CCNA Wireless 640-722 Official Cert Guide

Using Mobility Groups

Cisco controllers can be organized into mobility groups to facilitate intercontroller roaming. Mobility groups become important as a wireless network scales and there are more controllers cooperating to provide coverage over a large area.

If two controllers are configured to belong to the same mobility group, clients can roam quickly between them. Layer 2 and Layer 3 roaming are both supported, along with CCKM, PKC, and 802.11r credential caching. If two controllers are assigned to different mobility groups, clients can still roam between them, but the roam is not very efficient. Credentials are not cached and shared, so clients must go through a full authentication during the roam.

Mobility groups have an implied hierarchy ...