Campus lan and Wireless lan solution Design Guide

Benefits of RRM 
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 wireless 
network.
Band Select 
Most consumer devices being released today operate in one or both of two frequency ranges, or, 
bands
. Dual-
band devices are quite common; however, the bands supported by the devices are not created equally. The 
properties and number of frequencies available for 2.4 GHz and 5 GHz devices differ significantly, with 5 GHz 
having as much as 8 times the available bandwidth as 2.4 GHz. Even so, the 2.4 GHz physical properties allow 
a device to be heard much further (1.5 times as much) than 5 GHz devices operating at the same power level. 
Band Select allows identification of dual-band clients and helps the devices make informed decisions about 
which frequency range and AP to select. The system does this by simply delaying the response to the 2.4 GHz 
probes from a client and by immediately answering the client when the client uses 5 GHz probes. This system 
behavior encourages clients to use the available superior bandwidth in 5 GHz and increases the overall network 
capacity. 
Organizations are advised to enable Band Select in all environments. For more information on configuring Band 
Select, visit cisco.com and 
search for Wireless Controller Configuration 802.11 Bands
. 
Dynamic bandwidth selection (DBS) 
With the introduction of 802.11n, 802.11ac Wave 1 and Wave 2, and 802.11ax, you can use multiple channels 
together as a single assignment on a given AP. This increases the amount of bandwidth available for a given 
channel and improves the throughput and apparent speed perceived by the client. However, to use these 
combined channels, an AP and a client must both support the capability. 
Bonding channels—using multiple single channels to create a single super channel—has the advantage of 
providing more usable throughput to a client with the capability to use the channel. However, in grouping 
multiple channels to create a single channel, larger slices of the spectrum are consumed, decreasing the overall 

---

© 2020 Cisco and/or its affiliates. All rights reserved. 
Page 61 of 76
number of non-interfering channels to use with DCA. This can result in aggressive channel reuse if there are 
enough APs (each one requires an operating channel) and increased co-channel interference, counter to the 
intended goal of throughput efficiency. 
Dynamic Bandwidth Selection works with the DCA algorithm to monitor the APs and the client types and 
capabilities using the APs. Based on this analysis, DBS assigns appropriate channel widths to APs to 
dynamically balance the bandwidth selection for the types of clients and traffic that each AP uses. 
DBS allows appropriately sized bandwidth to be used for the clients being served, avoids wasting multiple 
channels for devices that likely could not use the added capacity, and avoids the associated interference 
created by those devices. For these reasons, you should run DCA in DBS mode. 
For additional details, visit cisco.com and 
search for High Density Experience (HDX) Deployment Guide
.