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Radio Resource Management
The Radio Resource Management (RRM) software embedded in the Cisco Wireless LAN Controller acts as a built-in RF engineer to consistently provide real-time RF management of your wireless network. RRM enables Cisco WLCs to continually monitor their associated lightweight access points for the following information:
Traffic load—The total bandwidth used for transmitting and receiving traffic. It enables wireless LAN managers to track and plan network growth ahead of client demand.
Interference—The amount of traffic coming from other 802.11 sources.
Noise—The amount of non-802.11 traffic that is interfering with the currently assigned channel.
Coverage—The received signal strength (RSSI) and signal-to-noise ratio (SNR) for all connected clients.
Using this information, RRM can periodically reconfigure the 802.11 RF network for best efficiency. To do this, RRM performs these functions:
RRM automatically detects and configures new Cisco WLCs and lightweight access points as they are added to the network. It then automatically adjusts associated and nearby lightweight access points to optimize coverage and capacity.
Lightweight access points can simultaneously scan all valid 802.11a/b/g channels for the country of operation as well as for channels available in other locations. The access points go “off-channel” for a period not greater than 60 ms to monitor these channels for noise and interference. Packets collected during this time are analyzed to detect rogue access points, rogue clients, ad-hoc clients, and interfering access points.
Note | In the presence of voice traffic (in the last 100 ms), the access points defer off-channel measurements. |
Each access point spends only 0.2 percent of its time off-channel. This activity is distributed across all access points so that adjacent access points are not scanning at the same time, which could adversely affect wireless LAN performance.
RRM produces a network with optimal capacity, performance, and reliability. It frees you from having to continually monitor the network for noise and interference problems, which can be transient and difficult to troubleshoot. RRM ensures that clients enjoy a seamless, trouble-free connection throughout the Cisco unified wireless network.
RRM uses separate monitoring and control for each deployed network: 802.11a and 802.11b/g. The RRM algorithms run separately for each radio type (802.11a and 802.11b/g). RRM uses both measurements and algorithms. RRM measurements can be adjusted using monitor intervals, but they cannot be disabled. RRM algorithms are enabled automatically but can be disabled by statically configuring channel and power assignment. The RRM algorithms run at a specified updated interval, which is 600 seconds by default.
The controller’s preconfigured RRM settings are optimized for most deployments. However, you can modify the controller’s RRM configuration parameters at any time through either the GUI or the CLI.
You can configure these parameters on controllers that are part of an RF group or on controllers that are not part of an RF group.
The RRM parameters should be set to the same values on every controller in an RF group. The RF group leader can change as a result of controller reboots or depending on which radios hear each other. If the RRM parameters are not identical for all RF group members, varying results can occur when the group leader changes.
Using the controller GUI, you can configure the following RRM parameters: RF group mode, transmit power control, dynamic channel assignment, coverage hole detection, profile thresholds, monitoring channels, and monitor intervals.
The OEAP 600 series access points do not support RRM. The radios for the 600 series OEAP access points are controlled through the local GUI of the 600 series access points and not through the Cisco WLC. Attempting to control the spectrum channel or power, or disabling the radios through the Cisco WLC will fail to have any effect on the 600 series OEAP.
To see 802.11a and 802.11b/g RRM settings, use these commands:
show advanced {802.11a | 802.11b} ?
where ? is one of the following:
channel—Shows the channel assignment configuration and statistics.
coverage—Shows the coverage hole detection configuration and statistics.
profile {global | Cisco_AP}—Shows the access point performance profiles.
receiver—Shows the 802.11a or 802.11b/g receiver configuration and statistics.
summary—Shows the configuration and statistics of the 802.11a or 802.11b/g access points.
txpower—Shows the transmit power assignment configuration and statistics.
Use these commands to troubleshoot and verify RRM behavior:
RF Groups
An RF group is a logical collection of Cisco WLCs that coordinate to perform RRM in a globally optimized manner to perform network calculations on a per-radio basis. An RF group exists for each 802.11 network type. Clustering Cisco WLCs into a single RF group enables the RRM algorithms to scale beyond the capabilities of a single Cisco WLC.
RF grouping runs between MCs.
Lightweight access points periodically send out neighbor messages over the air. Access points using the the same RF group name validate messages from each other.
When access points on different Cisco WLCs hear validated neighbor messages at a signal strength of –80 dBm or stronger, the Cisco WLCs dynamically form an RF neighborhood in auto mode. In static mode, the leader is manually selected and the members are added to the RF Group. To know more about RF Group modes, see “RF Group Leader” section.
Note | RF groups and mobility groups are similar in that they both define clusters of Cisco WLCs, but they are different in terms of their use. An RF group facilitates scalable, system-wide dynamic RF management while a mobility group facilitates scalable, system-wide mobility and Cisco WLC redundancy. |
Starting in the 7.0.116.0 release, the RF Group Leader can be configured in two ways as follows:
Auto Mode—In this mode, the members of an RF group elect an RF group leader to maintain a “master” power and channel scheme for the group. The RF grouping algorithm dynamically chooses the RF group leader and ensures that an RF group leader is always present. Group leader assignments can and do change (for instance, if the current RF group leader becomes inoperable or RF group members experience major changes).
Static Mode—In this mode, the user selects a Cisco WLC as an RF group leader manually. In this mode, the leader and the members are manually configured and fixed. If the members are unable to join the RF group, the reason is indicated. The leader tries to establish a connection with a member every one minute if the member has not joined in the previous attempt.
The RF group leader analyzes real-time radio data collected by the system, calculates the power and channel assignments, and sends them to each of the Cisco WLCs in the RF group. The RRM algorithms ensure system-wide stability, and restrain channel and power scheme changes to the appropriate local RF neighborhoods.
In Cisco WLC software releases prior to 6.0, the dynamic channel assignment (DCA) search algorithm attempts to find a good channel plan for the radios associated to Cisco WLCs in the RF group, but it does not adopt a new channel plan unless it is considerably better than the current plan. The channel metric of the worst radio in both plans determines which plan is adopted. Using the worst-performing radio as the single criterion for adopting a new channel plan can result in pinning or cascading problems.
Pinning occurs when the algorithm could find a better channel plan for some of the radios in an RF group but is prevented from pursuing such a channel plan change because the worst radio in the network does not have any better channel options. The worst radio in the RF group could potentially prevent other radios in the group from seeking better channel plans. The larger the network, the more likely pinning becomes.
Cascading occurs when one radio’s channel change results in successive channel changes to optimize the remaining radios in the RF neighborhood. Optimizing these radios could lead to their neighbors and their neighbors’ neighbors having a suboptimal channel plan and triggering their channel optimization. This effect could propagate across multiple floors or even multiple buildings, if all the access point radios belong to the same RF group. This change results in considerable client confusion and network instability.
The main cause of both pinning and cascading is the way in which the search for a new channel plan is performed and that any potential channel plan changes are controlled by the RF circumstances of a single radio. In Cisco WLC software release 6.0, the DCA algorithm has been redesigned to prevent both pinning and cascading. The following changes have been implemented:
Multiple local searches—The DCA search algorithm performs multiple local searches initiated by different radios in the same DCA run rather than performing a single global search driven by a single radio. This change addresses both pinning and cascading while maintaining the desired flexibility and adaptability of DCA and without jeopardizing stability.
