Cisco Catalyst 9800 Series Wireless Controller Software Configuration Guide, Cisco IOS XE 26.1.x

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Cisco Catalyst 9800 Series Wireless Controller Software Configuration Guide, Cisco IOS XE 26.1.x

Radio resource management

Updated: April 10, 2026

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Introduces radio resource management, covering real-time RF parameter control, AP monitoring, automated optimization, and key functions like radio resource monitoring, power control, dynamic channel assignment, coverage hole detection, and RF grouping to enhance wireless network performance..

A Radio Resource Management (RRM) is a system that

  • consistently manages real-time RF parameters of a wireless network

  • monitors associated APs for traffic load, interference, noise, coverage, and other metrics,

  • performs critical functions like radio resource monitoring, power control transmission, dynamic channel assignment, and coverage hole detection and correction.

Feature history

Table 1. Feature history table for radio resource management

Feature name

Release information

Feature description

Radio resource management

Cisco IOS XE 16.10.1

Radio Resource Management (RRM) is a feature that automates and optimizes the management of radio frequencies in a wireless network. It enables continuous monitoring of access points (APs) for metrics such as traffic load, interference, noise, and coverage.

Functions of radio resource management

  • Radio Resource Monitoring: Ensures optimal allocation of network resources.

  • Power Control Transmission: Adjusts power levels to maintain network performance.

  • Dynamic Channel Assignment: Allocates channels dynamically to reduce interference and optimize network performance.

  • Coverage Hole Detection and Correction: Identifies and rectifies gaps in coverage to ensure consistent connectivity.

  • RF Grouping: Groups RF resources effectively to manage interference and optimize performance.

Radio resource monitors

Radio resource monitor is a system that

  • detects and configures new devices and APs automatically

  • adjusts associated APs for optimal coverage and capacity, and

  • supports noise and interference monitoring.

  • APs scan all the valid channels for the country of operation as well as for channels available in other locations.

  • The APs in local mode go offchannel for a period not greater than 70 ms to monitor these channels for noise and interference.

  • Packets collected during this time are analyzed to detect rogue APs, rogue clients, ad-hoc clients, and interfering APs.

  • In the presence of voice traffic or other critical traffic (in the last 100 ms), APs can defer off-channel measurements. The APs also defer off-channel measurements based on the WLAN scan priority configurations.

  • Each AP spends only 0.2 percent of its time off channel. This activity is distributed across all the APs so that adjacent APs are not scanning at the same time, which could adversely affect wireless LAN performance.

Mobility controller and mobility agent

Radio frequency groups

A radio frequency group is a collection of controllers that

  • coordinate RRM globally

  • support separate networks for 2.4 GHz and 5 GHz networks, and

  • optimize network calculations on a per-radio basis.

Clustering Cisco Catalyst 9800 Series Wireless Controller into a single RF group enables the RRM algorithms to scale beyond the capabilities of a single Cisco Catalyst 9800 Series Wireless Controller.

RF group creation

Create an RF group using these parameters:

  • User-configured RF network name.

  • Neighbor discovery performed at the radio level.

  • Country list configured on the controller.

RF grouping function run between controllers .

Note
RF groups and mobility groups are similar, in that, they both define clusters of controllers , 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 controller redundancy.

RF neighborhood

APs periodically send out neighbor messages over the air. APs using the same RF group name validate messages from each other.

When APs on different controllers hear validated neighbor messages at a signal strength of –80 dBm (or stronger), the controllers 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.

RF group leader

An RF group leader is a designated device that

  • analyzes real-time radio data collected by the system

  • calculates power and channel assignments, and

  • sends them to each controller in the RF group.

The RRM algorithms ensure system-wide stability, and restrain channel and power scheme changes to the appropriate local RF neighborhoods.

RF Group Leader is selected based on the controller with the greatest AP capacity (platform limit). If multiple controllers have the same capacity, the leader is selected based on the Group ID, which is a combination of the management IP address, AP capacity, random number, and so on. The one with the highest Group ID is selected as the leader.

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 primary 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, a user selects a controller 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 minute if the member has not joined in the previous attempt.

Note

  • When a controller becomes both leader and member for a specific radio, you get to view the IPv4 and IPv6 address as part of the group leader.

    When a Controller A becomes a member and Controller B becomes a leader, the Controller A displays either IPv4 or IPv6 address of Controller B using the address it is connected.

    So, if both leader and member are not the same, you get to view only one IPv4 or IPv6 address as a group leader in the member.

