Neighbor Discovery Protocol Mode on Access Points

NDP mode

Neighbor Discovery Protocol (NDP) modes are wireless protocol configurations in AP that

  • determine whether NDP packets are transmitted on the serving radio’s configured channel (On‑Channel) or using the legacy Off‑Channel method where the serving radio re-tunes to other channels to transmit NDP.

  • allow selection through a controller setting (Auto or Off‑Channel) to match specific deployment requirements.

  • support mixed (brownfield) deployments where APs with and without scanning radios coexist, automatically choosing the appropriate mode for optimal performance.

Feature history

Feature Name

Release

Description

Neighbor Discovery Protocol Mode on Cisco Catalyst 9124AX Outdoor Access Points

Cisco IOS XE 17.5.1

From this release, supported APs can operate on both on-channel and off-channel NDP modes. The feature is configured per slot:

  • ap dot11 {24ghz | 5ghz} rrm ndp-mode {auto | off-channel}

  • ndp-mode {auto | off-channel}

Supported radios

  • Cisco Aironet 3800 Series (Wi‑Fi 5 with scanning radio; 2.4 GHz or 5 GHz only)

  • Cisco Catalyst 9120 Series Access Points

  • Cisco Catalyst 9130 Series Access Points

  • Cisco Catalyst 9124 Series Access Points

  • All Wi‑Fi 6 and newer Catalyst APs

NDP transmission modes

In outdoor deployments — and in all modern Cisco Wi‑Fi 6 and newer APs — NDP packets are transmitted based on the configured Neighbor Discovery Protocol (NDP) mode, which can be set through the controller to suit deployment requirements.

  • On‑Channel– The serving (client-facing) radio remains on its configured channel and continuously streams NDP packets (about every 20 ms) only on that channel. A full‑time scanning radio (implemented through RF ASIC or equivalent) handles all receive operations across all channels.

  • Off‑Channel (Legacy) – Used when a scanning radio is not present. The serving radio periodically re-tunes off its serving channel to transmit NDP packets on other channels, cycling through all regulatory domain channels in about three minutes. This was the standard behavior in older APs before scanning radios became available.

  • Auto Mode – Default setting. The controller automatically selects the transmission method:

    • If all APs have scanning radios: uses On‑Channel mode for optimal performance.

    • If any AP lacks a scanning radio: uses Off‑Channel mode for compatibility.

You can verify which mode is in use with a packet capture on any serving channel:

  • If On‑Channel is in use, NDP packets appears on that channel at approximately 20 ms intervals as a continuous stream.

  • If Off‑Channel is in use, NDP packets appears on each channel only once during a full scan cycle (about every 3 minutes for all channels combined).

Operational guidelines

  • In greenfield Wi‑Fi 6+ deployments, which includes all modern APs, On‑Channel mode provides the best performance and neighbor acquisition times.

  • In brownfield (mixed) environments, Auto setting ensures the correct mode is chosen and maintains compatibility with legacy devices.

  • 6 GHz deployments always operate in On‑Channel mode (no legacy APs exist for this band).


Note
The performance gain by using On‑Channel NDP is 25% more than the performance over legacy AP’s in 5 and 6 GHz. Legacy APs are Cisco APs that do not have a full‑time scanning radio (RF ASIC or equivalent) and do not support 6 GHz.

Configure RRM NDP mode (GUI)

Set the Radio Resource Management (RRM) neighbor discovery mode for APs. This optimizes wireless network performance.

Use this task to select how access points detect neighbors—either automatically or using off-channel scanning—through the GUI.

Before you begin

Confirm that the radio you want to configure (2.4 GHz or 5 GHz) is enabled.

Procedure

Step 1

Choose Configuration > Radio Configurations > RRM.

Step 2

In the Radio Resource Management window, click either the 5 GHz Band or the 2.4 GHz Band tab.

Step 3

In the General tab, under the Noise/Interference/Rogue/CleanAir/SI Monitoring Channels section, click the RRM Neighbor Discovery Mode toggle button to configure a mode.

Step 4

Click Apply.

The RRM neighbor discovery mode is updated for the selected band.

Configure the NDP mode (CLI)

Set the neighbor discovery protocol (NDP) mode for 802.11 radios using CLI.

Specify whether supported APs transmit NDP packets in auto or off-channel mode for 802.11a/b/g/n/ac radios.

Procedure

Step 1

Enter global configuration mode.

Example:

Device# configure terminal

Step 2

Configure the operating mode for 802.11a neighbor discovery using ap dot11 { 24ghz | 5ghz } rrm ndp-mode {auto | off-channel} command.