Multiple Channel Plan Change Initiators (CPCIs)—Previously, the single worst radio was the sole initiator of a channel plan change. Now each radio in the RF group is evaluated and prioritized as a potential initiator. Intelligent randomization of the resulting list ensures that every radio is eventually evaluated, which eliminates the potential for pinning.
Limiting the propagation of channel plan changes (Localization)—For each CPCI radio, the DCA algorithm performs a local search for a better channel plan, but only the CPCI radio itself and its one-hop neighboring access points are actually allowed to change their current transmit channels. The impact of an access point triggering a channel plan change is felt only to within two RF hops from that access point, and the actual channel plan changes are confined to within a one-hop RF neighborhood. Because this limitation applies across all CPCI radios, cascading cannot occur.
Non-RSSI-based cumulative cost metric—A cumulative cost metric measures how well an entire region, neighborhood, or network performs with respect to a given channel plan. The individual cost metrics of all access points in that area are considered in order to provide an overall understanding of the channel plan’s quality. These metrics ensure that the improvement or deterioration of each single radio is factored into any channel plan change. The objective is to prevent channel plan changes in which a single radio improves but at the expense of multiple other radios experiencing a considerable performance decline.
The RRM algorithms run at a specified updated interval, which is 600 seconds by default. Between update intervals, the RF group leader sends keepalive messages to each of the RF group members and collects real-time RF data.
Note | Several monitoring intervals are also available. See the Configuring RRM section for details. |
A Cisco WLC is configured in an RF group name, which is sent to all access points joined to the Cisco WLC and used by the access points as the shared secret for generating the hashed MIC in the neighbor messages. To create an RF group, you configure all of the Cisco WLCs to be included in the group with the same RF group name.
If there is any possibility that an access point joined to a Cisco WLC may hear RF transmissions from an access point on a different Cisco WLC, you should configure the Cisco WLCs with the same RF group name. If RF transmissions between access points can be heard, then system-wide RRM is recommended to avoid 802.11 interference and contention as much as possible.
Controller software supports up to 20 controllers and 6000 access points in an RF group.
The RF group members are added based on the following criteria:
Maximum number of APs Supported: The maximum limit for the number of access points in an RF group is 6000. The number of access points supported is determined by the number of APs licensed to operate on the controller.
Twenty controllers: Only 20 controllers (including the leader) can be part of an RF group if the sum of the access points of all controllers combined is less than or equal to the upper access point limit.
8500 | 7500 | 5500 | WiSM2 | |
---|---|---|---|---|
Maximum APs per RRM Group | 6000 | 6000 | 1000 | 2000 |
Maximum AP Groups | 6000 | 6000 | 500 | 500 |
This section describes how to configure RF groups through either the GUI or the CLI.
Note | The RF group name is generally set at deployment time through the Startup Wizard. However, you can change it as necessary. |
Note | When the multiple-country feature is being used, all Cisco WLCs intended to join the same RF group must be configured with the same set of countries, configured in the same order. |
Note | You can also configure RF groups using the Cisco Prime Infrastructure. |
Step 1 | Choose Controller > General to open the General page. |
Step 2 | Enter a name for the RF group in the RF-Network Name text box. The name can contain up to 19 ASCII characters. |
Step 3 | Click Apply to commit your changes. |
Step 4 | Click Save Configuration to save your changes. |
Step 5 | Repeat this procedure for each controller that you want to include in the RF group. |
Step 1 | Create an RF group by entering the config network rf-network-name name command:
| ||
Step 2 | See the RF group by entering the show network command. | ||
Step 3 | Save your settings by entering the save config command. | ||
Step 4 | Repeat this procedure for each controller that you want to include in the RF group. |
Step 1 | Choose Wireless > 802.11a/n/ac or 802.11b/g/n > RRM > RF Grouping to open the 802.11a (or 802.11b/g) RRM > RF Grouping page. | ||||||||||||
Step 2 | From the
Group Mode drop-down
list, select the mode you want to configure for this Cisco WLC.
You can configure RF grouping in the following modes:
| ||||||||||||
Step 3 | Click Apply to save the configuration and click Restart to restart RRM RF Grouping algorithm. | ||||||||||||
Step 4 | If you
configured RF Grouping mode for this Cisco WLC as a static leader, you can add
group members from the RF Group Members section as follows:
| ||||||||||||
Step 5 | Click Apply. | ||||||||||||
Step 6 | Click Save Configuration. |
Step 1 | Configure the RF Grouping
mode by entering this command:
config advanced {
802.11a |
802.11b}
group-mode {auto |
leader |
off
|
restart}
| ||||||
Step 2 | Add or remove a
Cisco WLC as a static member of the RF group (if the mode is set to “leader”)
by entering the these commands:
| ||||||
Step 3 | See RF grouping status by entering this command: |
This section describes how to view the status of the RF group through either the GUI or the CLI.
Note | You can also view the status of RF groups using the Cisco Prime Infrastructure. |
Step 1 | Choose to open the 802.11a/n/ac (or 802.11b/g/n) RRM > RF Grouping page. This page shows the details of the RF group, displaying the configurable parameter RF Group mode, the RF Group role of this Cisco WLC, the Update Interval and the Cisco WLC name and IP address of the Group Leader to this Cisco WLC.
| ||
Step 2 | (Optional) Repeat this procedure for the network type that you did not select (802.11a/n/ac or 802.11b/g/n). |
Step 1 | See which Cisco WLC is the RF group leader for the 802.11a RF network by entering this command: show advanced 802.11a group Information similar to the following appears: Radio RF Grouping 802.11a Group Mode............................. STATIC 802.11a Group Update Interval.................. 600 seconds 802.11a Group Leader........................... test (209.165.200.225) 802.11a Group Member......................... test (209.165.200.225) 802.11a Last Run............................... 397 seconds ago This output shows the details of the RF group, specifically the grouping mode for the Cisco WLC, how often the group information is updated (600 seconds by default), the IP address of the RF group leader, the IP address of this Cisco WLC, and the last time the group information was updated.
| ||||
Step 2 | See which Cisco WLC is the RF group leader for the 802.11b/g RF network by entering this command: show advanced 802.11b group |
Configuring Rogue Access Point Detection in RF Groups
After you have created an RF group of Cisco WLCs, you need to configure the access points connected to the Cisco WLCs to detect rogue access points. The access points will then select the beacon/probe-response frames in neighboring access point messages to see if they contain an authentication information element (IE) that matches that of the RF group. If the select is successful, the frames are authenticated. Otherwise, the authorized access point reports the neighboring access point as a rogue, records its BSSID in a rogue table, and sends the table to the Cisco WLC.
