User's Manual

Table Of Contents
3/11/05 Cisco Wireless LAN Controller Failover Protection
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Knowing which memory you are modifying is important when you are:
Using the Startup Wizard
Clearing Configurations
Saving Configurations
Resetting the Cisco Wireless LAN Controller
Logging Out of the CLI
Cisco Wireless LAN Controller Failover ProtectionCisco Wireless LAN Controller Failover Protection
The Cisco 2000 Series Wireless LAN Controller can associate with up to six Cisco 1000 Series light-
weight access points. The Cisco 4100 Series Wireless LAN Controller can associate with up to 36 Cisco
1000 Series lightweight access points.
In a multiple-Cisco Wireless LAN Controller Cisco SWAN (refer to Multiple-Cisco Wireless LAN Controller
Deployments), this means that if one Cisco Wireless LAN Controller fails, its dropped Cisco 1000 Series
lightweight access points reboot and do the following under direction of the Radio Resource Manage-
ment (RRM):
Obtain an IP address from a local DHCP server (one on the local subnet).
If the Cisco 1000 Series lightweight access point has a Primary, Secondary, and Tertiary Cisco
Wireless LAN Controllers assigned, it attempts to associate with that Cisco Wireless LAN
Controller.
If the Cisco 1000 Series lightweight access point has no Primary, Secondary, or Tertiary Cisco
Wireless LAN Controllers assigned or if its Primary, Secondary, and Tertiary Cisco Wireless LAN
Controllers are unavailable, it attempts to associate with a Master Cisco Wireless LAN Controller
on the same subnet.
If the Cisco 1000 Series lightweight access point finds no Master Cisco Wireless LAN Controller
on the same subnet, it attempts to contact stored Controller Mobility Group members by IP
address.
Should none of the Controller Mobility Group members be available, and if the Cisco 1000
Series lightweight access point has no Primary, Secondary, and Tertiary Cisco Wireless LAN
Controllers assigned and there is no Master Cisco Wireless LAN Controller active, it attempts to
associate with the least-loaded Cisco Wireless LAN Controllers on the same subnet to respond
to its discovery messages with unused ports.
This means that when sufficient Cisco Wireless LAN Controllers are deployed in Appliance Mode
, should
one Cisco Wireless LAN Controller fail, active Cisco 1000 Series lightweight access point client sessions
Note: During installation, Cisco recommends that you connect all Cisco 1000 Series
lightweight access points to a configured Cisco Wireless LAN Controller, and
configure each Cisco 1000 Series lightweight access point for final operation. This
step configures each Cisco 1000 Series lightweight access point for Primary,
Secondary, and Tertiary Cisco Wireless LAN Controllers, and allows it to store the
configured Controller Mobility Group information.
During failover recovery, the configured Cisco 1000 Series lightweight access points
obtain an IP address from the local DHCP server (only in Layer 3 Operation), attempt
to contact their Primary, Secondary, and Tertiary Cisco Wireless LAN Controllers, and
then attempt to contact the IP addresses of the other Cisco Wireless LAN Controllers
in the Controller Mobility Group. This will prevent the Cisco 1000 Series lightweight
access points from spending time sending out blind polling messages, resulting in a
faster recovery period.