the switch. Devices will continue to be powered until the consumption goes over the available amount of power. In this case the lowest port numbers take precedence and power will be pulled from the highest ports thus denying them power.

PoE Underload Alerts

A PoE underload event occurs when a PoE power consuming device uses less power than the specification allows for a long enough period of time. This can happen if a PoE device is not operating correctly or if a device powers down too slowly.

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Last modified
12:54, 12 Jul 2017

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ID: 1134

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