Configuring Rogue Access Point Detection in RF Groups
Step 1 | Make sure that each Cisco WLC in the RF group has been configured with the same RF group name.
| ||
Step 2 | Choose Wireless to open the All APs page. | ||
Step 3 | Click the name of an access point to open the All APs > Details page. | ||
Step 4 | Choose either local or monitor from the AP Mode drop-down list and click Apply to commit your changes. | ||
Step 5 | Click Save Configuration to save your changes. | ||
Step 6 | Repeat Step 2 through Step 5 for every access point connected to the Cisco WLC. | ||
Step 7 | Choose Security > Wireless Protection Policies > AP Authentication/MFP to open the AP Authentication Policy page. The name of the RF group to which this Cisco WLC belongs appears at the top of the page. | ||
Step 8 | Choose AP Authentication from the Protection Type drop-down list to enable rogue access point detection. | ||
Step 9 | Enter a number in the Alarm Trigger Threshold edit box to specify when a rogue access point alarm is generated. An alarm occurs when the threshold value (which specifies the number of access point frames with an invalid authentication IE) is met or exceeded within the detection period.
| ||
Step 10 | Click Apply to commit your changes. | ||
Step 11 | Click Save Configuration to save your changes. | ||
Step 12 | Repeat this procedure on every Cisco WLC in the RF group.
|
Step 1 | Make sure that each Cisco WLC in the RF group has been configured with the same RF group name.
| ||
Step 2 | Configure a particular access point for local (normal) mode or monitor (listen-only) mode by entering this command: config ap mode local Cisco_AP or config ap mode monitor Cisco_AP | ||
Step 3 | Save your changes by entering this command: save config | ||
Step 4 | Repeat Step 2 and Step 3 for every access point connected to the Cisco WLC. | ||
Step 5 | Enable rogue access point detection by entering this command: config wps ap-authentication | ||
Step 6 | Specify when a rogue access point alarm is generated by entering this command. An alarm occurs when the threshold value (which specifies the number of access point frames with an invalid authentication IE) is met or exceeded within the detection period. config wps ap-authentication threshold
| ||
Step 7 | Save your changes by entering this command: save config | ||
Step 8 | Repeat Step 5 through Step 7 on every Cisco WLC in the RF group.
|
Off-Channel Scanning and Neighbor Discovery
Configuring Off-Channel Scanning Defer
In deployments with certain power-save clients, you sometimes need to defer the Radio Resource Management's (RRM) normal off-channel scanning to avoid missing critical information from low-volume clients (for example, medical devices that use power-save mode and periodically send telemetry information). This feature improves the way that Quality of Service (QoS) interacts with the RRM scan defer feature.
You can use a client's Wi-Fi Multimedia (WMM) UP marking to configure the access point to defer off-channel scanning for a configurable period of time if it receives a packet marked UP.
Off-Channel Scanning Defer is essential to the operation of RRM, which gathers information about alternate channel choices such as noise and interference. Additionally, Off-Channel Scanning Defer is responsible for rogue detection. Devices that need to defer Off-Channel Scanning Defer should use the same WLAN as often as possible. If there are many of these devices (and the possibility exists that Off-Channel Defer scanning could be completely disabled by the use of this feature), you should implement an alternative to local AP Off-Channel Scanning Defer, such as monitoring access points, or other access points in the same location that do not have this WLAN assigned.
You can assign a QoS policy (bronze, silver, gold, and platinum) to a WLAN to affect how packets are marked on the downlink connection from the access point regardless of how they were received on the uplink from the client. UP=1,2 is the lowest priority, and UP=0,3 is the next higher priority. The marking results of each QoS policy are as follows:
Configuring Off-Channel Scanning Defer for WLANs
Step 1 | Choose WLANs to open the WLANs page. |
Step 2 | Click the ID number of the WLAN to which you want to configure off-channel scanning Defer. |
Step 3 | Choose the Advanced tab from the WLANs > Edit page. |
Step 4 | From the Off Channel Scanning Defer section, set the Scan Defer Priority by clicking on the priority argument. |
Step 5 | Set the time in milliseconds in the Scan Defer Time text box. Valid values are 100 through 60000. The default value is 100 milliseconds. |
Step 6 | Click Apply to save your configuration. |
Step 1 | Assign a defer-priority for the channel scan by entering this command: config wlan channel-scan defer-priority priority [enable | disable] WLAN-id The valid range for the priority argument is 0 to 7. The priority is 0 to 7 (this value should be set to 6 on the client and on the WLAN). Use this command to configure the amount of time that scanning will be deferred following an UP packet in the queue. |
Step 2 | Assign the channel scan defer time (in milliseconds) by entering this command: config wlan channel-scan defer-time msec WLAN-id The time value is in miliseconds (ms) and the valid range is 100 (default) to 60000 (60 seconds). This setting should match the requirements of the equipment on your wireless LAN. You can also configure this feature on the Cisco WLC GUI by selecting WLANs, and either edit an existing WLAN or create a new one. |
You can specify the channels that the dynamic channel assignment (DCA) algorithm considers when selecting the channels to be used for RRM scanning by using the Cisco WLC GUI.
Note | This functionality is helpful when you know that the clients do not support certain channels because they are legacy devices or they have certain regulatory restrictions. |
Step 1 | Disable the 802.11a/n/ac or 802.11b/g/n network as follows: | ||||||||||||
Step 2 | Choose Wireless > 802.11a/n/ac or 802.11b/g/n > RRM > DCA to open the Dynamic Channel Assignment (DCA) page. | ||||||||||||
Step 3 | Choose one of the following options from the
Channel Assignment Method drop-down list to specify
the Cisco WLC’s DCA mode:
| ||||||||||||
Step 4 | From the Interval drop-down list, choose one of the
following options to specify how often the DCA algorithm is allowed to run:
10 minutes,
1 hour,
2 hours,
3 hours,
4 hours,
6 hours,
8 hours,
12 hours, or
24 hours. The default
value is 10 minutes.
| ||||||||||||
Step 5 | From the AnchorTime drop-down list, choose a number to specify the time of day when the DCA algorithm is to start. The options are numbers between 0 and 23 (inclusive) representing the hour of the day from 12:00 a.m. to 11:00 p.m. | ||||||||||||
Step 6 | Select the Avoid Foreign AP Interference check box to cause the Cisco WLC’s RRM algorithms to consider 802.11 traffic from foreign access points (those not included in your wireless network) when assigning channels to lightweight access points, or unselect it to disable this feature. For example, RRM may adjust the channel assignment to have access points avoid channels close to foreign access points. The default value is selected. | ||||||||||||
Step 7 | Select the Avoid Cisco AP Load check box to cause the Cisco WLC’s RRM algorithms to consider 802.11 traffic from Cisco lightweight access points in your wireless network when assigning channels, or unselect it to disable this feature. For example, RRM can assign better reuse patterns to access points that carry a heavier traffic load. The default value is unselected. | ||||||||||||
Step 8 | Select the Avoid Non-802.11a (802.11b) Noise check box to cause the Cisco WLC’s RRM algorithms to consider noise (non-802.11 traffic) in the channel when assigning channels to lightweight access points, or unselect it to disable this feature. For example, RRM may have access points avoid channels with significant interference from nonaccess point sources, such as microwave ovens. The default value is selected. | ||||||||||||
Step 9 | Select the Avoid Persistent Non-WiFi Interference check box to enable the Cisco WLC to ignore persistent non-WiFi interference. | ||||||||||||
Step 10 | From the DCA Channel Sensitivity
drop-down list, choose one of the following options to specify how sensitive
the DCA algorithm is to environmental changes such as signal, load, noise, and
interference when determining whether to change channels:
The default value is Medium. The DCA sensitivity thresholds vary by radio band, as noted in the table below. | ||||||||||||
Step 11 | For 802.11a/n/ac networks only,
choose one of the following channel width options to specify the channel
bandwidth supported for all 802.11n radios in the 5-GHz band:
This page also shows the following nonconfigurable channel parameter settings: | ||||||||||||
Step 12 | Select the
Avoid
check for non-DFS channel to enable the Cisco WLC to avoid checks
for non-DFS channels. DCA configuration requires at least one non-DFS channel
in the list. In the EU countries, outdoor deployments do not support non-DFS
channels. Customers based in EU or regions with similar regulations must enable
this option or at least have one non-DFS channel in the DCA list even if the
channel is not supported by the APs.
