Low Power Condition For Lightweight Access Points; Intelligent Power Management - Cisco AIR-AP1252AG-A-K9 Hardware Installation Manual

Chapter 4 Troubleshooting 1250 Series Lightweight Access Points

Low Power Condition for Lightweight Access Points

The access point with two radio modules can be powered from the 1250 DC power module or from the
1250 in-line power injector. The access point supports the Cisco Intelligent Power Management.
With only one radio module installed, the access point (powered device) can be powered by an 802.3af
power source. The access point requires 15.4 W with 100 m of CAT 5E (or higher) 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 power injector, is higher by an amount dependent on the length of the
interconnecting cable.
For full dual radio module operation, the access point requires 18.5 W with 100 m CAT 5E (or higher)
Ethernet cable.
Current switches, power patch pannels, and IEEE 802.3af compliant power sources are not able to
Caution
provide sufficient power to the access point with both radio modules installed.
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, displays a low power message on the browser
and serial interfaces, and creates an event log entry (see the
LEDs" section on page 4-3

Intelligent Power Management

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.
Note Independent of the power negotiations, the access point hardware also uses the 802.3af classification
scheme to indicate the power required from the power source. However, the power source cannot report
the power available to the access point unless the power source also supports Intelligent Power
Management.
Some Cisco switches that are capable of supplying sufficient power require a software upgrade to
support Intelligent Power Management. If the software upgrade is not desired, you can configure the
access point to operate in pre-standard compatibility mode and the access point automatically enters full
power mode if these Cisco switches are detected in the received CDP ID field.
OL-8247-03
and the "Inline Power Status Messages" section on page
Cisco Aironet 1250 Series Access Point Hardware Installation Guide
Low Power Condition for Lightweight Access Points
"Checking the Lightweight Access Point
4-8).
4-7