Cisco IOS Software Configuration Guide for Cisco Aironet 1300 Series Outdoor Access Point/Bridge 12.3(7)JA
Configuring Radio Settings
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Configuring Radio Settings

Table Of Contents

Configuring Radio Settings

Enabling the Radio Interface

Configuring the Role in Radio Network

Configuring Radio Data Rates

Configuring Radio Transmit Power

Limiting the Power Level for Associated Client Devices

Configuring Radio Channel Settings

Configuring LBS on Access Points

Enabling and Disabling World Mode

Disabling and Enabling Short Radio Preambles

Configuring Transmit and Receive Antennas

Aironet Extensions

Configuring the Ethernet Encapsulation Transformation Method

Enabling and Disabling Concatenation

Configuring the Radio Distance Setting

Enabling and Disabling Reliable Multicast to Workgroup Bridges

Enabling and Disabling Public Secure Packet Forwarding

Configuring Protected Ports

Enabling Short Slot Time

Configuring the Beacon Period and the DTIM

Configure RTS Threshold and Retries

Configuring the Maximum Data Retries

Configuring the Fragmentation Threshold

Setting the Root Parent Timeout Value

Configuring the Root Parent MAC

Performing a Carrier Busy Test


Configuring Radio Settings


This chapter describes how to configure radio settings for your access point/bridge. This chapter includes these sections:

Enabling the Radio Interface

Configuring the Role in Radio Network

Configuring Radio Data Rates

Configuring Radio Transmit Power

Configuring Radio Channel Settings

Enabling and Disabling World Mode

Disabling and Enabling Short Radio Preambles

Configuring Transmit and Receive Antennas

Aironet Extensions

Configuring the Ethernet Encapsulation Transformation Method

Enabling and Disabling Concatenation

Configuring the Radio Distance Setting

Enabling and Disabling Reliable Multicast to Workgroup Bridges

Enabling and Disabling Public Secure Packet Forwarding

Enabling Short Slot Time

Configuring the Beacon Period and the DTIM

Configure RTS Threshold and Retries

Configuring the Maximum Data Retries

Configuring the Fragmentation Threshold

Setting the Root Parent Timeout Value

Configuring the Root Parent MAC

Performing a Carrier Busy Test

Enabling the Radio Interface

The radio interface is disabled by default.


Note In Cisco IOS Release 12.3(7)JA there is no default SSID. You must create an SSID before you can enable the radio interface.


Beginning in privileged EXEC mode, follow these steps to enable the access point/bridge radio:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

ssid string

Enter the Radio Service Set Identifier. The SSID can consist of up to 32 alphanumeric characters. SSIDs are case sensitive.

Step 4 

end

Return to privileged EXEC mode.

Step 5 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

The radio is enabled when you set the SSID.

Configuring the Role in Radio Network

You can configure your access point/bridge as a root bridge, non-root bridge, access point, or workgroup bridge. Figure 6-1 shows a root bridge communicating with a non-root bridge in a point-to-point configuration.

Figure 6-1 Point-to-Point Bridge Configuration

Figure 6-2 shows a typical configuration where the bridge functions as an access point.

Figure 6-2 Access Point Configuration

Figure 6-3 shows how the bridge performs when configured as a workgroup bridge.

Figure 6-3 Workgroup Bridge Configuration

Beginning in privileged EXEC mode, follow these steps to set the access point/bridge's radio network role:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

station role

install {automatic | non-root | root}

non-root {bridge | wireless clients}

repeater

root {access-point | ap-only | [bridge | wireless-clients] | [fallback | repeater | shutdown]}

scanner

workgroup-bridge

Set the access point/bridge role.

install—Places the access point/bridge in a bridge link setup mode for antenna alignment purposes. The automatic option configures teh access point/bridge to automatically search for a link to another access point/bridge or an access point in bridge mode. The root and non-root options allow you to manually configure the access point/bridge.

non-root—Places the access point/bridge in non-root bridge mode. The wireless clients option allows clients to associate to the non-root access point/bridge while it is in the non-root bridge mode.

root—Places the access point/bridge in root bridge mode. The ap-only option makes the access point act as a root access point (the default station role).

scanner—Causes the access point/bridge to operate as as scanner only and does not accept associations from client devices. As a scanner, the access point/bridge collects radio data and sends it to the WDS server on your network.