| ||||||||||||
Step 13 | In the DCA Channel List area, the DCA Channels text box
shows the channels that are currently selected. To choose a channel, select its
check box in the Select column. To exclude a channel, unselect its check box.
The ranges are as follows: 802.11a—36, 40, 44, 48, 52, 56, 60, 64, 100, 104, 108, 112, 116, 132, 136, 140, 149, 153, 157, 161, 165, 190, 196 802.11b/g—1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 The defaults are as follows: 802.11a—36, 40, 44, 48, 52, 56, 60, 64, 100, 104, 108, 112, 116, 132, 136, 140, 149, 153, 157, 161 802.11b/g—1, 6, 11
| ||||||||||||
Step 14 | If you are using Cisco Aironet 1520 series mesh access points in your network, you need to set the 4.9-GHz channels in the 802.11a band on which they are to operate. The 4.9-GHz band is for public safety client access traffic only. To choose a 4.9-GHz channel, select its check box in the Select column. To exclude a channel, unselect its check box.
The ranges are as follows: 802.11a—1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26 | ||||||||||||
Step 15 | Click Apply. | ||||||||||||
Step 16 | Reenable the 802.11 networks as follows: | ||||||||||||
Step 17 | Click
Save Configuration.
|
Step 1 | Choose Wireless > 802.11a/n/ac or 802.11b/g/n > RRM > General to open the 802.11a/n/ac (or 802.11b/g/n) > RRM > General page. | ||||||
Step 2 | Configure profile thresholds
used for alarming as follows:
| ||||||
Step 3 | From the
Channel
List drop-down list, choose one of the following options to specify
the set of channels that the access point uses for RRM scanning:
| ||||||
Step 4 | Configure monitor intervals as follows:
| ||||||
Step 5 | Click Apply. | ||||||
Step 6 | Click
Save Configuration.
|
Configuring RRM Neighbor Discovery Packets
The Cisco Neighbor Discovery Packet (NDP) is the fundamental tool for RRM and other wireless applications that provides information about the neighbor radio information. You can configure the Cisco WLC to encrypt neighbor discovery packets.
This feature enables you to be compliant with the PCI specifications.
An RF group can only be formed between Cisco WLCs that have the same encryption mechanism. That is, an access point associated to a Cisco WLC that is encrypted can not be neighbors with an access point associated to a Cisco WLC that is not encrypted. The two Cisco WLCs and their access points will not recognize each other as neighbors and cannot form an RF group. It is possible to assign two Cisco WLCs in a static RF group configuration that has mismatched encryption settings. In this case, the two Cisco WLCs do not function as a single RF group because the access points belonging to the mismatched Cisco WLCs do not recognize one another as neighbors in the group.
To configure RRM NDP using the Cisco WLC CLI, enter this command:
config advanced 802.11{a|b} monitor ndp-mode {protected | transparent}
This command configures NDP mode. By default, the mode is set to “transparent”. The following options are available:
Channels
Two adjacent access points on the same channel can cause either signal contention or signal collision. In a collision, data is not received by the access point. This functionality can become a problem, for example, when someone reading an e-mail in a café affects the performance of the access point in a neighboring business. Even though these are completely separate networks, someone sending traffic to the café on channel 1 can disrupt communication in an enterprise using the same channel. Controllers can dynamically allocate access point channel assignments to avoid conflict, and increase capacity and performance. Channels are “reused” to avoid wasting scarce RF resources. In other words, channel 1 is allocated to a different access point far from the café, which is more effective than not using channel 1 altogether.
The controller’s Dynamic Channel Assignment (DCA) capabilities are also useful in minimizing adjacent channel interference between access points. For example, two overlapping channels in the 802.11b/g band, such as 1 and 2, cannot both simultaneously use 11/54 Mbps. By effectively reassigning channels, the controller keeps adjacent channels separated.
Note | We recommend that you use only non-overlapping channels (1, 6, 11, and so on). |
The controller examines a variety of real-time RF characteristics to efficiently handle channel assignments as follows:
Access point received energy—The received signal strength measured between each access point and its nearby neighboring access points. Channels are optimized for the highest network capacity.
Noise—Noise can limit signal quality at the client and access point. An increase in noise reduces the effective cell size and degrades user experience. By optimizing channels to avoid noise sources, the controller can optimize coverage while maintaining system capacity. If a channel is unusable due to excessive noise, that channel can be avoided.
802.11 Interference—Interference is any 802.11 traffic that is not part of your wireless LAN, including rogue access points and neighboring wireless networks. Lightweight access points constantly scan all channels looking for sources of interference. If the amount of 802.11 interference exceeds a predefined configurable threshold (the default is 10 percent), the access point sends an alert to the controller. Using the RRM algorithms, the controller may then dynamically rearrange channel assignments to increase system performance in the presence of the interference. Such an adjustment could result in adjacent lightweight access points being on the same channel, but this setup is preferable to having the access points remain on a channel that is unusable due to an interfering foreign access point.
In addition, if other wireless networks are present, the controller shifts the usage of channels to complement the other networks. For example, if one network is on channel 6, an adjacent wireless LAN is assigned to channel 1 or 11. This arrangement increases the capacity of the network by limiting the sharing of frequencies. If a channel has virtually no capacity remaining, the controller may choose to avoid this channel. In huge deployments in which all non-overlapping channels are occupied, the controller does its best, but you must consider RF density when setting expectations.
Load and utilization—When utilization monitoring is enabled, capacity calculations can consider that some access points are deployed in ways that carry more traffic than other access points (for example, a lobby versus an engineering area). The controller can then assign channels to improve the access point with the worst performance reported. The load is taken into account when changing the channel structure to minimize the impact on clients currently in the wireless LAN. This metric keeps track of every access point’s transmitted and received packet counts to determine how busy the access points are. New clients avoid an overloaded access point and associate to a new access point. This parameter is disabled by default.
