Cisco Systems OL-8335-02 manual Client Roaming, Primary, Secondary, and Tertiary Controllers

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 1-20for 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.

Cisco Wireless LAN Controller Configuration Guide

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