C I S C O C O N F I D E N T I A L - D r a f t A 1
3-7
Cisco Aironet 1250 Series Access Point Hardware Installation Guide
OL-8247-02
Chapter 3 Troubleshooting 1250 Series Autonomous Access Points
Low Power Condition on Autonomous Access Points
Low Power Condition on Autonomous Access Points
The access point 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) requires 12.95 W (up to 15 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 18.4 W (up to 21 W with
100 m CAT 5E
(or higher) Ethernet cable.
Caution
Current switches, power patch pannels, and IEEE 802.3af compliant power sources are not able to
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
“Checking the Autonomous Access Point
and
“Inline Power Status Messages” section on page 3-8
Intelligent Power Management - need changes
The access point requires
18.4 W of power for dual radio operation or 12.95 W of power with a single
radio module installed
( needs
----TBD 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.
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.