The controller combines this RF characteristic information with RRM algorithms to make system-wide decisions. Conflicting demands are resolved using soft-decision metrics that guarantee the best choice for minimizing network interference. The end result is optimal channel configuration in a three-dimensional space, where access points on the floor above and below play a major factor in an overall wireless LAN configuration.
Note | Radios using 40MHz channels in the 2.4-GHz band or 80MHz channels are not supported by DCA. |
The RRM startup mode is invoked in the following conditions:
In a single-controller environment, the RRM startup mode is invoked after the controller is upgraded and rebooted.
In a multiple-controller environment, the RRM startup mode is invoked after an RF Group leader is elected.
You can trigger the RRM startup mode from the CLI.
Note | DCA algorithm interval is set to one hour, but DCA algorithm always runs in default interval of 10min, channel allocation happens for every 10min interval for the first 10 cycles, and channel changes as per DCA algorithm for every 10min. After that it goes back to the configured time interval. This is common for both DCA interval and Anchor time since it follows the steady state. |
Note | If DCA/TPC is turned off on the RF-group member, and auto is set on RF-group leader, the channel/TX power on member gets changed as per the algorithm run on the RF-group leader. |
Overriding RRM
In some deployments, it is desirable to statically assign channel and transmit power settings to the access points instead of relying on the RRM algorithms provided by Cisco. Typically, this is true in challenging RF environments and non standard deployments but not the more typical carpeted offices.
Note | If you choose to statically assign channels and power levels to your access points and/or to disable dynamic channel and power assignment, you should still use automatic RF grouping to avoid spurious rogue device events. |
You can disable dynamic channel and power assignment globally for a Cisco WLC, or you can leave dynamic channel and power assignment enabled and statically configure specific access point radios with a channel and power setting. While you can specify a global default transmit power parameter for each network type that applies to all the access point radios on a Cisco WLC, you must set the channel for each access point radio when you disable dynamic channel assignment. You may also want to set the transmit power for each access point instead of leaving the global transmit power in effect.
We recommend that you assign different nonoverlapping channels to access points that are within close proximity to each other. The nonoverlapping channels in the U.S. are 36, 40, 44, 48, 52, 56, 60, 64, 149, 153, 157, and 161 in an 802.11a network and 1, 6, and 11 in an 802.11b/g network.
Statically Assigning Channel and Transmit Power Settings to Access Point Radios
Step 1 | Choose Wireless > Access Points > Radios > 802.11a/n or 802.11b/g/n to open the 802.11a/n/ac (or 802.11b/g/n) Radios page. This page shows all the 802.11a/n/ac or 802.11b/g/n access point radios that are joined to the Cisco WLC and their current settings. The Channel text box shows both the primary and extension channels and uses an asterisk to indicate if they are globally assigned. | ||||
Step 2 | Hover your cursor over the blue drop-down arrow for the access point for which you want to modify the radio configuration and choose Configure. The 802.11a/n/ac (or 802.11b/g/n) Cisco APs > Configure page appears. | ||||
Step 3 | Specify the RF Channel Assignment from the following options: | ||||
Step 4 | Configure the antenna parameters for this radio as follows:
| ||||
Step 5 | In the RF Channel Assignment area, choose Custom for the Assignment Method under RF Channel Assignment and choose a channel from the drop-down list to assign an RF channel to the access point radio. | ||||
Step 6 | In the Tx Power Level Assignment area, choose the Custom assignment method and choose a transmit power level from the drop-down list to assign a transmit power level to the access point radio. The transmit power level is assigned an integer value instead of a value in mW or dBm. The integer corresponds to a power level that varies depending on the regulatory domain in which the access points are deployed. The number of available power levels varies based on the access point model. However, power level 1 is always the maximum power level allowed per country code setting, with each successive power level representing 50% of the previous power level. For example, 1 = maximum power level in a particular regulatory domain, 2 = 50% power, 3 = 25% power, 4 = 12.5% power, and so on.
| ||||
Step 7 | Choose Enable from the Admin Status drop-down list to enable this configuration for the access point. | ||||
Step 8 | Click Apply. | ||||
Step 9 | Have the Cisco WLC send the access point radio admin state immediately to Cisco Prime Infrastructure as follows: | ||||
Step 10 | Click Save Configuration. | ||||
Step 11 | Repeat this procedure for each access point radio for which you want to assign a static channel and power level. |
Step 1 | Disable the radio of a particular access point on the 802.11a/n/ac or 802.11b/g/n network by entering this command: | ||||||||
Step 2 | Configure the channel width for a particular access point by entering this command:
config {802.11a | 802.11b} chan_width Cisco_AP {20 | 40 | 80 | 160}}
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Step 3 | Enable or disable the use of specific antennas for a particular access point by entering this command:
config {802.11a | 802.11b} 11nsupport antenna {tx | rx} Cisco_AP {A | B | C} {enable | disable} where A, B, and C are antenna ports. A is the right antenna port, B is the left antenna port, and C is the center antenna port. For example, to enable transmissions from the antenna in access point AP1’s antenna port C on the 802.11a network, you would enter this command: config 802.11a 11nsupport antenna tx AP1 C enable
| ||||||||
Step 4 | Specify the external antenna gain, which is a measure of an external antenna’s ability to direct or focus radio energy over a region of space entering this command:
config {802.11a | 802.11b} antenna extAntGain antenna_gain Cisco_AP High-gain antennas have a more focused radiation pattern in a specific direction. The antenna gain is measured in 0.5 dBi units, and the default value is 7 times 0.5 dBi, or 3.5 dBi. If you have a high-gain antenna, enter a value that is twice the actual dBi value (see Cisco Aironet Antenna Reference Guide for antenna dBi values). Otherwise, enter 0. For example, if your antenna has a 4.4-dBi gain, multiply the 4.4 dBi by 2 to get 8.8 and then round down to enter only the whole number (8). The Cisco WLC reduces the actual equivalent isotropic radiated power (EIRP) to make sure that the antenna does not violate your country’s regulations. | ||||||||
Step 5 | Configure beamforming for the 5-GHz radios for all APs or a specific by entering this command:
config 802.11a {global | ap ap-name} {enable | disable} | ||||||||
Step 6 | Specify the channel that a particular access point is to use by entering this command:
config {802.11a | 802.11b} channel ap Cisco_AP channel For example, to configure 802.11a channel 36 as the default channel on AP1, enter the config 802.11a channel ap AP1 36 command. The channel you choose is the primary channel (for example, channel 36), which is used for communication by legacy 802.11a radios and 802.11n 20-MHz radios. 802.11n 40-MHz radios use this channel as the primary channel but also use an additional bonded extension channel for faster throughput, if you chose 40 for the channel width.
