Information About RF Groups
An RF group is a logical collection of controllers that coordinate to perform RRM in a globally optimized manner to perform network calculations on a per-radio basis. Separate RF groups exist for 2.4-GHz and 5-GHz networks. Clustering WLCs into a single RF group enables the RRM algorithms to scale beyond the capabilities of a single WLC .
An RF group is created based on the following parameters:
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User-configured RF network name.
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Neighbor discovery performed at the radio level.
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Country list configured on the controller.
RF grouping runs between MCs.
Lightweight access points periodically send out neighbor messages over the air. Access points using the same RF group name validate messages from each other.
When access points on different controllers hear validated neighbor messages at a signal strength of –80 dBm or stronger, the controllers dynamically form an RF neighborhood in auto mode. In static mode, the leader is manually selected and the members are added to the RF Group.
Note |
RF groups and mobility groups are similar, in that, they both define clusters of controllers , but they are different in terms of their use. An RF group facilitates scalable, system-wide dynamic RF management, while a mobility group facilitates scalable, system-wide mobility and controller redundancy. |
RF Group Leader
RF Group Leader can be configured in two ways as follows:
Note |
RF Group Leader is chosen on the basis of the controller with the greatest AP capacity (platform limit.) If multiple controllers have the same capacity, the leader is the one with the highest management IP address. |
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Auto Mode: In this mode, the members of an RF group elect an RF group leader to maintain a primary power and channel scheme for the group. The RF grouping algorithm dynamically chooses the RF group leader and ensures that an RF group leader is always present. Group leader assignments can and do change (for instance, if the current RF group leader becomes inoperable or RF group members experience major changes).
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Static Mode: In this mode, a user selects a controller as an RF group leader manually. In this mode, the leader and the members are manually configured and fixed. If the members are unable to join the RF group, the reason is indicated. The leader tries to establish a connection with a member every minute if the member has not joined in the previous attempt.
The RF group leader analyzes real-time radio data collected by the system, calculates the power and channel assignments, and sends them to each of the controllers in the RF group. The RRM algorithms ensure system-wide stability, and restrain channel and power scheme changes to the appropriate local RF neighborhoods.
Note |
When a controller becomes both leader and member for a specific radio, you get to view the IPv4 and IPv6 address as part of the group leader. When a Controller A becomes a member and Controller B becomes a leader, the Controller A displays either IPv4 or IPv6 address of Controller B using the address it is connected. So, if both leader and member are not the same, you get to view only one IPv4 or IPv6 address as a group leader in the member. |
The RRM algorithms run at a specified updated interval, which is 600 seconds by default. Between update intervals, the RF group leader sends keepalive messages to each of the RF group members and collects real-time RF data.
Note |
Several monitoring intervals are also available. See the Configuring RRM section for details. |
RF Grouping Failure Reason Codes
RF Grouping failure reason codes and their explanations are listed below:
Reason Code |
Description |
---|---|
1 |
Maximum number (20) of controllers are already present in the group. |
2 |
If the following conditions are met:
|
3 |
Group ID do not match. |
4 |
Request does not include source type. |
5 |
Group spilt message to all member while group is being reformed. |
6 |
Auto leader is joining a static leader, during the process deletes all the members. |
9 |
Grouping mode is turned off. |
11 |
Country code does not match. |
12 |
Controller is up in hierarchy compared to sender of join command (static mode). Requestor is up in hierarchy (auto mode). |
13 |
Controller is configured as static leader and receives join request from another static leader. |
14 |
Controller is already a member of static group and receives a join request from another static leader. |
15 |
Controller is a static leader and receives join request from non-static member. |
16 |
Join request is not intended to the controller. Controller name and IP do not match. |
18 |
RF domain do not match. |
19 |
Controller received a Hello packet at incorrect state. |
20 |
Controller has already joined Auto leader, now gets a join request from static leader. |
21 |
Group mode change. Domain name change from CLI. Static member is removed from CLI. |
22 |
Max switch size (350) is reached |
Additional Reference
Radio Resource Management White Paper: https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-3/b_RRM_White_Paper/b_RRM_White_Paper_chapter_011.html
RF Group Name
A controller is configured in an RF group name, which is sent to all the access points joined to the controller and used by the access points as the shared secret for generating the hashed MIC in the neighbor messages. To create an RF group, you configure all of the controllers to be included in the group with the same RF group name.
If there is any possibility that an access point joined to a controller might hear RF transmissions from an access point on a different controller , you should configure the controller with the same RF group name. If RF transmissions between access points can be heard, then system-wide RRM is recommended to avoid 802.11 interference and contention as much as possible.