Pinning and cascading

If Dynamic Channel Assignment (DCA) needs to use the worst-performing radio as the single criterion for adopting a new channel plan, it can result in pinning or cascading problems.

The main cause of both pinning and cascading is that any potential channel plan changes are controlled by the RF circumstances of the worst-performing radio. The DCA algorithm does not do this; instead, it does the following:

  • 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 that is 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 an 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 the 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.

RF grouping failure reason codes

RF Grouping failure reason codes and their explanations are listed below:

Table 2. RF Grouping Failure Reason Codes

Reason Code

Description

1

Maximum number (20) of controllers are already present in the group.

2

If the following conditions are met:

  • The request is from a similar powered controller and,

    • Controller is the leader for the other band,

      OR

    • Requestor group is larger.

3

Group ID do not match.

4

Request does not include source type.

5

Group spilt message to all member while group is being reformed.

6

Auto leader is joining a static leader, during the process deletes all the members.

9

Grouping mode is turned off.

11

Country code does not match.

12

Controller is up in hierarchy compared to sender of join command (static mode).

Requestor is up in hierarchy (auto mode).

13

Controller is configured as static leader and receives join request from another static leader.

14

Controller is already a member of static group and receives a join request from another static leader.

15

Controller is a static leader and receives join request from non-static member.

16

Join request is not intended to the controller.

Controller name and IP do not match.

18

RF domain do not match.

19

Controller received a Hello packet at incorrect state.

20

Controller has already joined Auto leader, now gets

a join request from static leader.

21

Group mode change.

Domain name change from CLI.

Static member is removed from CLI.

22

Max switch size (350) is reached

Additional Reference

Radio Resource Management White Paper: https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-3/b_RRM_White_Paper/b_RRM_White_Paper_chapter_011.html

RF group name

An RF group name is a user-configured identifier assigned to a group of wireless LAN controllers that

  • is sent to all the access points joined to the controller

  • coordinate to perform Radio Resource Management (RRM) in a globally optimized manner,

  • serves as a shared secret for generating hashed MIC in neighbor messages, and

  • helps in avoiding RF interference and contention by ensuring system-wide RRM.

To create an RF group, you configure all the controllers to be included in the group with the same RF group name. If there is any possibility that an AP joined to a controller might hear RF transmissions from an AP on a different controller , you should configure the controller with the same RF group name.

If RF transmissions between APs can be heard, then system-wide RRM is recommended to avoid 802.11 interference and contention as much as possible.

Rogue AP detection in RF groups

A rogue AP detection in an RF group is a wireless security feature that

  • enables APs in the group to identify unauthorized neighboring APs

  • uses beacon and probe-response frames to check for matching authentication elements, and

  • automatically reports and records unauthorized devices for network monitoring and response.

After you create an RF group of controllers, you must configure connected access points to detect rogue APs. APs analyze neighbor messages for matching authentication elements. If a match is found, the AP authenticates the frame. If the authentication elements do not match, the AP reports the neighboring AP as rogue, logs its BSSID, and sends the log to the controller or embedded controller.

Secure RF groups

Secure RF groups are a wireless LAN controller feature that

  • encrypt radio frequency grouping and RRM message exchanges over a DTLS tunnel

  • authenticate controllers using wireless management trust-point certificates during the DTLS handshake, and

  • require all participating controllers to belong to the same mobility group.

RF profile configuration recommendation

The RF profile configuration recommendations are:

  • Ensure that the country code configuration on both leader and member controllers match.

  • RF grouping formation will not form if:

    • The group leader has IPv4 address and the group member has IPv6 address.

    • The group leader has IPv6 address and the group member has IPv4 address.

  • Configure the IPv4 address on the group leader if RF grouping occurs between leader and member using IPv6 address.

  • We recommend having the same RF profile configurations on the RF group leader and member controllers.

    • Since the RRM algorithms run on the group leader, they refer to the RF profile configurations of the leader controller. For example, additional channels in the member controller's list are not included by the group leader when it assigns a channel to the radio. Similarly, if there is a difference in configuration for DBS channel width between the leader and member controller, the algorithm only refers to the configurations of the group leader.

  • For premises with over 20 controllers, we recommend that you have a common (non-default) RF network name for up to 20 controllers. The rest of the controllers can be mapped under different RF network names.

  • For better network control, set your controller as static leader.

Examples: RF group configuration

These are examples of RF group name configuration. 

