Cisco Systems 1240AG manual Low Power Condition for Lightweight Access Points

Chapter 4 Troubleshooting 1240AG Series Lightweight Access Points

Low Power Condition for Lightweight Access Points

Low Power Condition for Lightweight Access Points

Warning This product must be connected to a Power over Ethernet (PoE) IEEE 802.3af compliant power source or an IEC60950 compliant limited power source. Statement 353

The access point can be powered from the 48-VDC power module or from an in-line power source. The access point supports the IEEE 802.3af power standard, Cisco Pre-Standard PoE protocol, and Cisco Intelligent Power Management for in-line power sources.

For full operation, the access point (powered device) requires 12.95 W (up to 15.4 W with 100 m CAT 5 Ethernet cable). When the access point is being used in a PoE configuration, the power drawn from the power sourcing equipment (PSE), such as a switch or power injector, is higher by an amount dependent on the length of the interconnecting cable.

The power module and Cisco Aironet power injectors are capable of supplying the required power for full operation, but some inline power sources are not capable of supplying sufficient power. Also, some high-power inline power sources, might not be able to provide up to 15.4 W of power to all ports at the same time.

Note An 802.3af compliant switch (Cisco or non-Cisco) is capable of supplying sufficient power for full operation.

Note If your access point is connected to in-line power, do not connect the power module to the access point. Using two power sources on the access point might cause the access point to shut down to protect internal components and might cause the switch to shut down the port to which the access point is connected. If your access point shuts down, you must remove all power and reconnect only a single power source.

On power up, the access point is placed into low power mode (both radios are disabled), Cisco IOS software loads and runs, and power negotiation determines if sufficient power is available. If there is sufficient power then the radios are turned on; otherwise, the access point remains in low power mode with the radios disabled to prevent a possible over-current condition. In low power mode, the access point activates the Status LED low power error indication (see the “Checking the Lightweight Access Point LEDs” section on page 4-3).

Intelligent Power Management

The access point requires 12.95 W of power (up to 15.4 W with 100 m CAT 5 Ethernet cable) for full power operation with both radios, but only needs 6.3 W of power when operating in low power mode with both radios disabled. To help avoid an over-current condition with low power sources and to optimize power usage on Cisco switches, Cisco developed Intelligent Power Management, which uses Cisco Discovery Protocol (CDP) to allow powered devices (such as your access point) to negotiate with a Cisco switch for sufficient power.

The access point supports Intelligent Power Management and as a result of the power negotiations, the access point will either enter full power mode or remain in low power mode with the radios disabled.

Cisco Aironet 1240AG Series Access Point Hardware Installation Guide

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