Example:

For Brownfield (mixed) deployments:
Device(config)# ap dot11 24ghz rrm ndp-mode auto
Device(config)# ap dot11 5ghz rrm ndp-mode auto

Example:

Greenfield (all APs with RF ASIC conventional radios)
Device(config)# ap dot11 24ghz rrm ndp-mode off-channel

You have configured the NDP mode.

Configure the NDP Type (CLI)

Set which type of Neighbor Discovery Protocol (NDP) messages your AP broadcasts on the selected radio band: 2.4 GHz, 5 GHz, or 6 GHz.

Use this procedure to specify whether NDP messages are protected or transparent when configuring Radio Resource Management (RRM) parameters for an AP through the CLI.

Before you begin

  • Determine which radio (2.4 GHz, 5 GHz, or 6 GHz) you intend to configure.

  • Determine if you want your NDP messages to be protected or transparent.

Procedure

Step 1

Enter global configuration mode.

Example:

Device# configure terminal

Step 2

Configure the NDP type for 802.11a (2.4 GHz), 802.11b (5 GHz), or 802.11 (6 GHz) neighbor discovery using the ap dot11 { 24ghz | 5ghz | 6ghz } rrm ndp-type { protected | transparent } command.

Example:

Device(config)# ap dot11 6ghz rrm ndp-type protected

The two types are protected and transparent.

The AP uses the designated NDP type for neighbor discovery on the specified radio band.

Configure NDP mode in the RF profile (GUI)

Enable or modify Neighbor Discovery Protocol (NDP) mode settings for a specific RF profile to optimize wireless network performance.
NDP mode affects how devices discover neighboring APs within a wireless network RF profile. You can set NDP to Auto or Off-Channel as needed.

Procedure

Step 1

Choose Configuration > Tags & Profiles > RF.

Step 2

Click Add.

The Add RF Profile window is displayed.

Step 3

Click the General tab.

Step 4

Click the NDP Mode toggle button to select the NDP mode as AUTO or as OFF-CHANNEL.

Step 5

Click Apply to Device.

The chosen RF profile is updated with the selected NDP mode setting, which is now active in your wireless environment.

Configure NDP mode in the RF profile (CLI)

Set the operating mode for Neighbor Discovery Protocol (NDP) in a specified RF profile using the CLI.

Use this task to configure the NDP operating mode—either auto or off-channel —for a specific RF profile (2.4 GHz, 5 GHz, or 6 GHz) on your wireless device.

Procedure

Step 1

Enter global configuration mode.

Example:

Device# configure terminal

Step 2

Enter the RF profile configuration using the ap dot11 { 24ghz | 5ghz| 6ghz } rf-profile rf-profile-name command.

Example:

Device(config)# ap dot11 24ghz rf-profile rf-profile-name

Step 3

Configure the operating mode for neighbor discovery.

Example:

Device(config-rf-profile)# ndp-mode mode

The RF profile is updated to use the specified NDP mode on the selected radio band.

Monitor radio statistics and NDP using GUI

View and analyze radio statistics, including NDP capability and mode for APs.
Use this task when you need to check and evaluate the wireless radio status and NDP settings for access points in your network environment.

Note

You can verify which NDP transmission mode is in use with a packet capture on the serving channel:

  • If the AP is using On‑Channel mode, NDP frames will appear on the serving channel at approximately 20 ms intervals as a continuous stream.

  • If the AP is using Off‑Channel (legacy) mode, NDP frames will appear on each channel only once during a full scan cycle (about every 3 minutes for all channels combined). In this case, you may not see NDP frames on the serving channel for long periods while the serving radio is tuned elsewhere.

    .

Procedure

Step 1

Choose Monitoring > Wireless > Radio Statistics.

Step 2

Click either 5 GHz Radios, 2.4 GHz Radios, or Dual-Band Radios tab.

The corresponding radio band window displays the list of configured APs.

Step 3

To view the general attributes of an AP, click the corresponding AP to display the General tab. The following information is displayed:

  • AP Name: Displays the assigned identifier for the AP, which is unique within the network. The AP name can be ASCII characters from 32 to 126, excluding leading and trailing spaces.

  • IP Address: Displays the IP address assigned to the AP in dotted-decimal format.

  • AP Mode: Displays the configured AP mode. The supported modes are:

    • Local: It is the default mode, and it offers a basic service set (BSS) on a specific channel. When the AP does not transmit wireless client frame, it scans other channels to measure noise interference, discover rogue devices, and check for matches against Intrusion Detection System (IDS) events.

    • Monitor: An AP in monitor mode does not transmit. It is a dedicated sensor that checks IDS events, detects rogue APs, and determines the position of wireless stations.

    • Sniffer: You can configure an AP as a network sniffer using the controller. This mode captures and forwards all packets on a particular channel to a remote machine running packet analyzer software. These packets contain information on time stamps, signal strength, packet sizes, and so on. Sniffers allow you to monitor and record network activity and detect problems.

    • Bridge: The AP becomes a dedicated point-to-point or point-to-multipoint bridge. Two APs in bridge mode can connect two remote sites. Multiple APs can also form an indoor or outdoor mesh. Note that you cannot connect to the bridge with clients.

    • Clear: Returns the AP back to client-serving mode depending on the remote site tag configuration.

  • MAC Address: Displays the registered MAC address on the controller.

  • Number of Slots : Displays the number of slots supported by the AP.

  • Radio Type: Displays the radio band configured on the controller. By default, both 802.11b/g/n (2.4-GHz) and 802.11a/n/ac (5-GHz) bands are enabled.

  • Slot ID: Displays the slot on which radio is installed.

  • Sub band Type: Displays the configured radio sub-band.

  • NDP Capability: Displays the supported Neighbor Discovery Protocol (NDP) capability.

  • NDP Mode: Displays the configured NDP mode. If the NDP mode that is configured is AUTO, the controller selects ON-Channel as the NDP mode. If the NDP-mode that is configured is OFF-Channel, the controller selects OFF-Channel as the NDP mode.

Verify NDP mode

To verify the NDP mode, run these commands:

Device# show ap rf-profile name test-24g
Description                       : test
RF Profile Name                   : test-24g
Band                              : 2.4 GHz
Transmit Power Threshold v1       : -70 dBm
Min Transmit Power                : -10 dBm
Max Transmit Power                : 30 dBm
.
.
.
NDP mode                          : Auto 
.
.
.

Device# show ap rf-profile name test-5g detail 
Description                       : Test
RF Profile Name                   : test-5g
Band                              : 5 GHz
Transmit Power Threshold v1       : -70 dBm
Min Transmit Power                : -10 dBm
Max Transmit Power                : 30 dBm
.
.
.
NDP mode                          : Off-channel
.
.
.  

Device# show ap name ap-name config dot11 24ghz  
Cisco AP Identifier                             : 3cxx.0exx.36xx
Cisco AP Name                                   : Cisco-9105AXW-AP
Country Code                                    : Multiple Countries: US,MK,J4,IN
Regulatory Domain Allowed by Country            : 802.11bg:-AEJPQU   802.11a:-ABDEIJNPQU
AP Country Code                                 : US  - United States
AP Regulatory Domain                            : -A
MAC Address                                     : 5cxx.0dxx.e0xx
IP Address Configuration                        : DHCP
.
.
.
NDP mode                                        :  Off-channel
.
.
.

Device# show ap name ap-name config dot11 5ghz
Cisco AP Identifier                             : 3cxx.0exx.36xx
Cisco AP Name                                   : Cisco-9105AXW-AP
Country Code                                    : Multiple Countries: US,MK,J4,IN
Regulatory Domain Allowed by Country            : 802.11bg:-AEJPQU   802.11a:-ABDEIJNPQU
AP Country Code                                 : US  - United States
AP Regulatory Domain                            : -B
MAC Address                                     : 5cxx.0dxx.e0xx
IP Address Configuration                        : DHCP
IP Address                                      : Disabled
.
.
.
NDP mode                                        :  On-channel
.
.
.

Device# show ap dot11 24ghz monitor 
Default 802.11b AP monitoring
  802.11b Monitor Mode                 : Enabled
  802.11b Monitor Channels             : Country channels
  802.11b RRM Neighbor Discover Type   : Transparent
  802.11b AP Coverage Interval         : 180 seconds
  802.11b AP Load Interval             : 60 seconds
  802.11b AP Measurement Interval      : 180 seconds
  802.11b AP Reporting Interval        : 180 seconds
  802.11b NDP RSSI Normalization       : Enabled
  802.11b Neighbor Timeout factor      : 20 
  802.11b NDP mode                     : Auto

Device# show ap dot11 5ghz monitor  
Default 802.11a AP monitoring
  802.11a Monitor Mode                 : Enabled
  802.11a Monitor Channels             : Country channels
  802.11a RRM Neighbor Discover Type   : Transparent
  802.11a AP Coverage Interval         : 180 seconds
  802.11a AP Load Interval             : 60 seconds
  802.11a AP Measurement Interval      : 180 seconds
  802.11a AP Reporting Interval        : 180 seconds
  802.11a NDP RSSI Normalization       : Enabled
  802.11a Neighbor Timeout factor      : 20 
  802.11a NDP mode                     : Auto