Device# configure terminal
Device(config)# wireless rf-network test1
Device(config)# ap dot11 24ghz shutdown
Device(config)# end
Device# show network profile 5
This example demonstrates how to configure rogue AP sdetection within RF groups. 

Device# ap name ap1 mode clear
Device# end
Device# configure terminal
Device(config)# wireless wps ap-authentication
Device(config)# wireless wps ap-authentication threshold 50
Device(config)# end

Transmit power control

A transmit power control is an automation algorithm that:

  • increases and decreases an access point's power dynamically

  • responds to changes in the RF coverage environment, and

  • provides enough RF power to achieve the required coverage levels while avoiding channel interference.

This feature is different from coverage hole detection, which is primarily concerned with clients.

  • TPC provides enough RF power to achieve the required coverage levels while avoiding channel interference between APs. We recommend that you select TPCv1; TPCv2 option is deprecated.

  • With TPCv1, you can select the channel aware mode; we recommend that you select this option for 5 GHz, and leave it unchecked for 2.4 GHz.

Override the TPC algorithm with minimum and maximum transmit power settings

A Transmit Power Control (TPC) minimum and maximum transmit power setting is a wireless network configuration option that

  • defines the allowed range of RF transmit powers for APs

  • overrides the automatic power adjustment recommendations of the TPC algorithm, and

  • applies settings globally to APs through RF profiles.

The TPC (Transmit Power Control) algorithm automatically balances RF power in various environments. Occasionally, site or architectural constraints require manually overriding TPC recommendations. With minimum and maximum power settings, you ensure APs do not exceed or fall below specific transmit powers, regardless of TPC or automatic adjustments or coverage hole detection.

Each AP model and each regulatory domain has its own allowed power levels. The increments vary: Cisco APs use 3 dB increments, but settings can be chosen in 1 dB increments and rounded.

To set the Maximum Power Level Assignment and Minimum Power Level Assignment, enter the maximum and minimum transmit power used by RRM in the fields in the Tx Power Control window. The range for these parameters is from –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, no AP will transmit above 11 dBm unless the AP is configured manually.

Cisco APs support power level changes in 3 dB granularity. TPC Min and Max power settings allow for values in 1 dB increments. The resulting power level will be rounded to the nearest value supported in the allowed powers entry for the AP model and the current serving channel.

Each AP model has its own set of power levels localized for its regulatory country and region. Moreover, the power levels for the same AP model will vary based on the band and channel it is set to. For more information about Allowed Power Level versus Actual Power (in dBm), use the show ap name <name> config slot <0|1|2|3> command. This command displays the specific number of power levels, the allowed range of power levels, and the current power level setting on the AP.

Dynamic channel assignment

A dynamic channel assignment (DCA) is a wireless LAN management technique that

  • automatically evaluates radio frequency (RF) conditions and network utilization

  • dynamically allocates channels among APs to minimize interference and maximize performance, and

  • continuously updates channel assignments based on system-wide RF analytics and policies.

Features of DCA

Features of DCA are:

  • Dynamic channel allocation: DCA dynamically assigns channels to APs to avoid conflicts and interference, improving network capacity and performance. Two adjacent APs on the same channel can cause signal contention or collision. In a collision, data is not received by the AP. For example, reading an e-mail in a café can affect the performance of an AP in a neighboring business.

    Even though these are separate networks, someone sending traffic to the café on channel 1 can disrupt communication in an enterprise using the same channel. Devices can dynamically allocate AP channel assignments to avoid conflict and increase capacity and performance.

  • Channel reuse: Efficiently reuses channels by assigning the same channel to APs that are physically far apart, maximizing scarce RF resources. In other words, channel 1 is allocated to a different AP far from the café, which is more effective than not using channel 1 altogether.

  • Adjacent channel separation: The device’s DCA capabilities are also useful in minimizing adjacent channel interference between APs.

    For example, two overlapping channels in the 802.11b/g band, such as 1 and 2, cannot simultaneously use 11 or 54 Mbps. By effectively reassigning channels, the device keeps adjacent channels separated.

Channel assignments

The device examines a variety of real-time RF characteristics to efficiently handle channel assignments.

  • AP received energy: The received signal strength measured between each AP and its nearby neighboring AP. Channels are optimized to give you the highest network capacity.