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Step 7 | Specify the transmit power level that a particular access point is to use by entering this command:
config {802.11a | 802.11b} txPower ap Cisco_AP power_level For example, to set the transmit power for 802.11a AP1 to power level 2, enter the config 802.11a txPower ap AP1 2 command. The transmit power level is assigned an integer value instead of a value in mW or dBm. The integer corresponds to a power level that varies depending on the regulatory domain in which the access points are deployed. The number of available power levels varies based on the access point model. However, power level 1 is always the maximum power level allowed per country code setting, with each successive power level representing 50% of the previous power level. For example, 1 = maximum power level in a particular regulatory domain, 2 = 50% power, 3 = 25% power, 4 = 12.5% power, and so on. In certain cases, Cisco access points support only 7 power levels for certain channels, so that the Cisco Wireless Controller considers the 7th and 8th power levels as the same. If the 8th power level is configured on those channels, the configuration would fail since the controller considers the 7th power level as the lowest acceptable valid power level. These power values are derived based on the regulatory compliance limits and minimum hardware limitation which varies across different Cisco access points. For example, Cisco 3500, 1140, and 1250 series access points allow the configuration of last power levels because those access points report the "per path power" to the controller, whereas all next generation acess points such as Cisco 3700, 3600, 2600, and 1600 series access points report "total power value" to the controller, thereby decreasing the allowed power levels for newer generation products. For example, if the last power level in the 3600E access point has a power value of 4dbm (total power), then it actually means the power value is -2dbm (per path).
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Step 8 | Save your settings by entering this command: save config | ||||||||
Step 9 | Repeat Step 2 through Step 7 for each access point radio for which you want to assign a static channel and power level. | ||||||||
Step 10 | Reenable the access point radio by entering this command: | ||||||||
Step 11 | Have the Cisco WLC send the access point radio admin state immediately to WCS by entering this command: | ||||||||
Step 12 | Save your changes by entering this command: save config | ||||||||
Step 13 | See the configuration of a particular access point by entering this command:
show ap config {802.11a | 802.11b} Cisco_AP Information similar to the following appears: Cisco AP Identifier.............................. 7 Cisco AP Name.................................... AP1 ... Tx Power Num Of Supported Power Levels ............. 8 Tx Power Level 1 .......................... 20 dBm Tx Power Level 2 .......................... 17 dBm Tx Power Level 3 .......................... 14 dBm Tx Power Level 4 .......................... 11 dBm Tx Power Level 5 .......................... 8 dBm Tx Power Level 6 .......................... 5 dBm Tx Power Level 7 .......................... 2 dBm Tx Power Level 8 .......................... -1 dBm Tx Power Configuration .................... CUSTOMIZED Current Tx Power Level .................... 1 Phy OFDM parameters Configuration ............................. CUSTOMIZED Current Channel ........................... 36 Extension Channel ......................... 40 Channel Width.............................. 40 Mhz Allowed Channel List....................... 36,44,52,60,100,108,116,132, ......................................... 149,157 TI Threshold .............................. -50 Antenna Type............................... EXTERNAL_ANTENNA External Antenna Gain (in .5 dBi units).... 7 Diversity.................................. DIVERSITY_ENABLED 802.11n Antennas Tx A....................................... ENABLED B....................................... ENABLED Rx A....................................... DISABLED B....................................... DISABLED C.................................... ENABLED |
Disabling Dynamic Channel and Power Assignment Globally for a Cisco Wireless LAN Controller
Step 1 | Disable the 802.11a or 802.11b/g network by entering this command: | ||
Step 2 | Disable RRM for all 802.11a or 802.11b/g radios and set all channels to the default value by entering this command: | ||
Step 3 | Enable the 802.11a or 802.11b/g network by entering this command: config {802.11a | 802.11b} enable network
| ||
Step 4 | Save your changes by entering this command: save config |
802.11h Parameters
802.11h informs client devices about channel changes and can limit the transmit power of those client devices.
Step 1 | Disable the 802.11 band as follows: |
Step 2 | Choose Wireless > 802.11a/n > DFS (802.11h) to open the 802.11h Global Parameters page. |
Step 3 | In the Power Constraint area, enter the local power constraint. The valid range is between 0 dBm and 30 dBm. |
Step 4 | In the Channel Switch Announcement area, select the Channel Announcement check box if you want the access point to announce when it is switching to a new channel and the new channel number, or unselect this check box to disable the channel announcement. The default value is disabled. |
Step 5 | If you enabled the channel announcement, the Channel Quiet Mode check box appears. Select this check box if you want the access point to stop transmitting on the current channel, or unselect this check box to disable quiet mode. The default value is disabled. |
Step 6 | Click Apply. |
Step 7 | Reenable the 802.11a band as follows: |
Step 8 | Click Save Configuration. |
Step 1 | Disable the 802.11a network by entering this command: |
Step 2 | Enable or disable an access
point to announce when it is switching to a new channel, and the new channel
number by entering this command:
config 802.11h channelswitch {enable {loud | quiet} | disable} Enter either quiet or loud for the enable parameter. When the quiet mode is enabled, all the clients who can enable 802.11h channel switch announcements should stop transmitting packets immediately because the AP detects that the radar and client devices should also quit transmitting to reduce interference. By default, the Channel Switch feature is in disabled state. |
Step 3 | Configure a new channel using the 802.11h channel announcement by entering this command: |
Step 4 | Configure the 802.11h power
constraint value by entering this command:
config 802.11h powerconstraint value Use increments of 3 dB for the value so that the AP goes down one power level at a time. |
Step 5 | Reenable the 802.11a network by entering this command: |
Step 6 | View the status of the
802.11h parameters by entering this command:
Information similar to the following appears: Power Constraint................................. 0 Channel Switch................................... Disabled Channel Switch Mode.............................. 0 |
Transmit Power
The Cisco WLC dynamically controls access point transmit power based on real-time wireless LAN conditions. You can choose between two versions of transmit power control: TPCv1 and TPCv2. With TPCv1, typically, power can be kept low to gain extra capacity and reduce interference. With TPCv2, transmit power is dynamically adjusted with the goal of minimum interference. TPCv2 is suitable for dense networks. In this mode, there could be higher roaming delays and coverage hole incidents.
The Transmit Power Control (TPC) algorithm both increases and decreases an access point’s power in response to changes in the RF environment. In most instances, TPC seeks to lower an access point's power to reduce interference, but in the case of a sudden change in the RF coverage—for example, if an access point fails or becomes disabled—TPC can also increase power on surrounding access points. This feature is different from coverage hole detection, which is primarily concerned with clients. TPC provides enough RF power to achieve desired coverage levels while avoiding channel interference between access points.
These documents provide more information on Transmit Power Control values for the following access points:
Cisco Aironet 3500 Series http://www.cisco.com/c/en/us/support/wireless/aironet-3500-series/products-installation-guides-list.html
Cisco Aironet 3700 Series http://www.cisco.com/c/en/us/support/wireless/aironet-3700-series/products-installation-guides-list.html
Cisco Aironet 700 Series http://www.cisco.com/c/en/us/support/wireless/aironet-700-series/products-installation-guides-list.html
Cisco Aironet 1530 Series http://www.cisco.com/c/en/us/support/wireless/aironet-1530-series/products-installation-guides-list.html
The TPC algorithm balances RF power in many diverse RF environments. However, it is possible that automatic power control will not be able to resolve some scenarios in which an adequate RF design was not possible to implement due to architectural restrictions or site restrictions—for example, when all access points must be mounted in a central hallway, placing the access points close together, but requiring coverage out to the edge of the building.
In these scenarios, you can configure maximum and minimum transmit power limits to override TPC recommendations. The maximum and minimum TPC power settings apply to all access points through RF profiles in a RF network.
To set the Maximum Power Level Assignment and Minimum Power Level Assignment, enter the maximum and minimum transmit power used by RRM in the text boxes in the Tx Power Control page. The range for these parameters is -10 to 30 dBm. The minimum value cannot be greater than the maximum value; the maximum value cannot be less than the minimum value.
If you configure a maximum transmit power, RRM does not allow any access point attached to the controller to exceed this transmit power level (whether the power is set by RRM TPC or by coverage hole detection). For example, if you configure a maximum transmit power of 11 dBm, then no access point would transmit above 11 dBm, unless the access point is configured manually.
Step 1 | Choose Wireless > 802.11a/n/ac or 802.11b/g/n > RRM > TPC to open the 802.11a/n/ac (or 802.11b/g/n) > RRM > Tx Power Control (TPC) page. | ||||||
Step 2 | Choose the Transmit Power Control version from the following options:
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Step 3 | Choose one of the following options from the Power Level Assignment Method drop-down list to specify the Cisco WLC’s dynamic power assignment mode:
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Step 4 | Enter the maximum and minimum power level assignment values in the Maximum Power Level Assignment and Minimum Power Level Assignment text boxes. The range for the Maximum Power Level Assignment is –10 to 30 dBm. The range for the Minimum Power Level Assignment is –10 to 30 dBm. | ||||||
Step 5 | In the Power Threshold text box, enter the cutoff signal level used by RRM when determining whether to reduce an access point’s power. The default value for this parameter is –70 dBm for TPCv1 and –67 dBm for TPCv2, but can be changed when access points are transmitting at higher (or lower) than desired power levels. The range for this parameter is –80 to –50 dBm. Increasing this value (between –65 and –50 dBm) causes the access points to operate at a higher transmit power. Decreasing the value has the opposite effect. In applications with a dense population of access points, it may be useful to decrease the threshold to –80 or –75 dBm to reduce the number of BSSIDs (access points) and beacons seen by the wireless clients. Some wireless clients might have difficulty processing a large number of BSSIDs or a high beacon rate and might exhibit problematic behavior with the default threshold. This page also shows the following nonconfigurable transmit power level parameter settings:
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Step 6 | Click Apply. | ||||||
Step 7 | Click Save Configuration. |
The RRM coverage hole detection algorithm can detect areas of radio coverage in a wireless LAN that are below the level needed for robust radio performance. This feature can alert you to the need for an additional (or relocated) lightweight access point.
If clients on a lightweight access point are detected at threshold levels (RSSI, failed client count, percentage of failed packets, and number of failed packets) lower than those specified in the RRM configuration, the access point sends a “coverage hole” alert to the controller. The alert indicates the existence of an area where clients are continually experiencing poor signal coverage, without having a viable access point to which to roam. The controller discriminates between coverage holes that can and cannot be corrected. For coverage holes that can be corrected, the controller mitigates the coverage hole by increasing the transmit power level for that specific access point. The controller does not mitigate coverage holes caused by clients that are unable to increase their transmit power or are statically set to a power level because increasing their downstream transmit power might increase interference in the network.
Step 1 | Disable the 802.11 network as follows: | ||
Step 2 | Choose Wireless > 802.11a/n/ac or 802.11b/g/n > RRM > Coverage to open the 802.11a/ac (or 802.11b/g/n) > RRM > Coverage page. | ||
Step 3 | Select the Enable Coverage Hole Detection check box to enable coverage hole detection, or unselect it to disable this feature. If you enable coverage hole detection, the Cisco WLC automatically determines, based on data received from the access points, if any access points have clients that are potentially located in areas with poor coverage. The default value is selected. | ||
Step 4 | In the Data RSSI text box, enter the minimum receive signal strength indication (RSSI) value for data packets received by the access point. The value that you enter is used to identify coverage holes (or areas of poor coverage) within your network. If the access point receives a packet in the data queue with an RSSI value below the value that you enter here, a potential coverage hole has been detected. The valid range is –90 to –60 dBm, and the default value is –80 dBm. The access point takes data RSSI measurements every 5 seconds and reports them to the Cisco WLC in 90-second intervals. | ||
Step 5 | In the Voice RSSI text box, enter the minimum receive signal strength indication (RSSI) value for voice packets received by the access point. The value that you enter is used to identify coverage holes within your network. If the access point receives a packet in the voice queue with an RSSI value below the value that you enter here, a potential coverage hole has been detected. The valid range is –90 to –60 dBm, and the default value is –75 dBm. The access point takes voice RSSI measurements every 5 seconds and reports them to the Cisco WLC in 90-second intervals. | ||
Step 6 | In the Min Failed Client Count per AP text box, enter the minimum number of clients on an access point with an RSSI value at or below the data or voice RSSI threshold. The valid range is 1 to 75, and the default value is 3. | ||
Step 7 | In the Coverage Exception Level per AP text box, enter the percentage of clients on an access point that are experiencing a low signal level but cannot roam to another access point. The valid range is 0 to 100%, and the default value is 25%.
| ||
Step 8 | Click Apply. | ||
Step 9 | Reenable the 802.11 network as follows: | ||
Step 10 | Click Save Configuration. |
RF Profiles
Once you create an AP group and apply RF profiles or modify an existing AP group, the new settings are in effect and the following rules become effective:
AP that has a custom power setting applied for AP power is not in global mode configuration, an RF profile has no effect on this AP. For RF profiling to work, all APs must have their channel and power managed by RRM.
Within the AP group, changing the assignment of an RF profile on either band causes the AP to reboot.
Once you assign an RF profile to an AP group, you cannot make changes to that RF profile. You must change the AP group RF profile settings to none in order to change the RF profile and then add it back to the AP group. You can also work around this restriction by disabling the network that will be affected by the changes that you will be making either for 802.11a or 802.11b.
You cannot delete an RF profile that is applied to an AP group.
RF Profiles allows you to tune groups of APs that share a common coverage zone together and selectively change how RRM will operates the APs within that coverage zone.
For example, a university might deploy a high density of APs in an area where a high number of users will congregate or meet. This situation requires that you manipulate both data rates and power to address the cell density while managing the co-channel interference. In adjacent areas, normal coverage is provided and such manipulation would result in a loss of coverage.
Using RF profiles and AP groups allows you to optimize the RF settings for AP groups that operate in different environments or coverage zones. RF profiles are created for the 802.11 radios. RF profiles are applied to all APs that belong to an AP group, where all APs in that group will have the same profile settings.
The RF profile gives you the control over the data rates and power (TPC) values.
Note | The application of an RF profile does not change the AP’s status in RRM. It is still in global configuration mode controlled by RRM. |
High Density Configurations—The following configurations are available to fine tune RF environments in a dense wireless network:
Client limit per WLAN or radio—Maximum number of clients that can communicate with the AP in a high-density environment.
Client trap threshold—Threshold value of the number of clients that associate with an access point, after which an SNMP trap is sent to the controller and Cisco Prime Infrastructure.
Stadium Vision Configurations—You can configure the following parameter:
Newly installed access points (assigned to the 'default-group' AP group by default) are automatically assigned to the Out-of-Box AP group upon associating with the controller, and their radios are administratively disabled. This eliminates any RF instability caused by the new access points.
When Out-of-Box is enabled, default-group APs currently associated with the controller remain in the default group until they reassociate with the controller.
All default-group APs that subsequently associate with the controller (existing APs on the same controller that have dropped and reassociated, or APs from another controller) are placed in the Out-of-Box AP group.
Note | When removing APs from the Out-of-Box AP group for production use, we recommend that you assign the APs to a custom AP group to prevent inadvertently having them revert to the Out-of-Box AP group. |
Special RF profiles are created per 802.11 band. These RF profiles have default settings for all the existing RF parameters and additional new configurations.
Note | When you disable this feature after you enable it, only subscription of new APs to the Out of Box AP group stops. All APs that are subscribed to the Out of Box AP Group remain in this AP group. The network administrators can move such APs to the default group or a custom AP group upon network convergence. |
Probe response—Probe responses to clients that you can enable or disable.
Probe Cycle Count—Probe cycle count for the RF profile. The cycle count sets the number of suppression cycles for a new client.
Cycle Threshold—Time threshold for a new scanning RF Profile band select cycle period. This setting determines the time threshold during which new probe requests from a client come in a new scanning cycle.
Suppression Expire—Expiration time for pruning previously known 802.11b/g clients. After this time elapses, clients become new and are subject to probe response suppression.
Dual Band Expire—Expiration time for pruning previously known dual-band clients. After this time elapses, clients become new and are subject to probe response suppression.
Client RSSI—Minimum RSSI for a client to respond to a probe.
Window—Load balancing sets client association limits by enforcing a client window size. For example, if the window size is defined as 3, assuming fair client distribution across the floor area, then an AP should have no more than 3 clients associated with it than the group average.
Denial—The denial count sets the maximum number of association denials during load balancing.
Coverage Hole Mitigation Configurations—You can configure the following parameters:
Data RSSI—Minimum receive signal strength indication (RSSI) value for data packets received by the access point. The value that you enter is used to identify coverage holes (or areas of poor coverage) within your network.
Voice RSSI—Minimum receive signal strength indication (RSSI) value for voice packets received by the access point.
Coverage Exception—Percentage of clients on an access point that are experiencing a low signal level but cannot roam to another access point. If an access point has more number of such clients than the configured coverage level it triggers a coverage hole event.
Coverage Level—Minimum number of clients on an access point with an RSSI value at or below the data or voice RSSI threshold to trigger a coverage hole exception.
Avoid foreign AP interference—DCA algorithm bases its optimization on multiple sets of inputs, which include detected traffic and interference from foreign 802.11 traffic access points. Each access point periodically measures interference, noise level, foreign interference, and load and maintains a list of neighbor APs. Foreign AP interference is that which is received from 802.11 non-neighbors (i.e., 802.11 APs which are not in the same RF domain – for instance a foreign 802.11 network). This interference is measured using the same mechanism as the noise level.
Due to being out of the reach of the radio resource management module of the current deployment, such APs may be disruptive for RRM and hence the user is able to unselect their contribution to DCA in an RF profile to disable this feature.
Auto switch-over on Radar detection—With the enhancements made in DFS architecture, radar trigger on the serving channel AP will move to a new best channel that is conformed by RRM Dynamic Channel Assignment (DCA) list. The channel width applied to such AP will also follow respective DCA channel width settings configured globally or under RF Profiles (if configured).
Step 1 | Choose to open the RF profiles page. |
Step 2 | To configure the out-of-box status for all RF profiles, select or unselect the Enable Out Of Box check box. |
Step 3 | Click New. |
Step 4 | Enter the RF Profile Name and choose the radio band. |
Step 5 | Click Apply to configure the customizations of power and data rate parameters. |
Step 6 | In the General tab, enter the description for the RF profile in the Description text box. |
Step 7 | In the 802.11 tab, configure the data rates to be applied to the APs of this profile. |
Step 8 | In the
RRM tab, do the following:
|
Step 9 | In the High Density tab, do the following: |
Step 10 | In the
Client
Distribution tab, do the following:
|
Step 11 | Click Apply to commit your changes. |
Step 12 | Click Save Configuration to save your changes. |
Step 1 | To configure the
out-of-box status for all RF profiles, enter this command:
config rf-profile out-of-box {enable | disable} |
Step 2 | To create or
delete an RF profile, enter this command:
config rf-profile {create {802.11a | 802.11b} | delete} profile-name |
Step 3 | To specify a
description for the RF profile, enter this command:
config rf-profile description text profile-name |
Step 4 | To configure the
data rates to be applied to the APs of this profile, enter this command:
config rf-profile data-rates {802.11a | 802.11b} {disabled | mandatory | supported} rate profile-name |
Step 5 | To configure the
maximum and minimum power level assignment, that is the maximum and minimum
power that the APs in this RF profile are allowed to use, enter this command:
config rf-profile {tx-power-max | tx-power-min} power-value profile-name |
Step 6 | To configure a
custom TPC power threshold for either Version1 or Version 2 of TPC, enter this
command:
config rf-profile {tx-power-control-thresh-v1 | tx-power-control-thresh-v2} power-threshold profile-name |
Step 7 | To configure the
coverage hole detection parameters:
|
Step 8 | To configure the
maximum number of clients to be allowed per AP radio, enter this command:
config rf-profile max-clients num-of-clients profile-name |
Step 9 | To configure the
client trap threshold value, enter this command:
config rf-profile client-trap-threshold threshold-value profile-name |
Step 10 | To configure
multicast, enter this command:
config rf-profile multicast data-rate rate profile-name |
Step 11 | To configure
load balancing, enter this command:
config rf-profile load-balancing {window num-of-clients | denial value} profile-name |
Step 12 | To configure
band select:
|
Step 13 | Configure the
802.11n only mode for an access point group base by entering this command:
config rf-profile 11n-client-only {enable | disable} rf-profile-name In the 802.11n only mode, the access point broadcasts support for 802.11n speeds. Only 802.11n clients are allowed to associate with the access point |
Step 14 | To configure
the DCA parameters for an RF profile:
|
Step 1 | Choose to open the AP Groups page. | ||
Step 2 | Click the AP Group Name to open the AP Group > Edit page. | ||
Step 3 | Click the RF Profile tab to configure the RF profile details. You can choose an RF profile for each band (802.11a/802.11b) or you can choose just one or none to apply to this group.
| ||
Step 4 | Click the APs tab and choose the APs to add to the AP group. | ||
Step 5 | Click Add APs to add the selected APs to the AP group. A warning message displays that the AP group will reboot the APs will rejoin the controller.
| ||
Step 6 | Click Apply. The APs are added to the AP Group. |
Use this command to apply RF profiles to AP groups: