User Manual

Manage Stacking and Redundancy
305
Wireless Controller
Manage a Redundancy Group With N:1 Redundancy
The wireless controller supports N:1 redundancy with failover. Redundancy is implemented
through the use of the Virtual Router Redundancy Protocol (VRRP).
For information about 1:1 redundancy, see Manage Redundancy for a Single Controller on
page 299.
VRRP N:1 Redundancy Concepts
With N:1 redundancy, you can add one redundant controller for up to three controllers, that is,
a redundancy group can consist of four controllers, one of which is a redundant controller.
The controllers that are served by the redundant controller must function in a stack in which
one controller is the master and the other controllers are the slaves. However, in relation to
the redundant controller (also referred to as the secondary controller), both the master and
the slaves function as primary controllers because the redundant controller can take over for
the master or for any of the slaves.
In an N:1 redundancy group with three primary controllers and one redundant controller, you
could consider the redundant controller to consist of three virtual controllers, each of which
maintains a redundancy relationship with a primary controller. Y
ou need a unique VRRP ID
for each relationship.
Each controller in the redundancy group is assigned a unique controller IP address and a
unique local IP address. Local addresses remain constant so that a controller can always be
identified before and after a failover. If a primary controller fails or is disconnected from the
network, an automatic failover to the redundant controller occurs. The redundant controller
then takes ownership of the controller IP address of the primary controller and takes over all
functions of the primary controller
.
After a failover occurs, redundancy no longer exists for the other primary controllers in the
redundancy group.