  • Noise: Noise can limit signal quality for your devices and APs. Increased noise reduces cell size and degrades user experience. By optimizing channels to avoid noise sources, the device helps you maintain coverage and 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 a part of your wireless LAN, including rogue APs and neighboring wireless networks. Lightweight APs automatically scan all channels to detect interference sources. If the amount of 802.11 interference exceeds a predefined configurable threshold (the default is 10 percent), the AP sends an alert to the device. Using the RRM algorithms, the device may then dynamically rearrange channel assignments to increase system performance in the presence of the interference. Such an adjustment could result in adjacent lightweight APs being on the same channel, but this setup provides better performance than keeping APs on a channel made unusable by interference.

    In addition, if other wireless networks are present, the device 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 device may choose to avoid this channel. In huge deployments in which all nonoverlapping channels are occupied, the device 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 APs are deployed in ways that carry more traffic than other APs, for example, a lobby versus an engineering area. The device can then assign channels to improve the AP that has performed the worst. The load is taken into account when changing the channel structure to minimize the impact on the clients that are currently in the wireless LAN. This metric keeps track of every AP's transmitted and received packet counts to determine how busy the APs are. New clients avoid an overloaded AP and associate to a new AP. This Load and utilization parameter is disabled by default.

The device 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 result is optimal channel configuration across three dimensions. APs located on different floors play an important role in your wireless LAN configuration.

RRM startup mode

The RRM startup mode is invoked under these conditions:

  • In a single- device environment, the RRM startup mode is invoked after the device is upgraded and rebooted.

  • In a multiple- device environment, the RRM startup mode is invoked after an RF Group leader is elected.

  • You can trigger the RRM startup mode using the ap dot11 {24ghz | 5ghz | 6ghz} rrm dca restart command.

The RRM startup mode runs for 100 minutes (ten iterations at ten-minute intervals). The duration of the RRM startup mode is independent of the DCA interval, sensitivity, and network size. The startup mode consists of ten DCA runs with high sensitivity (making channel changes easy and sensitive to the environment) to converge to a steady-state channel plan. DCA continues to run at the specified interval and sensitivity after the startup mode is finished.

Dynamic bandwidth selection

Dynamic bandwidth selection is a wireless network algorithm that

  • maximizes network throughput by dynamically varying the channel width during operation

  • fine-tunes channel assignments by monitoring channel and Base Station Subsystem (BSS) statistics, and

  • adapts to changes in network conditions, such as transitions from 11n to 11ac, and variable client mixes.

During upgrades from 11n to 11ac, dynamic bandwidth selection enables a smooth transition between configurations by adjusting channel widths and orientation (such as choosing between 40 MHz and 80 MHz bandwidths) in response to fast-changing wireless statistics.

Limitations for DCA

DCA limitations include the following items.

  • DCA supports only 20-MHz channels in the 2.4-GHz band.

  • In a Dynamic Frequency Selection (DFS)-enabled AP environment, enable the UNII2 channels option under the DCA channel to allow 100-MHz separation for the dual 5-GHz radios.

  • The calculation methods for interference and channel utilization differ between 9120 (and older) AP models and the newer 916x and 917x AP models. The 9120 and older APs estimate interference and channel utilization using Wi-Fi data packets received from non-neighbor Wi-Fi sources during scanning. In contrast, the 916x and 917x APs use the radio chip vendor’s hardware-level snapshots to determine channel activity, providing improved accuracy over the older models.

  • Use only nonoverlapping channels (1, 6, 11, and others) for reassigning channels to minimize interference.

  • Channel change does not require you to shut down the radio.

  • The DCA algorithm interval is set to one hour. However, the DCA algorithm always runs at the default interval of 10 minutes. Channel allocation occurs at 10-minute intervals for the first 10 cycles, and channel changes occur every 10 minutes as determined by the DCA algorithm. After these cycles, the DCA algorithm returns to the configured interval.

  • Invoking channel update will not result in any immediate changes until the next DCA interval is triggered.

  • If DCA or Transmit Power Control (TPC) is turned off on the RF group member, and automatic settings are enabled on the RF group leader, the channel or transmit power on the member changes according to the algorithm run on the RF group leader.

Coverage hole detection and correction

A coverage hole detection and correction algorithm is a wireless LAN management mechanism that

  • identifies areas with insufficient radio coverage for reliable performance

  • alerts administrators when access points fail to provide adequate coverage, and

  • adjusts AP transmit power to mitigate correctable coverage holes.

If clients on a lightweight AP are detected at threshold levels such as RSSI, failed client count, percentage of failed packets, and number of failed packets that are lower than those specified in the RRM configuration, the AP sends a “coverage hole” alert to the device. The alert indicates that clients cannot connect to a usable AP because of poor signal coverage.

