Cisco NDP - Neighbor Discovery Protocol

Cisco NDP

Cisco NDP, brief for Neighbor Revelation Convention and Neighbor Revelation Parcels, may be a basic component of Cisco’s auto RF include, Radio Asset Management (RRM). The reason of NDP is to supply over the discuss (OTA) messages between access points (AP). It screens and oversees what each AP sees within the radio recurrence (RF). It’s basically how each AP sees other APs in an RF Bunch or Neighborhood. The conclusion result is genuine RF way misfortune between APs. I see NDP as a way for APs to construct a outline of their areas in connection to each other based on RF engendering and way misfortunes. Each 180 seconds (3 minutes), an AP will send an over the discuss (OTA) message to a multicast address, 01:0B:85:00:00:00, from each channel. NDP messages are sent at the most noteworthy transmit control and at the least information rate supported for the channel being transmitted on. The transmit control and information rate choice isn't configurable by the conclusion client and is difficult coded. Cisco Neighbor Revelation Convention shapes the premise.

Learn more RRM from the white paper.

NDP is used by the following

- RF Grouping Algorithm


- Transmit Power Control (TPC - basis calculation for TPCv2)


- Flexible Radio Architecture (FRA - basis for coverage overlap factor)


- Rogue detection (If AP isn’t sending NDPs or unintelligible NDP then it is a rogue)


- CleanAir (Used for interference reports)


- CMX (For AP RF distance and path loss measurements)

As you can see, NDP is very important for RRM.

Cisco NDP Packet?

Field Name

Description

Radio Identifier

Slot ID for the sending radio

Group ID

IP Address and Priority code of sends WLC

Hash

RF Group name converted to a hash for authentication

IP address

IP of sending AP’s RRM Group Leader

Encrypted ?

Are we using Encrypted NDP?

Version

Version of NDP

APs Channel

Operating channel of the sending radio

Message Channel

Channel the NDP was sent on

Message Power

The power (in dBm) the message was sent at

Antenna

Antenna pattern of the sending radio

When an AP listens and gets an NDP message, it'll approve the message from the transmitting AP to determine if it may be a part of the same RF gather. In case it’s a substantial NDP, the receiving AP will forward the message to the controller together with data such as the gotten channel and RSSI. If the message isn't within the same RF bunch it'll be invalid and the parcel will be dropped. The message is included to a neighbor database. Each radio on each AP can store up to 34 neighbors requested by RSSI, tall to moo.

Configure Cisco NDP

The frequency in which Neighbor Discovery Packets are sent out can be configured from the WLAN controller. By default, it is 180 seconds (3 minutes). It is recommended to keep this at the default.

The Channel Scan Interval is 180 seconds by default. Each channel dwell has to be completed within 180 seconds.

The Neighbor Timeout Factor is by default set to 5. This multiplier is multiplied by the Neighbor Packet Frequency value to come up with the timeout value. So with a default of 180 seconds for the Neighbor Packet Frequency x 5 = 900 seconds. This is the value used to determine when to prune access points from the neighbor list that have timed out.

To find neighbor information using the Web GUI, click on the Monitor heading and on the left side, expand Access Points > Radios > Select radio.

> select Detail.

Use Command Line

Using the CLI, we can view nearby APs from the controller by selecting which AP to get the view from. There are three options to select from.


(Cisco Controller) >show ap auto-rf ?

802.11-abgn Display information for DualBand 802.11a/b/g/n.


802.11a Display information for 802.11a.


802.11b Display information for 802.11b/g.


802.11-abgn is used for APs with FRA.


802.11a displays information from the 5 GHz radio.


802.11b displays information from the 2.4 GHz radio.

Here’s truncated output from AP1 showing three neighboring APs.


(Cisco Controller)> show ap auto-rf 802.11a AP1


View NDP via CLI on AP


Another great debugging command is to view the RM measurements occurring from the access point. NDP packets will be sent out on each channel as you can see in the output below. I’ve truncated the rest of the messages.


AP1#debug capwap rm measurements

RM Neighbor debugging

Another debugging command at the AP level will display NDP packets being received from other APs, including those not in the same RF group.

AP1#debug capwap rm neighbor

Conclusion

We briefly went over the purpose of Cisco NDP, neighbor discovery protocol, and how crucial it is to the RRM algorithms. I showed you where in the WLC GUI you can make changes to the NDP intervals but it is not recommended to change them other than the Neighbor Timeout Factor interval. In addition to capturing the NDP messages over-the-air, we saw how to capture NDP and some other RRM functions using debug commands from the controller and the AP.
https://mobileinfoworld.com/cisco-ndp-neighbor-discovery-protocol/