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How to configure and verify the Transmitted Power level on APs?

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Introduction

How to configure and verify the Transmitted Power level on APs?

On Autonomous APs

Configuring Transmit Power

Use the 'power local' configuration interface command to configure the access point or bridge radio power level.

On the 2.4-GHz, 802.11g radio, you can set Orthogonal Frequency Division Multiplexing (OFDM) power levels and Complementary Code Keying (CCK) power levels. CCK modulation is supported by 802.11b and 802.11g devices. OFDM modulation is supported by 802.11g and 802.11a devices.

2.4-GHz Access Point Radio (802.11b)

power local {1 | 5 | 20 | 30 | 50 | 100 | maximum}

2.4-GHz Access Point Radio (802.11g)

power local cck {1 | 5 | 10 | 20 | 30 | 50 | 100 | maximum}
power local cck {-1 | 2 | 5 | 8 | 11 | 14 | 15 | 17 | 20 | maximum}
power local ofdm {1 | 5 | 10 | 20 | 30 | maximum}
power local ofdm {-1 | 2 | 5 | 8 | 11 | 14 | 17 | maximum}

5-GHz Access Point Radio (801.11a)

power local {5 | 10 | 20 | 40 | maximum}
power local { -1 | 2 | 5 | 8 | 11 | 14 | 15 | maximum}
power local { -1 | 2 | 5 | 8 | 11 | 14 | 15 | 17 | maximum}

1400 Series Bridge 5.8-GHz Radio

power local {12 | 15 | 18 | 21 | 22 | 23 | 24 | maximum}
This example shows how to specify a 20-mW transmit power level for the 802.11b access point radio:

AP(config-if)# power local 20

Verifying Transmit Power

Use the 'show controller dot11Radio' command. Here is an example.

This example shows how to display the radio controller status for radio interface 0:

AP# show controllers dot11radio 0

A portion of the output of this command shows the active power levels by rate, as shown below:

1.0 to 11.0  , 20  dBm, changed due to regulatory maximum
6.0 to m15.  , 17  dBm, changed due to regulatory maximum
m0.-4 to m15.-4, 14  dBm, changed due to regulatory maximum

-4 means 40-MHz wide band. A similar output, -4s means 40-MHz wide band with short guard interval turned on.

Cisco Unified Wireless Network - Configuring Transmit Power

To configure the transmit power level for all access points or a single access point in an 802.11 network, use the 'config 802.11 txPower' command.

config 802.11{a | b} txPower {global [auto | once | power_level]}
config 802.11{a | b} txPower {ap ap_name [global | power_level]} 

This example shows how to manually set the 802.11b radio transmit power to level 5 for all lightweight access points:

> config 802.11b txPower global 5

 

Verifying Transmit Power

To display the 802.11a or 802.11b automatic transmit power assignment, use the 'show advanced 802.11 txpower' command.

show advanced 802.11{a | b} txpower 

This example shows how to display the configuration and statistics of the 802.11b transmit power cost:

> show advanced 802.11b txpower

Automatic Transmit Power Assignment

  Transmit Power Assignment Mode.................. AUTO
  Transmit Power Update Interval.................. 600 seconds
  Transmit Power Threshold........................ -65 dBm
  Transmit Power Neighbor Count................... 3 APs
  Transmit Power Update Contribution.............. SN.
  Transmit Power Assignment Leader................ xx:xx:xx:xx:xx:xx
  Last Run........................................ 384 seconds ago

 

 

 

Configuring Radio Transmit Power

Beginning in privileged EXEC mode, follow these steps to set the transmit power on access point radios:

 

Command

 

Purpose

Step 1

configure terminal

Enter global configuration mode.

Step 2

interface dot11radio { 0 | 1 }

Enter interface configuration mode for the radio interface. The 2.4-GHz radio is radio 0, and the 5-GHz radio is radio 1.

Step 3

power localThese options are available for the 802.11b, 2.4-GHz radio:{ 1 | 5 | 20 | 30 | 50 | 100 | maximum }These options are available for the 5-GHz radio:{ 5 | 10 | 20 | 40 | maximum }

Set the transmit power for the 802.11b, 2.4-GHz radio or the 5-GHz radio to one of the power levels allowed in your regulatory domain. All settings are in mW.

