Friday, 4 July 2014

Cisco Access Points: Which Power Levels Does My AP Support?

Cisco APs support a number of discrete transmit power levels which are 3dB apart. They are usually numbered levels 1 (highest) down to 7 or 6 (lowest).

The numbers of levels and the transmit power values assigned vary between models and regions.

The quickest way to determine the levels supported by your AP is to logon to your WLC and execute the following CLI command:

show ap config 802.11b <ap-name>

This will list out a whole lot of information, including a section which starts with the title: "TX Power". This contains the levels and corresponding dBm levels supported. Here is a sample:

Tx Power
      Num Of Supported Power Levels ............. 6
      Tx Power Level 1 .......................... 16 dBm
      Tx Power Level 2 .......................... 13 dBm
      Tx Power Level 3 .......................... 10 dBm
      Tx Power Level 4 .......................... 7 dBm
      Tx Power Level 5 .......................... 4 dBm
      Tx Power Level 6 .......................... 1 dBm
      Tx Power Configuration .................... AUTOMATIC
      Current Tx Power Level .................... 6
      Tx Power Assigned By ...................... DTPC

A quicker way to get the same information (that doesn't involve lots of scrolling through text) is to use the grep command (introduced in 7.5):

grep include "Tx Power Level" "show ap config 802.11b <ap-name>"

This gives the output:

      Tx Power Level 1 .......................... 16 dBm
      Tx Power Level 2 .......................... 13 dBm
      Tx Power Level 3 .......................... 10 dBm
      Tx Power Level 4 .......................... 7 dBm
      Tx Power Level 5 .......................... 4 dBm
      Tx Power Level 6 .......................... 1 dBm
      Current Tx Power Level .................... 6

The example above shows the levels for the 2.4GHz radio. To provide the same information for the 5GHz radio, use the command:

show ap config 802.11a <ap-name>

Addendum from Jake Snyder (@jsnyder81)

Jake sent me a great piece of advise via Twitter: "if tx power levels are what you want, "show advanced 802.11x txpower" is very quick.  Multiple APs, multiple bands."

Sure enough, the following commands give a nice condensed output for every AP:

  • show advanced 802.11b txpower
  • show advanced 802.11a txpower

Here is some sample output:


(wlc) >show advanced 802.11b txpower

Leader Automatic Transmit Power Assignment
  Transmit Power Assignment Mode................. AUTO
  Transmit Power Update Interval................. 600 seconds
  Transmit Power Threshold....................... -70 dBm
  Transmit Power Neighbor Count.................. 3 APs
  Min Transmit Power............................. -10 dBm
  Max Transmit Power............................. 30 dBm
  Update Contribution
    Noise........................................ Enable
    Interference................................. Enable
    Load......................................... Disable
    Device Aware................................. Disable
  Transmit Power Assignment Leader............... wlc (10.1.1.99)
  Last Run....................................... 345 seconds ago
  Last Run Time.................................. 0 seconds
  TPC Mode....................................... Version 1
  TPCv2 Target RSSI.............................. -67 dBm
  TPCv2 VoWLAN Guide RSSI........................ -67.0 dBm
  TPCv2 SOP...................................... -85.0 dBm
  TPCv2 Default Client Ant Gain..................   0.0 dBi
  TPCv2 Path Loss Decay Factor...................   3.6
  TPCv2 Search Intensity......................... 10 Iterations


AP Name                          Channel    TxPower       Allowed Power Levels
-------------------------------- ---------- ------------- ------------------------
ap1                              *13         2/6 (13 dBm) [16/13/10/7/4/1/1/1]
ap2                              *9          3/6 (10 dBm) [16/13/10/7/4/1/1/1]
ap3                              *1          3/6 (10 dBm) [16/13/10/7/4/1/1/1]
ap4                              *9          3/6 (10 dBm) [16/13/10/7/4/1/1/1]
ap5                              *1         *3/6 (10 dBm) [16/13/10/7/4/1/1/1]
ap6                              *5         *3/6 (10 dBm) [16/13/10/7/4/1/1/1]
ap7                              *13         3/6 (10 dBm) [16/13/10/7/4/1/1/1]
ap8                              *5         *6/6 ( 1 dBm) [16/13/10/7/4/1/1/1]
ap9                              *1          3/6 (10 dBm) [16/13/10/7/4/1/1/1]
ap10                             *13        *6/6 ( 1 dBm) [16/13/10/7/4/1/1/1]
ap11                             *5         *6/6 ( 1 dBm) [16/13/10/7/4/1/1/1]
ap12                             *5          3/6 (10 dBm) [16/13/10/7/4/1/1/1]
ap13                             *1         *6/6 ( 1 dBm) [16/13/10/7/4/1/1/1]
ap14                             *1         *6/6 ( 1 dBm) [16/13/10/7/4/1/1/1]
ap15                             *5         *4/6 ( 7 dBm) [16/13/10/7/4/1/1/1]


Notes

For my own persoanl reference, here are the outputs from a couple of APs in my lab. These are taken from a 2602i and 2602i. Note that these are 'E' domain APs, so may not applt to your region:

grep include "Tx Power Level" "show ap config 802.11b AP2600"

      Tx Power Level 1 .......................... 16 dBm
      Tx Power Level 2 .......................... 13 dBm
      Tx Power Level 3 .......................... 10 dBm
      Tx Power Level 4 .......................... 7 dBm
      Tx Power Level 5 .......................... 4 dBm
      Current Tx Power Level .................... 1

grep include "Tx Power Level" "show ap config 802.11a AP2600"

      Tx Power Level 1 .......................... 18 dBm
      Tx Power Level 2 .......................... 15 dBm
      Tx Power Level 3 .......................... 12 dBm
      Tx Power Level 4 .......................... 9 dBm
      Tx Power Level 5 .......................... 6 dBm
      Current Tx Power Level .................... 1

grep include "Tx Power Level" "show ap config 802.11b AP3600"

      Tx Power Level 1 .......................... 18 dBm
      Tx Power Level 2 .......................... 15 dBm
      Tx Power Level 3 .......................... 12 dBm
      Tx Power Level 4 .......................... 9 dBm
      Tx Power Level 5 .......................... 6 dBm
      Tx Power Level 6 .......................... 3 dBm

grep include "Tx Power Level" "show ap config 802.11a AP3600"

      Tx Power Level 1 .......................... 18 dBm
      Tx Power Level 2 .......................... 15 dBm
      Tx Power Level 3 .......................... 12 dBm
      Tx Power Level 4 .......................... 9 dBm
      Tx Power Level 5 .......................... 6 dBm

      Tx Power Level 6 .......................... 3 dBm