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Cisco Wireless LAN Controller Configuration Guide
OL-8335-02
Chapter 1 Overview
Client Roaming
The operator can monitor the master controller using the WCS Web User Interface and watch as access
points associate with the master controller. The operator can then verify access point configuration and
assign a primary, secondary, and tertiary controller to the access point, and reboot the access point so it
reassociates with its primary, secondary, or tertiary controller.
Note Lightweight access points without a primary, secondary, and tertiary controller assigned always search
for a master controller first upon reboot. After adding lightweight access points through the master
controller, assign primary, secondary, and tertiary controllers to each access point. Cisco recommends
that you disable the master setting on all controllers after initial configuration.
Primary, Secondary, and Tertiary Controllers
In multiple-controller networks, lightweight access points can associate with any controller on the same
subnet. To ensure that each access point associates with a particular controller, the operator can assign
primary, secondary, and tertiary controllers to the access point.
When a primed access point is added to a network, it looks for its primary, secondary, and tertiary
controllers first, then a master controller, then the least-loaded controller with available access point
ports. Refer to the “Cisco Wireless LAN Controller Failover Protection” section on page 1-20 for more
information.
Client Roaming
The Cisco Wireless LAN Solution supports seamless client roaming across Cisco 1000 series
lightweight access points managed by the same Cisco Wireless LAN Controller, between Cisco Wireless
LAN Controllers in the same Cisco WLAN Solution Mobility Group on the same subnet, and across
controllers in the same Mobility Group on different subnets.
Same-Subnet (Layer 2) Roaming
Each Cisco Wireless LAN Controller supports same-controller client roaming across access points
managed by the same controller. This roaming is transparent to the client as the session is sustained and
the client continues using the same DHCP-assigned or client-assigned IP Address. The controller
provides DHCP functionality with a relay function. Same-controller roaming is supported in
single-controller deployments and in multiple-controller deployments.
Inter-Controller (Layer 2) Roaming
In multiple-controller deployments, the Cisco Wireless LAN Solution supports client roaming across
access points managed by controllers in the same mobility group and on the same subnet. This roaming
is also transparent to the client, as the session is sustained and a tunnel between controllers allows the
client to continue using the same DHCP- or client-assigned IP Address as long as the session remains
active. Note that the tunnel is torn down and the client must reauthenticate when the client sends a DHCP
Discover with a 0.0.0.0 client IP Address or a 169.254.*.* client auto-IP Address, or when the
operator-set session timeout is exceeded.