Note The settings allowed in your regulatory domain might differ from the settings listed here.

Step 4

power localThese options are available for the 802.11g, 2.4-GHz radio:power local cck settings:{ 1 | 5 | 10 | 20 | 30 | 50 | 100 | maximum }power local ofdm settings:{ 1 | 5 | 10 | 20 | 30 | maximum }

Set the transmit power for the 802.11g, 2.4-GHz radio to one of the power levels allowed in your regulatory domain. All settings are in mW.On the 2.4-GHz, 802.11g radio, you can set Orthogonal Frequency Division Multiplexing (OFDM) power levels and Complementary Code Keying (CCK) power levels. CCK modulation is supported by 802.11b and 802.11g devices. OFDM modulation is supported by 802.11g and 802.11a devices.

Note The settings allowed in your regulatory domain might differ from the settings listed here.

Note The 802.11g radio transmits at up to 100 mW for the 1, 2, 5.5, and 11Mbps data rates. However, for the 6, 9, 12, 18, 24, 36, 48, and 54Mbps data rates, the maximum transmit power for the 802.11g radio is 30 mW.

Step 5

end

Return to privileged EXEC mode

Step 6

copy running-config startup-config

(Optional) Save your entries in the configuration file.

 

Use the no form of the power command to return the power setting to maximum, the default setting.

AIR-RM21A/AIR-RM22A Radio Modules Usually Set to Max Transmit Power

AIR-RM21A and AIR-RM22A radio modules measure transmit power in decibels per milliwatt (dBm), but earlier versions of 802.11a radios in Cisco Aironet access points measure power in milliwatts (mW). Because power settings in mW do not translate directly to settings in dBm, the access point usually uses the default power setting of maximum when you install a new AIR-RM21A or AIR-RM22A radio module.

Table lists 802.11a transmit power settings in mW and the power settings that the access point assigns to a new radio module.

Table Transmit Power Settings Assigned to New Radio Modules

Power Settings in mW

Power Setting Assigned to New Radio Module

5

5 dBm (approximately 3 mW)

10

maximum (17 dBm)

20

maximum

40

maximum

 

Limiting the Power Level for Associated Client Devices

You can also limit the power level on client devices that associate to the access point. When a client device associates to the access point, the access point sends the maximum power level setting to the client.

Beginning in privileged EXEC mode, follow these steps to specify a maximum allowed power setting on all client devices that associate to the access point:

 

 

Command

Purpose

Step 1

configure terminal

Enter global configuration mode.

Step 2

interface dot11radio { 0 | 1 }

Enter interface configuration mode for the radio interface. The 2.4-GHz radio is radio 0, and the 5-GHz radio is radio 1.

Step 3

power clientThese options are available for 802.11b, 2.4-GHz clients:{ 1 | 5 | 20 | 30 | 50 | 100 | maximum}These options are available for 802.11g, 2.4-GHz clients:{ 1 | 5 | 10 | 20 | 30 | 50 | 100 | maximum}These options are available for 5-GHz clients:{ 5 | 10 | 20 | 40 | maximum }

Set the maximum power level allowed on client devices that associate to the access point. All settings are in mW.

Note The settings allowed in your regulatory domain might differ from the settings listed here.

Step 4

end

Return to privileged EXEC mode.

Step 5

copy running-config startup-config

(Optional) Save your entries in the configuration file.

 

Use the no form of the client power command to disable the maximum power level for associated clients.

Note Aironet extensions must be enabled to limit the power level on associated client devices. Aironet extensions are enabled by default.

Reference

Comments
Beginner

Thanks for the info...  If you happen to know, I'm trying to sort out dBm versus mW for the power local command.   I'd encourage you to check out http://www.cisco.com/c/en/us/td/docs/wireless/access_point/15-3-3/configuration/guide/cg15-3-3/cg15-3-3-chap6-radio.html , which indicates settings only in dBm.  In some of your cases here, mW is indicated explicitly, and some are quite obviously dBm (such as -1).  Does this imply that for some of their gear, the "power local" command requires dBm and for other gear it's mW?  That's absurd...

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