Note The scanner mode is supported only when used with a WLSE device on your network.

workgroup-bridge—Places the access point/bridge in the workgroup bridge mode. As a workgroup bridge, the access point/bridge associates to an access point or bridge as a client and provides a wireless LAN connection for devices connected to its Ethernet port.

Step 4 

mobile station

(Optional) Use this command to configure a non-root bridge as a mobile station. When this feature is enabled the non-root bridge scans for a new parent association when it encounters a poor Received Signal Strength Indicator (RSSI), excessive radio interference, or a high frame-loss percentage. Using these criteria, the access point/bridge searches for a new root association and roams to a new root bridge before it loses its current association. When the mobile station setting is disabled (the default setting) the bridge does not search for a new association until it loses its current association.

Step 5 

end

Return to privileged EXEC mode.

Step 6 

copy running-config startup-config

(Optional) Save your entries in the configuration file.


Note See Chapter 20, "Configuring Repeater and Standby Access Points and Workgroup Bridge Mode," for more information about configuring the access point/bridge as an access point or workgroup bridge.


Configuring Radio Data Rates

You use the data rate settings to choose the data rates the access point/bridge uses for data transmission. The rates are expressed in megabits per second. The access point/bridge always attempts to transmit at the highest data rate set to Basic, also called Require on the browser-based interface. If there are obstacles or interference, the access point/bridge steps down to the highest rate that allows data transmission. You can set each data rate to one of three states:

Basic (this is the default state for all data rates)—Allows transmission at this rate for all packets, both unicast and multicast. At least one of the access point/bridge's data rates must be set to Basic.

Enabled—The access point/bridge transmits only unicast packets at this rate; multicast packets are sent at one of the data rates set to Basic.

Disabled—The access point/bridge does not transmit data at this rate.


Note At least one data rate must be set to basic.


You can use the Data Rate settings to set the access point/bridge to serve client devices operating at specific data rates. For example, to set the 2.4-GHz radio for 11 megabits per second (Mbps) service only, set the 11-Mbps rate to Basic and set the other data rates to Disabled. To set the wireless device to serve only client devices operating at 1 and 2 Mbps, set 1 and 2 to Basic and set the rest of the data rates to Disabled. To set the 2.4-GHz, 802.11g radio to serve only 802.11g client devices, set any Orthogonal Frequency Division Multiplexing (OFDM) data rate (6, 9, 12, 18, 24, 36, 48, 54) to Basic.

You can also configure the access point/bridge to set the data rates automatically to optimize either range or throughput. When you enter range for the data rate setting, the access point/bridge sets the 6-Mbps rate to basic and the other rates to enabled. When you enter throughput for the data rate setting, the access point/bridge sets all data rates to basic. Enter default to set the data rates to factory defaults

Beginning in privileged EXEC mode, follow these steps to configure the radio data rates:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

speed

{[1.0] [2.0] [5.5] [6.0] [9.0] [11.0] [12.0] [18.0] [24.0] [36.0] [48.0] [54.0] [basic-1.0] [basic-2.0] [basic-5.5] [basic-6.0] [basic-9.0] [basic-11.0] [basic-12.0] [basic-18.0] [basic-24.0] [basic-36.0] [basic-48.0] [basic-54.0] | range |
throughput [ofdm] | default }

Set each data rate to basic or enabled, or enter range to optimize range or throughput to optimize throughput.

Enter 1.0, 2.0, 5.5, 6.0, 9.0, 11.0, 12.0, 18.0, 24.0, 36.0, 48.0, and 54.0 to set these data rates to enabled on the 802.11g, 2.4-GHz radio.

Enter basic-1.0, basic-2.0, basic-5.5, basic-6.0, basic-9.0, basic-11.0, basic-12.0, basic-18.0, basic-24.0, basic-36.0, basic-48.0, and basic-54.0 to set these data rates to basic on the 802.11g, 2.4-GHz radio.

Note The client must support the basic rate that you select or it cannot associate to the wireless device. If you select 12 Mbps or higher for the basic data rate on the 802.11g radio, 802.11b client devices cannot associate to the wireless device 802.11g radio.

(Optional) Enter range or throughput or ofdm-throughput (no ERP protection) to automatically optimize radio range or throughput. When you enter range, the wireless device sets the lowest data rate to basic and the other rates to enabled. When you enter throughput, the wireless device sets all data rates to basic.

(Optional) Enter speed throughput ofdm to set all OFDM rates (6, 9, 12, 18, 24, 36, and 48) to basic (required) and set all the CCK rates (1, 2, 5.5, and 11) to disabled. This setting disables 802.11b protection mechanisms and provides maximum throughput for 802.11g clients. However, it prevents 802.11b clients from associating to the access point.

(Optional) Enter default to set the data rates to factory default settings (not supported on 802.11b radios).

On the 802.11g radio, the default option sets rates 1, 2, 5.5, and 11 to basic, and rates 6, 9, 12, 18, 24, 36, 48, and 54 to enabled. These rate settings allow both 802.11b and 802.11g client devices to associate to the wireless device 802.11g radio.

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 speed command to disable data rates. When you use the no form of the command, all data rates are disabled except the rates you name in the command. This example shows how to disable data rate 6.0:

ap# configure terminal
ap(config)# interface dot11radio 0
ap(config-if)# no speed basic-9.0 basic-12.0 basic-18.0 basic-24.0 basic-36.0 basic-48.0 
basic-54.0
ap(config-if)# end

Data rate 6 is disabled, and the rest of the rates are set to basic.

This example shows how to set up the access point/bridge for 54-Mbps service only:

ap# configure terminal
ap(config)# interface dot11radio 0
ap(config-if)# speed basic-54.0
ap(config-if)# end

Data rate 54 is set to basic, and the rest of the data rates are set to enabled.

Configuring Radio Transmit Power

Radio transmit power is based on the radio installed in your access point/ and the regulatory domain in which it operates. Rather than listing all transmit power variations for every regulatory domain, an example that shows how to configure radio transmit power is provided.

To determine what transmit power is available for a your access point and regulatory domain operate it in, refer to the hardware installation guide for that device. Hardware installation guides are available at cisco.com. Follow these steps to view and download them:


Step 1 Browse to http://www.cisco.com.

Step 2 Click Technical Support & Documentation. A small window appears containing a list of technical support links.

Step 3 Click Technical Support & Documentation. The Technical Support and Documentation page appears.

Step 4 In the Documentation & Tools section, choose Wireless. The Wireless Support Resources page appears.

Step 5 In the Wireless LAN Access section, choose the device you are working with. An introduction page for the device appears.

Step 6 In the Install and Upgrade section, choose Install and Upgrade Guides. The Install and Upgrade Guides page for the device appears.

Step 7 Choose the Hardware Installation Guide for the device. The home page for the guide appears.

Step 8 In the left frame, click Channels and Antenna Settings.


Table 6-1 shows the relationship between mW and dBm.

Table 6-1 Translation between mW and dBm

dBm

-1

2

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

mW

1

2

3

4

5

6

8

10

12

15

20

25

30

40

50

60

80

100

125

150

200

250


Beginning in privileged EXEC mode, follow these steps to set the transmit power on your access point/bridge radio:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

power local cck

{1 | 5 | 10 | 20 | 30 | 50 | 100 |
maximum
}

Set the transmit power for the 802.11g radio to one of the power levels allowed in your regulatory domain. All settings are in mW.

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 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 4 

power local ofdm

{1 | 5 | 10 | 20 | 30 | maximum}

Step 5 

power client

{1 | 5 | 10 | 20 | 30 | 50 | 100 | maximum }

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

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

Step 6 

end

Return to privileged EXEC mode.

Step 7 

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.

Limiting the Power Level for Associated Client Devices

You can also limit the power level on client devices that associate to the access point/bridge. When a client device associates to the access point/bridge, the access point/bridge 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/bridge:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio { slot/port }

Enter interface configuration mode for the radio interface.

Step 3 

power client

These options are available for 802.11g, 2.4-GHz clients (in mW):

[ 1 | 5 | 10 | 20 | 30 | 50 | 100 | maximum ] |

local [cck | ofdm

These cck power level options are available (in mW):

[ 1 | 5 | 10 | 20 | 30 | 50 | 100 | maximum ] |

These ofdm power level options are available (in mW):

[ 1 | 5 | 10 | 20 | 30 | maximum]

Set the maximum power level allowed on client devices that associate to the wireless device.

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

Use the power local command to configure the access point/bridge radio power level You can set Complementary Code Keying (CCK) or Orthogonal Frequency Division Multiplexing power levels.

Step 4 

end

Return to privileged EXEC mode.

Step 5 

copy running-config startup-config

(Optional) Save your entries in the configuration file.


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


Configuring Radio Channel Settings

The default channel setting for the wireless device radios is least congested; at startup, the wireless device scans for and selects the least-congested channel. For most consistent performance after a site survey, however, we recommend that you assign a static channel setting for each access point. The channel settings on the wireless device correspond to the frequencies available in your regulatory domain. See the Cisco Aironet 1300 Series Outdoor Access Point/Bridge Hardware Installation Guide for the frequencies allowed in your domain.

Each 2.4-GHz channel covers 22 MHz. The bandwidth for channels 1, 6, and 11 does not overlap, so you can set up multiple access points in the same vicinity without causing interference. Both 802.11b and 802.11g 2.4-GHz radios use the same channels and frequencies.


Note Too many access points in the same vicinity creates radio congestion that can reduce throughput. A careful site survey can determine the best placement of access points for maximum radio coverage and throughput.


Beginning in privileged EXEC mode, follow these steps to set the wireless device radio channel:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio { slot/port }

Enter interface configuration mode for the radio interface.

Step 3 

channel
frequency | least-congested

Set the default channel for the wireless device radio. Table 6-2 show the channels and frequencies. To search for the least-congested channel on startup, enter least-congested.

Step 4 

end

Return to privileged EXEC mode.

Step 5 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

Table 6-2 shows the available frequencies for the IEEE 802.11g 2.4-GHz radio.

Table 6-2

Channel Identifier
Center Frequency (MHz)
Regulatory Domains
Americas (-A)
EMEA ( -E)
Israel ( -I)
Japan ( -J)
CCK
OFDM
CCK
OFDM
CCK
OFDM
CCK
OFDM

1

2412

X

X

X

X

-

-

X

X

2

2417

X

X

X

X

-

-

X

X

3

2422

X

X

X

X

-

-

X

X

4

2427

X

X

X

X

-

-

X

X

5

2432

X

X

X

X

X

X

X

X

6

2437

X

X

X

X

X

X

X

X

7

2442

X

X

X

X

X

X

X

X

8

2447

X

X

X

X

X

X

X

X

9

2452

X

X

X

X

X

-

X

X

10

2457

X

X

X

X

X

-

X

X

11

2462

X

X

X

X

X

-

X

X

12

2467

-

-

X

X

X

-

X

X

13

2472

-

-

X

X

X

-

X

X

14

2484

-

-

-

-

-

-

-

-


Channels and Available Frequencies for IEEE 802.11g 2.4 GHz Radio

Configuring LBS on Access Points

Use the CLI to configure LBS on your access point/bridge. Beginning in privileged EXEC mode, follow these steps to configure LBS:

 
Command
Purpose
 

configure terminal

Enter global configuration mode.

 

dot11 lbs profile-name

Create an LBS profile for the access point and enter LBS configuration mode.

 

server-address ip-address port port

Enter the IP address of the location server and the port on the server to which the access point sends UDP packets that contain location information.

 

method {rssi}

(Optional) Select the location method that the access point uses when reporting location information to the location server. In this release, rssi (in which the access point measures the location packet's RSSI) is the only option and is also the default.

 

packet-type {short | extended}

(Optional) Select the packet type that the access point accepts from the LBS tag.

short—The access point accepts short location packets from the tag. In short packets, the LBS information is missing from the tag packet's frame body and the packet indicates the tag's transmit channel.

extended—This is the default setting. The access point accepts extended packets from the tag. An extended packet contains two bytes of LBS information in the frame body. If the packet does not contain those two bytes in the frame body, the access point drops the packet.

 

channel-match

(Optional) Specifies that the LBS packet sent by the tag must match the radio channel on which the access point receives the packet. If the channel used by the tag and the channel used by the access point do not match, the access point drops the packet. Channel match is enabled by default.

 

multicast-address mac-address

(Optional) Specifies the multicast address that the tag uses when it sends LBS packets. The default multicast address is 01:40:96:00:00:10.

 

interface dot11 { 0 | 1 }

Specify the radio interface on which this LBS profile is enabled. The 2.4-GHz radio is radio 0, and the 5-GHz radio is radio 1. The profile remains inactive until you enter this command.

 

exit

Return to global configuration mode.

In this example, the profile southside is enabled on the access point's 802.11g radio:

ap# configure terminal
ap(config)# dot11 lbs southside
ap(dot11-lbs)# server-address 10.91.105.90 port 1066
ap(dot11-lbs)# interface dot11 0
ap(dot11-lbs)# exit

Enabling and Disabling World Mode

You can configure the access point/bridge to support 802.11d world mode or Cisco legacy world mode. When you enable world mode, the access point/bridge adds channel carrier set information to its beacon. Client devices with world mode enabled receive the carrier set information and adjust their settings automatically. For example, a client device used primarily in Japan could rely on world mode to adjust its channel and power settings automatically when it travels to Italy and joins a network there. Cisco client devices running firmware version 5.30.17 or later detect whether the access point/bridge is using 802.11d or Cisco legacy world mode and automatically use world mode that matches the mode used by the access point/bridge. World mode is disabled by default.

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/bridge:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

power client

These options are available for 802.11b, 2.4-GHz clients (in mW):

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

These options are available for 802.11g, 2.4-GHz clients (in mW):

{ 1 | 5 | 10 | 20 | 30 | 50 | 100 | maximum}

world-mode
dot11d country_code code
{ both | indoor | outdoor }
|
legacy

Set the maximum power level allowed on client devices that associate to the access point/bridge.

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

Enable world mode.

Enter the dot11d option to enable 802.11d world mode.

When you enter the dot11d option, you must enter a two-character ISO country code (for example, the ISO country code for the United States is US). You can find a list of ISO country codes at the ISO website.

After the country code, you must enter indoor, outdoor, or both to indicate the placement of the access point/bridge.

Enter the legacy option to enable Cisco legacy world mode.

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 command to disable world mode.

Aironet extensions must be enabled for world mode operation. Aironet extensions are enabled by default.

Disabling and Enabling Short Radio Preambles

The radio preamble (sometimes called a header) is a section of data at the head of a packet that contains information that the access point and client devices need when sending and receiving packets. You can set the radio preamble to long or short:

Short—A short preamble improves throughput performance. Cisco Aironet Wireless LAN Client Adapters support short preambles. Early models of Cisco Aironet's Wireless LAN Adapter (PC4800 and PC4800A) require long preambles.

Long—A long preamble ensures compatibility between the access point/bridge and all early models of Cisco Aironet Wireless LAN Adapters (PC4800 and PC4800A). If these client devices do not associate to your access point/bridge, you should use short preambles.

You cannot configure short or long radio preambles on the 5-GHz radio.

Beginning in privileged EXEC mode, follow these steps to disable short radio preambles:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

no preamble-short

Disable short preambles and enable long preambles.

Step 4 

end

Return to privileged EXEC mode.

Step 5 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

Short preambles are enabled by default. Use the preamble-short command to enable short preambles if they are disabled.

Configuring Transmit and Receive Antennas

You can select the antenna the access point/bridge uses to receive and transmit data. There are three options for both the receive and the transmit antenna:

Diversity—This default setting tells the access point/bridge to use the antenna that receives the best signal. If your access point/bridge has two fixed (non-removable) antennas, you should use this setting for both receive and transmit.

Right—If your access point/bridge has removable antennas and you install a high-gain antenna on the access point/bridge's right connector, you should use this setting for both receive and transmit. When you look at the access point/bridge's back panel, the right antenna is on the right.

Left—If your access point/bridge has removable antennas and you install a high-gain antenna on the access point/bridge's left connector, you should use this setting for both receive and transmit. When you look at the access point/bridge's back panel, the left antenna is on the left.


Note The antenna commands are not available for access point/bridges equipped with a captive (internal) antenna.


Beginning in privileged EXEC mode, follow these steps to select the antennas the access point uses to receive and transmit data:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

antenna gain
{<-128 - 128>

Specifies the antenna gain in dB of the connected antennas. Enter the gain in whole numbers (-128 -128 dBi) of the antenna(s) connected to your access point/bridge.

Note This setting does not change the antenna gain, it is used to identify the gain of the installed antenna(s).

Note The antenna gain value is listed on the user document that shipped with your antenna.

Step 4 

antenna receive
{diversity | left | right}

Set the receive antenna to diversity, left, or right.

Note For best performance with two antennas, leave the receive antenna setting at the default setting, diversity. With one antenna, connect the antenna to the right connector and set the diversity to right.

Step 5 

antenna transmit
{diversity | left | right}

Set the transmit antenna to diversity, left, or right.

Note For best performance with two antennas, leave the transmit antenna setting at the default setting, diversity. With one antenna, connect the antenna to the right connector and set the diversity to right.

Step 6 

end

Return to privileged EXEC mode.

Step 7 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

Aironet Extensions


Note Aironet extensions are required by the access point/bridge. They cannot be disabled.


By default, the access point/bridge uses Cisco Aironet 802.11 extensions to detect the capabilities of Cisco Aironet client devices and to support features that require specific interaction between the access point/bridge and associated client devices. Aironet extensions must be enabled to support these features:

Load balancing—The access point/bridge uses Aironet extensions to direct client devices to an access point that provides the best connection to the network based on factors such as number of users, bit error rates, and signal strength.

Message Integrity Check (MIC)—MIC is an additional WEP security feature that prevents attacks on encrypted packets called bit-flip attacks. The MIC, implemented on both the access point/bridge and all associated client devices, adds a few bytes to each packet to make the packets tamper-proof.

Temporal Key Integrity Protocol (TKIP)—TKIP, also known as WEP key hashing, is an additional WEP security feature that defends against an attack on WEP in which the intruder uses an unencrypted segment called the initialization vector (IV) in encrypted packets to calculate the WEP key.

Repeater mode—Aironet extensions must be enabled on repeater access points and on the root access points to which they associate.

World mode—Client devices with world mode enabled receive carrier set information from the access point and adjust their settings automatically.

Limiting the power level on associated client devices—When a client device associates to the access point/bridge, the access point/bridge sends the maximum allowed power level setting to the client.

Configuring the Ethernet Encapsulation Transformation Method

When the access point/bridge receives data packets that are not 802.3 packets, the access point/bridge must format the packets to 802.3 using an encapsulation transformation method. These are the two transformation methods:

802.1H—This method provides optimum performance for Cisco Aironet wireless products. This is the default setting.

RFC1042—Use this setting to ensure interoperability with non-Cisco Aironet wireless equipment. RFC1042 does not provide the interoperability advantages of 802.1H but is used by other manufacturers of wireless equipment.

Beginning in privileged EXEC mode, follow these steps to configure the encapsulation transformation method:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

payload-encapsulation

dot1h | rfc1042

Set the encapsulation transformation method to RFC1042 (rfc1042) or 802.1h (dot1h, the default setting).

Step 4 

end

Return to privileged EXEC mode.

Step 5 

copy running-config startup-config

(Optional) Save your entries in the configuration file.


Note For best performance over your access point/bridge links, adjust the CW-min and CW-max contention window settings to depending on the number of non-root access point/bridges associated to each root access point/bridge. Refer to the "CW-min and CW-max Settings for Point-to-Point and Point-to-Multipoint Bridge Links" section on page 14-11 for instructions on adjusting these settings.


Enabling and Disabling Concatenation

Use the concatenation command to enable packet concatenation on the access point/bridge radio. Using concatenation, the access point/bridge combines multiple packets into one packet to reduce packet overhead and overall latency, which increases transmission efficiency.

Beginning in privileged EXEC mode, follow these steps to enable concatenation and set the maximum length of concatenation.

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

concatenation bytes

(Optional) Bytes specifies a maximum size for concatenation packets in bytes. Enter a value from 1600 to 4000.

Step 4 

end

Return to privileged EXEC mode.

Step 5 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

Configuring the Radio Distance Setting

The distance command is active only when the access point/bridge is configured as a root bridge. Use the command to specify the distance from a root access point/bridge to the non-root access point/bridges with which it communicates. The distance setting adjusts the access point/bridge's time out values to account for the time required for radio signals to travel from access point/bridge to access point/bridge. If more than one non-root access point/bridge communicates with the root access point/bridge, enter the distance from the root access point/bridge to the non-root access point/bridge that is farthest away. Enter a value from 0 to 99 km. You do not need to adjust this setting on non-root access point/bridges.

In installation mode, the default distance setting is 99 km. In other modes, the default distance setting is 0 km.

Beginning in privileged EXEC mode, follow these steps to configure the access point/bridge distance setting:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

distance kilometers

Enter a distance setting from 0 to 99 km.

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 distance command to set the default distance.

Enabling and Disabling Reliable Multicast to Workgroup Bridges

The Reliable multicast messages from the access point to workgroup bridges setting limits reliable delivery of multicast messages to approximately 20 Cisco Aironet Workgroup Bridges that are associated to the access point. The default setting, disabled, reduces the reliability of multicast delivery to allow more workgroup bridges to associate to the access point.

Access points and bridges normally treat workgroup bridges not as client devices but as infrastructure devices, like access points or bridges. Treating a workgroup bridge as an infrastructure device means that the access point reliably delivers multicast packets, including Address Resolution Protocol (ARP) packets, to the workgroup bridge.

The performance cost of reliable multicast delivery—duplication of each multicast packet sent to each workgroup bridge—limits the number of infrastructure devices, including workgroup bridges, that can associate to the access point. To increase beyond 20 the number of workgroup bridges that can maintain a radio link to the access point, the access point must reduce the delivery reliability of multicast packets to workgroup bridges. With reduced reliability, the access point cannot confirm whether multicast packets reach the intended workgroup bridge, so workgroup bridges at the edge of the access point's coverage area might lose IP connectivity. When you treat workgroup bridges as client devices, you increase performance but reduce reliability.


Note This feature is best suited for use with stationary workgroup bridges. Mobile workgroup bridges might encounter spots in the access point's coverage area where they do not receive multicast packets and lose communication with the access point even though they are still associated to it.


A Cisco Aironet Workgroup Bridge provides a wireless LAN connection for up to eight Ethernet-enabled devices.

Beginning in privileged EXEC mode, follow these steps to configure the encapsulation transformation method:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

infrastructure-client

Enable reliable multicast messages to workgroup bridges.

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 command to disable reliable multicast messages to workgroup bridges.

Enabling and Disabling Public Secure Packet Forwarding

Public Secure Packet Forwarding (PSPF) prevents client devices associated to an access point from inadvertently sharing files or communicating with other client devices associated to the access point. It provides Internet access to client devices without providing other capabilities of a LAN. This feature is useful for public wireless networks like those installed in airports or on college campuses.


Note To prevent communication between clients associated to different access points, you must set up protected ports on the switch to which your access points are connected. See the Configuring Protected Ports for instructions on setting up protected ports.


To enable and disable PSPF using CLI commands on your access point, you use bridge groups. You can find a detailed explanation of bridge groups and instructions for implementing them in this document:

Cisco IOS Bridging and IBM Networking Configuration Guide, Release 12.2. Click this link to browse to the Configuring Transparent Bridging chapter:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fibm_c/bcfpart1/bcftb.htm

You can also enable and disable PSPF using the web-browser interface. The PSPF setting is on the Radio Settings pages.

PSPF is disabled by default. Beginning in privileged EXEC mode, follow these steps to enable PSPF:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

bridge-group group port-protected

Enable PSPF.

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 command to disable PSPF.

Configuring Protected Ports

To prevent communication between client devices associated to different access points on your wireless LAN, you must set up protected ports on the switch to which your access points are connected.

Beginning in privileged EXEC mode, follow these steps to define a port on your switch as a protected port:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface interface-id

Enter interface configuration mode, and enter the type and number of the switchport interface to configure, such as gigabitethernet0/1.

Step 3 

switchport protected

Configure the interface to be a protected port.

Step 4 

end

Return to privileged EXEC mode.

Step 5 

show interfaces interface-id switchport

Verify your entries.

Step 6 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

To disable protected port, use the no switchport protected interface configuration command.

For detailed information on protected ports and port blocking, refer to the "Configuring Port-Based Traffic Control" chapter in the Catalyst 3550 Multilayer Switch Software Configuration Guide, 12.1(12c)EA1. Click this link to browse to that guide: http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/release/12.1_12c_ea1/configuration/guide/3550scg.html

Enabling Short Slot Time

You can increase throughput on the 802.11g, 2.4-GHz radio by enabling short slot time. Reducing the slot time from the standard 20 microseconds to the 9-microsecond short slot time decreases the overall backoff, which increases throughput. Backoff, which is a multiple of the slot time, is the random length of time that a station waits before sending a packet on the LAN.

Many 802.11g radios support short slot time, but some do not. When you enable short slot time, the wireless device uses the short slot time only when all clients associated to the 802.11g, 2.4-GHz radio support short slot time.

In radio interface mode, enter this command to enable short slot time:

ap(config-if)# slot-time-short 

Enter no slot-time-short to disable short slot time.

Configuring the Beacon Period and the DTIM

The beacon period is the amount of time between access point beacons in Kilomicroseconds. One Kµsec equals 1,024 microseconds. The Data Beacon Rate, always a multiple of the beacon period, determines how often the beacon contains a delivery traffic indication message (DTIM). The DTIM tells power-save client devices that a packet is waiting for them.

For example, if the beacon period is set at 100, its default setting, and the data beacon rate is set at 2, its default setting, then the wireless device sends a beacon containing a DTIM every 200 Kµsecs.

Beginning in privileged EXEC mode, follow these steps to configure the beacon period:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

beacon period value

Set the beacon period. Enter a value between 20 and 4000 Kusecs.

Step 4 

beacon dtim-period value

Set the DTIM. Enter a value between 1 and 100 Kilomicroseconds.

Step 5 

end

Return to privileged EXEC mode.

Step 6 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

Configure RTS Threshold and Retries

The RTS threshold determines the packet size at which the access point/bridge issues a request to send (RTS) before sending the packet. A low RTS Threshold setting can be useful in areas where many client devices are associating with the access point/bridge, or in areas where the clients are far apart and can detect only the access point/bridge and not each other. You can enter a setting ranging from 0 to 23472347 bytes.


Note When concatenation is enabled, the RTS and fragment thresholds are set to 4000. Changing them to a lower value may degrade access point/bridge performance.


Maximum RTS Retries is the maximum number of times the access point/bridge issues an RTS before stopping the attempt to send the packet over the radio. Enter a value from 1 to 128.

The default RTS threshold is 2312, and the default maximum RTS retries setting is 32. Beginning in privileged EXEC mode, follow these steps to configure the RTS threshold and maximum RTS retries:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

rts threshold value

Set the RTS threshold. Enter a setting from 0 to 4000.

Step 4 

rts retries value

Set the maximum RTS retries. Enter a setting from 1 to 128.

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 command to reset the RTS settings to defaults.

Configuring the Maximum Data Retries

The maximum data retries setting determines the number of attempts the access point/bridge makes to send a packet before giving up and dropping the packet.

The default setting is 32. Beginning in privileged EXEC mode, follow these steps to configure the maximum data retries:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

packet retries value | drop-packet

Set the maximum data retries. Enter a setting from 1 to 128.

Use the drop-packet command to maintain association and drop the packets when the maximum retry value is reached.

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 command to reset the setting to defaults.

Configuring the Fragmentation Threshold

The fragmentation threshold determines the size at which packets are fragmented (sent as several pieces instead of as one block). Use a low setting in areas where communication is poor or where there is a great deal of radio interference.


Note When concatenation is enabled, the RTS and fragment thresholds are set to 4000. Changing them to a lower value may degrade access point/bridge performance.


The default setting is 2338 bytes. Beginning in privileged EXEC mode, follow these steps to configure the fragmentation threshold:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

fragment-threshold value

Set the fragmentation threshold. Enter a setting from 256 to 2346 bytes for the 2.4-GHz radio.

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 command to reset the setting to defaults.

Setting the Root Parent Timeout Value

Use the parent timeout command to define the amount of time that a non-root access point/bridge or workgroup bridge tries to associate with a parent access point. The command defines how long the access point/bridge or workgroup bridge attempts to associate with a parent in the parent list. If an association is not made within the timeout value, another acceptable parent is used. You set up the parent list using the parent command. With the timeout disabled, the parent must come from the parent list.

Beginning in privileged EXEC mode, follow these steps to configure the root parent timeout value:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

parent timeout seconds

The seconds value specifies the amount of time in seconds the non-root access point/bridge or workgroup bridge attempts to associate with a specified parent. Enter a value between 0 and 65535 seconds.

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 command to reset the setting to defaults.

Configuring the Root Parent MAC

Use the parent command to add a parent to a list of valid parent access points. The command adds a parent to the list of valid parent access points. You can use this command multiple times to define up to four valid parents. A repeater access point operates best when it is configured to associate with specific root access points that are connected to the wired LAN.

Beginning in privileged EXEC mode, follow these steps to configure the fragmentation threshold:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio 0

Enter interface configuration mode for the radio interface.

Step 3 

parent 1-4 mac-address

The value 1-4 specifies the parent root access point number. mac-address specifies the MAC address of a parent access point (in xxxx.xxxx.xxxx format).

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 command to reset the setting to defaults.

Performing a Carrier Busy Test

You can perform a carrier busy test to check the radio activity on access point/bridge channels. During the carrier busy test, the access point/bridge drops all associations with wireless networking devices for around 4 seconds while it conducts the carrier test and then displays the test results.

In privileged EXEC mode, enter this command to perform a carrier busy test:

dot11 interface-number carrier busy

For interface-number, enter dot11radio 0 to run the test on the 2.4-GHz radio, or enter dot11radio 1 to run the test on the 5-GHz radio.

Use the show dot11 carrier busy command to re-display the carrier busy test results.