Assisted Roaming

The 802.11k standard allows clients to request neighbor reports containing information about known neighbor access points that are candidates for a service set transition. The use of the 802.11k neighbor list can limit the need for active and passive scanning.

The assisted roaming feature is based on an intelligent and client optimized neighbor list.

Unlike the Cisco Client Extension (CCX) neighbor list, the 802.11k neighbor list is generated dynamically on-demand and is not maintained on the . The 802.11k neighbor list is based on the location of the clients without requiring the mobility services engine (MSE). Two clients on the same but different APs can have different neighbor lists delivered depending on their individual relationship with the surrounding APs.

By default, the neighbor list contains only neighbors in the same band with which the client is associated. However, a switch exists that allows 802.11k to return neighbors in both bands.

Clients send requests for neighbor lists only after associating with the APs that advertize the RRM (Radio Resource Management) capability information element (IE) in the beacon. The neighbor list includes information about BSSID, channel, and operation details of the neighboring radios.

Assembling and Optimizing the Neighbor List

When the receives a request for an 802.11k neighbor list, the following occurs:

The searches the RRM neighbor table for a list of neighbors on the same band as the AP with which the client is currently associated with.
The checks the neighbors according to the RSSI (Received Signal Strength Indication) between the APs, the current location of the present AP, the floor information of the neighboring AP from Cisco Prime Infrastructure, and roaming history information on the to reduce the list of neighbors to six per band. The list is optimized for APs on the same floor.

Assisted Roaming for Non-802.11k Clients

It is also possible to optimize roaming for non-802.11k clients. You can generate a prediction neighbor list for each client without the client requiring to send an 802.11k neighbor list request. When this is enabled on a WLAN, after each successful client association/reassociation, the same neighbor list optimization is applied on the non-802.11k client to generate the neighbor list and store the list in the mobile station software data structure. Clients at different locations have different lists because the client probes are seen with different RSSI values by different neighbors. Because clients usually probe before any association or reassociation, this list is constructed with the most updated probe data and predicts the next AP that the client is likely to roam to.

We discourage clients from roaming to those less desirable neighbors by denying association if the association request to an AP does not match the entries on the stored prediction neighbor list.

Similar to aggressive load balancing, there is a switch to turn on the assisted roaming feature both on a per-WLAN basis and globally. The following options are available:

Denial count—Maximum number of times a client is refused association.
Prediction threshold—Minimum number of entries required in the prediction list for the assisted roaming feature to be activated.

Because both load balancing and assisted roaming are designed to influence the AP that a client associates with, it is not possible to enable both the options at the same time on a WLAN.

This section contains the following subsections:

Restrictions for Assisted Roaming

This feature is supported only on 802.11n capable indoor access points. For a single band configuration, a maximum of 6 neighbors are visible in a neighbor list. For dual band configuration, a maximum of 12 neighbors are visible.
You can configure assisted roaming only using the CLI.

How to Configure Assisted Roaming

Configuring Assisted Roaming (GUI)

Before you begin

Ensure that you have configured an AP Join Profile prior to configuring the primary and backup controllers.

Procedure

Step 1	Choose Configuration > Wireless Advanced > Optimized Roam.
Step 2	On the 5 GHz Band or 2.4 GHz Band page, select the Optimized Roaming Mode check box.
Step 3	In the Optimized Roaming Data Rate Threshold field, enter a value for the threshold data rate of the client. The following data rates are available: 802.11a—6, 9, 12, 18, 24, 36, 48, and 54. 802.11b—1, 2, 5, 6, 9, 11, 12, 18, 24, 36, 48, and 54. Optimized roaming disassociates clients based on the RSSI of the client data packet and data rate. The client is disassociated if the current data rate of the client is lower than the Optimized Roaming Data Rate Threshold.
Step 4	Click Apply.

Configuring Assisted Roaming (CLI)

Procedure

Command or Action Purpose

Step 1

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 2

wireless assisted-roaming floor-bias dBm

Example:

(config)# wireless assisted-roaming floor-bias 20

Configures neighbor floor label bias. The valid range is from 5 to 25 dBm, and the default value is 15 dBm.

Step 3

wlan wlan-id

Example:

(config)# wlan wlan1

Enters the WLAN configuration submode. The wlan-name is the profile name of the configured WLAN.

Step 4

assisted-roaming neighbor-list

Example:

(wlan)# assisted-roaming neighbor-list

Configures an 802.11k neighbor list for a WLAN. By default, assisted roaming is enabled on the neighbor list when you create a WLAN. The no form of the command disables assisted roaming neighbor list.

Step 5

assisted-roaming dual-list

Example:

(wlan)# assisted-roaming dual-list

Configures a dual-band 802.11k dual list for a WLAN. By default, assisted roaming is enabled on the dual list when you create a WLAN. The no form of the command disables assisted roaming dual list.

Step 6

assisted-roaming prediction

Example:

(wlan)# assisted-roaming prediction

Configures assisted roaming prediction list feature for a WLAN. By default, the assisted roaming prediction list is disabled.

Note

A warning message is displayed and load balancing is disabled for the WLAN if load balancing is already enabled for the WLAN.

Step 7

wireless assisted-roaming prediction-minimum count

Example:

# wireless assisted-roaming prediction-minimum

Configures the minimum number of predicted APs required for the prediction list feature to be activated. The default value is 3.

Note

If the number of the AP in the prediction assigned to the client is less than the number that you specify, the assisted roaming feature will not apply on this roam.

Step 8

wireless assisted-roaming denial-maximum count

Example:

# wireless assisted-roaming denial-maximum 8

Configures the maximum number of times a client can be denied association if the association request is sent to an AP does not match any AP on the prediction. The valid range is from 1 to 10, and the default value is 5.

Step 9

end

Example:

Device(config)# end

Returns to privileged EXEC mode. Alternatively, you can also press Ctrl-Z to exit global configuration mode.

Verifying Assisted Roaming

The following command can be used to verify assisted roaming configured on a WLAN:


Command	Description
show wlan id `wlan-id`	Displays the WLAN parameters on the WLAN.

Configuration Examples for Assisted Roaming

This example shows how to configure the neighbor floor label bias:


# configure terminal
(config)# wireless assisted-roaming floor-bias 10
(config)# end
# show wlan id 23

This example shows how to disable neighbor list on a specific WLAN:


# configure terminal
(config)# wlan test1
(config (wlan)# no assisted-roaming neighbor-list
(config)(wlan)# end
# show wlan id 23

This example shows how to configure the prediction list on a specific WLAN:


# configure terminal
(config)# wlan test1
(config)(wlan)# assisted-roaming prediction
(config)(wlan)# end
# show wlan id 23

This example shows how to configure the prediction list based on assisted roaming prediction threshold and maximum denial count on a specific WLAN:


# configure terminal
(config)# wireless assisted-roaming prediction-minimum 4
(config)# wireless assisted-roaming denial-maximum 4
(config)(wlan)# end
# show wlan id 23

Cisco Catalyst 9800 Series Wireless Controller Software Configuration Guide, Cisco IOS XE Gibraltar 16.11.x

Book Title

Chapter Title

Results

Chapter: Assisted Roaming

Assisted Roaming

Assisted Roaming

Assembling and Optimizing the Neighbor List

Assisted Roaming for Non-802.11k Clients

Restrictions for Assisted Roaming

Configuring Assisted Roaming (GUI)

Before you begin

Procedure

Configuring Assisted Roaming (CLI)

Procedure

Example:

Example:

Example:

Example:

Example:

Example:

Example:

Example:

Example:

Verifying Assisted Roaming

Configuration Examples for Assisted Roaming

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