The access point is shipped with an autonomous image and recovery image on the access point’s flash. The default mode is autonomous; however, the access point can be upgraded to operate in Cisco Unified Wireless mode.

Each mode is described below:

• Autonomous mode—supports standalone network configurations, where all configuration settings are maintained locally on the wireless device. Each autonomous device can load its starting configuration independently, and still operate in a cohesive fashion on the network.
• Cisco Unified Wireless mode—operates in conjunction with a Cisco Unified Wireless LAN controller, where all configuration information is maintained within the controller. In the Cisco Unified Wireless LAN architecture, wireless devices operate in the lightweight mode using Leightweight Access Point Protocol (LWAPP), (as opposed to autonomous mode). The lightweight access point, or wireless device, has no configuration until it associates to a controller. The configuration on the wireless device can be modified by the controller only when the networking is up and running. The controller manages the wireless device configuration, firmware, and control transactions such as 802.1x authentication. All wireless traffic is tunneled through the controller.

For more information about Cisco Unified Wireless mode, see http:/​/​www.cisco.com/​en/​US/​prod/​collateral/​wireless/​ps5679/​ps6548/​prod_​white_​paper0900aecd804f19e3_​ps6305_​Products_​White_​Paper.html .

The wireless device runs its own version of Cisco IOS software that is separate from the Cisco IOS software operating on the router. You can configure and monitor the access point with several different tools:

• Cisco IOS software CLI
• Simple Network Management Protocol (SNMP)
• Web-browser Interface

Note	Avoid using the CLI and the web-browser tools concurrently. If you configure the wireless device using the CLI, the web-browser interface may display an inaccurate interpretation of the configuration.

Use the interface dot11radio command from global configuration mode to place the wireless device into the radio configuration mode. Network Configuration Examples

Set up the access point role in any of these common wireless network configurations. The access point default configuration is as a root unit connected to a wired LAN or as the central unit in an all-wireless network. Access points can also be configured as bridges and workgroup bridges. These roles require specific configurations, as defined in the following examples.

Note	Before you configure the wireless settings in the router’s setup, you must follow step 1 and 2 to open a session between the router and the access point.

Note	Step 1 and 2 are not required in releases prior to Release 15.5(03)M06.

Enter the following commands in global configuration mode on the router’s Cisco IOS command-line interface (CLI).

1.    line line number


2.    transport input all


3.    interface wlan-ap0


4.    ip address subnet mask


5.    no shut


6.    interface vlan1


7.    ip address subnet mask


8.    exit


9.    exit


10.    service-module wlan-ap 0 session

Router(config)# line 2

Router(config)# transport input all

Router(config)# interface wlan-ap0

The wlan-ap 0 interface is used for managing the embedded AP. Please use the service-module wlan-ap 0 session command to console into the embedded AP.

Router(config-if)# ip address 10.21.0.20 255.255.255.0

Router(config-if)# no shut

Router(config-if)# interface vlan1

Router(config-if)# ip address 10.10.0.30 255.255.255.0

Router(config-if)# exit

Router(config)#

Router(config)# exit

Router#

Router# service-module wlan-ap0 session
Trying 10.21.0.20, 2002 ... Open
ap>

Tip	To create a Cisco IOS software alias for the console to session into the wireless device, enter the alias exec dot11radio service-module wlan-ap 0 session command at the EXEC prompt. After entering this command, you utomatically skip to the dot11 radio level in the Cisco IOS software.

Note	If you are configuring the wireless device for the first time, you must start a configuration session between the access point and the router before you attempt to configure the basic wireless settings. See the Starting a Wireless Configuration Session.

Configure the wireless device with either of the following tools, depending on the software you are using:

• Cisco IOS Command Line Interface—Autonomous software
• Cisco Express Setup—Unified Software

Note

To upgrade to Unified mode from the Autonomous mode, see Upgrading to Cisco Unified Software for upgrade instructions. After upgrading to Cisco Unified Wireless software, use the web-browser tool to configure the device: http:/​/​cisco.com/​en/​US/​docs/​wireless/​access_point/​12.4_10b_JA/​configuration/​guide/​scg12410b-chap2-gui.html

To configure the Unified wireless device, use the web-browser tool and perform these steps

1. Establish a console connection to the wireless device and get the Bridge-Group Virtual Interface (BVI) IP address by entering the show interface bvi1 Cisco IOS command.
2. Open a browser window, and enter the BVI IP address in the browser-window address line. Press Enter. An Enter Network Password window appears.
3. Enter your username. Cisco is the default user name.
4. Enter the wireless device password. Cisco is the default password. The Summary Status page appears. For details about using the web-browser configuration page, see the following URL:

   http:/​/​cisco.com/​en/​US/​docs/​wireless/​access_point/​12.4_10b_JA/​configuration/​guide/​scg12410b-chap4-first.html#wp1103336

To configure the Autonomous wireless device, use the Cisco IOS CLI tool and perform these tasks:

In hot standby mode, an access point is designated as a backup for another access point. The standby access point is placed near the access point that it monitors and is configured exactly like the monitored access point. The standby access point associates with the monitored access point as a client and sends Internet Access Point Protocol (IAPP) queries to the monitored access point through the Ethernet and radio ports. If the monitored access point fails to respond, the standby access point comes online and takes the monitored access point’s place in the network.

Except for the IP address, the standby access point’s settings should be identical to the settings on the monitored access point. If the monitored access point goes off line and the standby access point takes its place in the network, matching settings ensure that client devices can switch easily to the standby access point. For more information, see Hot Standby Access Points at:

http:/​/​www.cisco.com/​en/​US/​docs/​routers/​access/​wireless/​software/​guide/​RolesHotStandby.html.

To run the access point in Cisco Unified mode, upgrade the software by performing the following procedures:

Perform the tasks in the following sections to prepare for the upgrade:

To upgrade the autonomous software to Cisco Unified software, follow these steps:

1. To change the access point boot image to a Cisco Unified upgrade image (also known as a recovery image ), use the service-module wlan-ap 0 bootimage unified command, in global configuration mode.

   Router# conf terminal
   Router(config)# service-module wlan-ap 0 bootimage unified
   Router(config)# end
   

   Note	If the service-module wlan-ap 0 bootimage unified command does not work successfully, check whether the software license is still eligible.

   Note	To identify the access point’s boot image path, use the show boot command in privileged EXEC mode on the access point console.

2. To perform a graceful shutdown and reboot of the access point to complete the upgrade process, use the service-module wlan-ap 0 reload command in global configuration mode. Establish a session into the access point, and monitor the upgrade process.

   Note	See the Cisco Express Setup for details about using the GUI configuration page to set up the wireless device settings.

If the access point fails to upgrade from autonomous to Unified software, perform the following actions:

• Check to ensure the autonomous access point does not have the static IP address configured on the BVI interface before you boot the recovery image.
• Ping between the router/access point and the WLC to confirm communication.
• Check that the access point and WLC clock (time and date) are set correctly.

The access point may attempt to boot and fail or may become stuck in the recovery mode and fail to upgrade to the Unified software. If either one of this occurs, use the service-module wlan-ap0 reset bootloader command to return the access point to the bootloader for manual image recovery.

To reset the access point boot to the last autonomous image, use the service-module wlan-ap0 bootimage autonomous command in global configuration mode. To reload the access point with the autonomous software image, use the service-module wlan-ap 0 reload command.

To recover the image on the access point, use the service-module wlan-ap0 reset bootloader command in global configuration mode. This command returns the access point to the bootloader for manual image recovery.

Caution

Use this command with caution. It does not provide an orderly shutdown and consequently may impact file operations that are in progress. Use this command only to recover from a shutdown or a failed state.

See the following documentation for additional autonomous and unified configuration procedures:

The wireless device radios are disabled by default.