The device discriminates between coverage holes that can and cannot be corrected. For coverage holes that can be corrected, the device mitigates the coverage hole by increasing the transmit power level for that specific AP.

The device does not mitigate coverage holes caused by clients that are unable to increase their transmit power or are statically set to a power level. Increasing downstream transmit power could increase interference in the network.

Cisco AI enhanced RRM

A Cisco AI enhanced RRM is a wireless radio resource management technology that

  • applies artificial intelligence and machine learning to optimize RF environments

  • operates through distributed data collection from Cisco wireless controllers and cloud-based analytics, and

  • automates and adapts RF parameter tuning for Cisco wireless networks.

The RRM runs as a service in a Cisco Catalyst 9800 Series Wireless Controller. The Cisco RRM manages the RF Group (the components making up the RF Network) based on dynamic measurements between every AP and its neighbors stored in a local database for the entire RF Group. At runtime, the RRM draws the last 10 minutes of the collected data, and gently optimizes based on the current network conditions.

The AI Enhanced RRM integrates the power of Artificial Intelligence and Machine Learning to the reliable and trusted Cisco RRM product family algorithms in the Cloud.

Note

The AI enhanced RRM is coordinated through the Cisco Catalyst Center (on-prem appliance) as a service. The current RRM sites are seamlessly transitioned to an intelligent centralized service. AI enhanced RRM along with other Cisco Catalyst Center services brings a host of new features with it.

Cisco AI Enhanced RRM operates as a distributed RRM service. RF telemetry is collected from the Cisco Access Points by the controller, and passed through the Catalyst Center to the Cisco AI Analytics Cloud where the data is stored. The RRM Algorithms run against this telemetry data stored in the cloud. AI analyzes the solutions, and passes any configuration change information back to the Catalyst Center . The Catalyst Center maintains the control connection with the enrolled controller and passes any individual AP configuration changes back to the APs.

Note

The RRM algorithms run in the cloud against the telemetry data available in the cloud.

The following RRM algorithms run in the cloud while the remaining work in the controller:

  • DCA

  • TPC

  • DBS

  • FRA

Cisco AI enhanced RRM supporting releases

The table covers the controller and Cisco Catalyst Center release versions that support Cisco AI Enhanced RRM support:

Table 3. Controller and Cisco Catalyst Center releases supporting Cisco AI enhanced RRM support

Controller release

Cisco Catalyst Center release

Cisco AI enhanced RRM support

Cisco IOS XE Cupertino 17.9.x

  • Cisco Catalyst Center , Release 2.3.2 or Cisco Catalyst Center , Release 2.3.3

  • Cisco Catalyst Center , Release 2.3.4

  • 2.4GHz and 5GHz

  • 2.4GHz, 5GHz, and 6GHz

Cisco IOS XE Cupertino 17.8.x

  • Cisco Catalyst Center , Release 2.3.2 Cisco Catalyst Center , Release 2.3.3

  • Cisco Catalyst Center , Release 2.3.4

2.4GHz and 5GHz

Cisco IOS XE Cupertino 17.7.x

Cisco Catalyst Center , Release 2.3.2 or Cisco Catalyst Center , Release 2.3.3

2.4GHz and 5GHz

If the location of controller, and APs are provisioned previously, assigning a location enrolls the AI Enhanced RRM Services and the profile to be pushed to the controller. Thus, AI Enhanced RRM becomes the RF Group Leader for the subscribed controller.

For more information on the Cisco Catalyst Center, see Cisco Catalyst Center User Guide .

Restrictions

The restrictions for RRM are:

  • The maximum number of APs supported in an RF group depends on the capacity of the controller platform acting as the RF group leader. For platform-specific RF-group limits, refer the C9800 Radio Resource Management Deployment Guide.

  • If an AP tries to join the RF-group that already holds the maximum number of APs it can support, the device rejects the application and throws an error.

  • Disabling all data rates for default rf-profile or custom rf-profile affects the ISSU upgrade and client join process after the software upgrade (ISSU or non-ISSU). To prevent this, you must enable at least one data rate (for example, ap dot11 24 rate RATE_5_5M enable) on the default rf-profile or custom rf-profile . We recommend that you enable the lowest data rate if efficiency is of prime concern.

  • Keywords like secure are not permissible as RF group names.

  • RRM grouping does not occur when an AP operates in a static channel that is not in the DCA channel list. The Neighbor Discovery Protocol (NDP) is sent only on DCA channels; therefore, when a radio operates on a non-DCA channel, it does not receive NDP on the channel.