What is Cisco DCA and how does it work with RRM.

This episode is sponsored by Metageek

Cisco RRM DCA – Dynamic Channel Assignment

DCA, or Dynamic Channel Assignment, is a core component of Cisco Radio Resource Management (RRM). It runs a critical algorithm which dynamically changes an access points (AP) client serving channel based on multiple parameters, collectively called a Cost Metric. To really get an understanding of Cisco RRM, start with our previous episode on Cisco NDP.

DCA is configured under 802.11a/n/ac (5 GHz) and 802.11b/g/n (2.4 GHz)

Channel Assignment Method

The first thing you will notice is the Channel Assignment Method of Automatic, Freeze, or Off.

Automatic will run the DCA algorithm at the define Interval which is every 10 minutes by default. The anchor point is used to set the time of day the DCA algorithm would start.

For less frequent channel changes, increase the interval.

Keep in mind that clients will be disconnected briefly for a channel change.

Freeze does not run the DCA algorithm unless triggered.

Off disables the use of RRM and its auto-rf capabilities.

Avoid Foreign AP interference

Enabling this option allows RRM to take surrounding neighboring APs that are not part of your network into consideration.

RRM will create a channel plan to help mitigate co-channel interference.

Avoid Cisco AP Load

This option allows RRM to consider the traffic load on an access point to help build a better channel plan.

I don’t believe in enabling this feature because it can be difficult to make a client device associate with a specific AP.

Avoiding non-802.11a|b noise

This RRM option takes interference on the channel into consideration for the channel plan.

The category of interference is anything coming from a non-AP.

Persistent Device Avoidance

Sometimes there is non-Wi-Fi device interference affecting your wireless network. DCA can help mitigate the issue if Avoid Persistent Non-WiFi Interference option is enabled.

RRM will receive information from CleanAir and if the interference is creating a negative impact, RRM can issue a channel change to avoid it.

Viewing persistent devices can be done by viewing the details of an AP from the web interface. At the bottom of the page are all the persistent devices being tracked including the class type, on what channel the interference was heard, what the duty cycle is, RSSI, and when it was last seen.

DCA Channel Sensitivity

DCA has three different modes it could be in:

* Scheduled – DCA algorithm runs at a selected time. Usually to minimize changes to off peak hours.

* Steady State – DCA algorithm running at a specified interval.

* Startup Mode – Used when making changes to the wireless network architecture. It restarts the DCA algorithm and runs for 100 minutes at high sensitivity.

By default, DCA has a medium channel sensitivity at 15 dB for 5 GHz and 10 dB for 2.4 GHz. This is the DCA Sensitivity Threshold.

By changing the channel sensitivity to high, then a cost metric of 5 dB better will recommend a channel change.

DCA Channel List

To have DCA dynamically select a channel, it must be in the Channel List. You can select specific channels for DCA to select from or select them all, including the UNII-2 channels.

Dynamic Bandwidth Selection

RRM has a flexible way to assign bandwidth to APs by analyzing the RF and selecting the best channel width.

By default, DCA uses 20 MHz channels. You can configure Cisco RRM DCA all the way up to 160 MHz channels or select Best to have RRM pick for you.

If an AP doesn’t support 40/80/160 MHz channels it will not be configure...