Note	You must create a service set identifier (SSID) before you can enable the radio interface.

To enable the access point radio, follow these steps, beginning in privileged EXEC mode:

1.    configure terminal


2.    dot11 ssid ssid


3.    interface dot11radio {0}


4.    ssid ssid


5.    no shutdown


6.    end


7.    copy running-config startup-config

The wirless device radio performs the following roles in the wireless network:

• Access point
• Access point (fallback to radioP shutdown)
• Root bridge
• Non-root bridge
• Root bridge with wireless clients
• Non-root bridge without wireless clients

You can also configure a fallback role for root access points. The wireless device automatically assumes the fallback role when its Ethernet port is disabled or disconnected from the wired LAN. The default fallback role for Cisco ISR wireless devices is shutdown, that is the wireless device shuts down its radio and disassociates all client devices.

The dual-radio fallback features allows you to configure access points so that if the non-root bridge link connecting the access point to the network infrastructure goes down, the root access point link through which a client connects to the access point shut down. Shutting down the root access point link causes the client to roam to another access point. Without this feature, the client remains connected to the access point, but won't be able to send or receive data from the network.

You can configure dual-radio fallback in three ways:

You use the data rate settings to choose the data rates that the wireless device uses for data transmission. The rates are expressed in megabits per second (Mb/s). The wireless device always attempts to transmit at the highest data rate set to basic, also known as required on the browser-based interface. If there are obstacles or interference, the wireless device steps down to the highest rate that allows data transmission. You can set each data rate to one of three states:

• Basic (the GUI labels Basic rates as Required)—Allows transmission at this rate for all packets, both unicast and multicast. At least one of the data rates of the wireless device must be set to basic.
• Enabled—The wireless device transmits only unicast packets at this rate; multicast packets are sent at one of the data rates set to basic.
• Disabled—The wireless device 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 an access point to serve client devices operating at specific data rates. For example, to set the 2.4-GHz radio for 11 Mb/s service only, set the 11-Mb/s 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 Mb/s, 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. To set the 5-GHz radio for 54-Mb/s service only, set the 54-Mb/s rate to basic, and set the other data rates to disabled.

You can configure the wireless device to set the data rates automatically to optimize either the range or the throughput. When you enter range for the data rate setting, the wireless device sets the 1-Mb/s rate to basic and sets the other rates to enabled. The range setting allows the access point to extend the coverage area by compromising on the data rate. Therefore, if you have a client that cannot connect to the access point although other clients can, the client might not be within the coverage area of the access point. In such a case, using the range option will help extend the coverage area, and the client may be able to connect to the access point.

Typically, the trade-off is between throughput and range. When the signal degrades (possibly due to distance from the access point), the rates renegotiate in order to maintain the link (but at a lower data rate). A link that is configured for a higher throughput simply drops when the signal degrades enough that it no longer sustains a configured high data rate, or the link roams to another access point with sufficient coverage, if one is available. The balance between the two (throughput vs. range) is a design decision that must be made based on resources available to the wireless project, the type of traffic the users will be passing, the service level desired, and as always, the quality of the RF environment. When you enter throughput for the data rate setting, the wireless device sets all four data rates to basic.

Note

When a wireless network has a mixed environment of 802.11b clients and 802.11g clients, make sure that data rates 1, 2, 5.5, and 11 Mb/s are set to required (basic) and that all other data rates are set to enable. The 802.11b adapters do not recognize the 54 Mb/s data rate and do not operate if data rates higher than 11 Mb/s are set to required on the connecting access point.

Modulation coding scheme (MCS) is a specification of PHY parameters consisting of modulation order (binary phase shift keying [BPSK], quaternary phase shift keying [QPSK], 16-quadrature amplitude modulation [16-QAM], 64-QAM) and forward error correction (FEC) code rate (1/2, 2/3, 3/4, 5/6). MCS is used in the wireless device 802.11n radios, which define 32 symmetrical settings (8 per spatial stream):

• MCS 0–7
• MCS 8–15
• MCS 16–23
• MCS 24–31

The wireless device supports MCS 0–15. High-throughput clients support at least MCS 0–7.

MCS is an important setting because it provides for potentially greater throughput. High-throughput data rates are a function of MCS, bandwidth, and guard interval. The 802.11a, b, and g radios use 20-MHz channel widths. Table 1 shows potential data rated based on MCS, guard interval, and channel width.

1.    configure terminal


2.    interface dot11radio {0}


3.    power local


4.    end


5.    copy running-config startup-config

Router# configure terminal

These options are available for the 2.4-GHz 802.11n radio (in dBm):

{8 | 9| 11 | 14 | 15 | 17 | maximum}

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 the 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 access point hardware installation guide for the frequencies allowed in your domain.

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

The 5-GHz radio operates on 8 channels from 5180 to 5320 MHz, up to 27 channels from 5170 to 5850 MHz depending on regulatory domain. Each channel covers 20 MHz, and the bands for the channels overlap slightly. For best performance, use channels that are not adjacent (use channels 44 and 46, for example) for radios that are close to each other.

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

The 802.11n standard allows both 20-MHz and 40-Mhz channel widths consisting of two contiguous non-overlapping channels (for example, 2.4-GHz channels 1 and 6)

One of the 20-MHz channels is called the control channel. Legacy clients and 20-MHz high-throughput clients use the control channel. Only beacons can be sent on this channel. The other 20-MHz channel is called the extension channel. The 40-MHz stations may use this channel and the control channel simultaneously.

A 40-MHz channel is specified as a channel and extension, such as 1,1. In this example, the control channel is channel 1 and the extension channel is above it.

You can configure the wireless device to support 802.11d world mode, Cisco legacy world mode, or world mode roaming. When you enable world mode, the wireless device 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 detect whether the wireless device is using 802.11d or Cisco legacy world mode and automatically use the world mode that matches the mode used by the wireless device.

You can also configure world mode to be always on. In this configuration, the access point essentially roams between countries and changes its settings as required. World mode is disabled by default.

The radio preamble (sometimes called a header) is a section of data at the head of a packet that contains information that the wireless device 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.
• Long—A long preamble ensures compatibility between the wireless device and all early models of Cisco Aironet Wireless LAN Adapters. If these client devices do not associate to the wireless devices, you should use short preambles.

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

You can select the antenna that the wireless device uses to receive and transmit data. There are four options for both the receive antenna and the transmit antenna:

• Gain—Sets the resultant antenna gain in decibels (dB).
• Diversity—This default setting tells the wireless device to use the antenna that receives the best signal. If the wireless device has two fixed (non-removable) antennas, you should use this setting for both receive and transmit.
• Right—If the wireless device has removable antennas and you install a high-gain antenna on the wireless device’s right connector, you should use this setting for both receive and transmit. When you look at the wireless device’s back panel, the right antenna is on the right.
• Left—If the wireless device has removable antennas and you install a high-gain antenna on the wireless device’s left connector, you should use this setting for both receive and transmit. When you look at the wireless device’s back panel, the left antenna is on the left.

See the following section for information on configuring transmit and receive antennas:

By default, the wireless device 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 wireless device and associated client devices. Aironet extensions must be enabled to support these features:

• Load balancing—The wireless device uses Aironet extensions to direct client devices to an access point that provides the best connection to the network on the basis of such factors 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 the wireless device and all associated client devices, adds a few bytes to each packet to make the packets tamper-proof.
• Load balancing—The wireless device uses Aironet extensions to direct client devices to an access point that provides the best connection to the network on the basis of such factors as number of users, bit error rates, and signal strength.
• Cisco Key Integrity Protocol (CKIP)—Cisco’s WEP key permutation technique is based on an early algorithm presented by the IEEE 802.11i security task group. The standards-based algorithm, Temporal Key Integrity Protocol (TKIP), does not require Aironet extensions to be enabled.
• World mode (legacy only)—Client devices with legacy world mode enabled receive carrier set information from the wireless device and adjust their settings automatically. Aironet extensions are not required for 802.11d world mode operation.
• Limiting the power level on associated client devices—When a client device associates to the wireless device, the wireless device sends the maximum allowed power level setting to the client.

Disabling Aironet extensions disables the features listed above, but it sometimes improves the ability of non-Cisco client devices to associate to the wireless device.

When the wireless device receives data packets that are not 802.3 packets, the wireless device must format the packets to 802.3 by using an encapsulation transformation method. These are the two transformation methods:

• 802.1H—This method provides optimum performance for Cisco wireless products.
• RFC 1042—Use this setting to ensure interoperability with non-Cisco wireless equipment. RFC1042 does not provide the interoperability advantages of 802.1H but is used by other manufacturers of wireless equipment.

For information on how to configure the ethernet encapsulation transformation method, see the following section:

Public Secure Packet Forwarding (PSPF) prevents client devices that are associated to an access point from inadvertently sharing files or communicating with other client devices that are associated to the access point. PSPF 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 the wireless devices are connected. See the Related Documentation for instructions on setting up protected ports.

To enable and disable PSPF using CLI commands on the wireless device, you use bridge groups. For a detailed explanation of bridge groups and instructions for implementing them, see the following link:

http:/​/​www.cisco.com/​en/​US/​docs/​ios/​12_2/​ibm/​configuration/​guide/​bcftb_​ps1835_​TSD_​Products_​Configuration_​Guide_​Chapter.html

The beacon period is the amount of time between access point beacons in kilomicroseconds (Kmicrosecs). One Kmicrosec 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 if the data beacon rate is set at 2, its default setting, then the wireless device sends a beacon containing a DTIM every 200 Kmicrosecs.

The default beacon period is 100, and the default DTIM is 2.

See the following section for information on configuring beacon period and DTIM:

The request to send (RTS) threshold determines the packet size at which the wireless device issues an RTS before sending the packet. A low RTS threshold setting can be useful in areas where many client devices are associating with the wireless device, or in areas where the clients are far apart and can detect only the wireless device and not detect each other. You can enter a setting ranging from 0 to 2347 bytes.

The maximum RTS retries is the maximum number of times the wireless device 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 2347 for all access points and bridges, and the default maximum RTS retries setting is 32.

The maximum data retries setting determines the number of attempts that the wireless device makes to send a packet before it drops the packet. The default setting is 32.

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. The default setting is 2346 bytes.

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.

Short slot time is supported only on the 802.11g 2.4-GHz radio. Short slot time is disabled by default.

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

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

Use the no form of the short-slot-time command to disable short slot time.

You can perform a carrier busy test to check the radio activity on wireless channels. During the carrier busy test, the wireless device drops all associations with wireless networking devices for 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

Use the show dot11 carrier busy command to redisplay the carrier busy test results.

You can improve the quality of VoIP packet handling per radio on access points by enhancing 802.11 MAC behavior for lower latency for the class of service (CoS) 5 (Video) and CoS 6 (Voice) user priorities.

To configure VoIP packet handling on an access point, follow these steps:

1. Using a browser, log in to the access point.
2. Click Services in the task menu on the left side of the web-browser interface.
3. When the list of Services expands, click Stream.

   The Stream page appears.

4. Click the tab for the radio to configure.
5. For both CoS 5 (Video) and CoS 6 (Voice) user priorities, choose Low Latency from the Packet Handling drop-down menu, and enter a value for maximum retries for packet discard in the corresponding field.

   The default value for maximum retries is 3 for the Low Latency setting. This value indicates how many times the access point will try to retrieve a lost packet before discarding it.

   Figure 3. Packet Handling Configuration
   
   

   Note	You may also configure the CoS 4 (Controlled Load) user priority and its maximum retries value.

6. Click Apply.

This section provides information about performing the following tasks to secure access to the wireless device: