Network Router User Manual

5/26/05 Cisco Wireless LAN Controller Memory
OL-7426-03
About Cisco Wireless LAN Controller MemoryCisco Wireless LAN Controller Memory
The Cisco Wireless LAN Controller contain two kinds of memory: volatile RAM, which holds the current,
active Cisco Wireless LAN Controller configuration, and NVRAM (non-volatile RAM), which holds the
reboot configuration. When you are configuring the Operating System in a Cisco Wireless LAN
Controller, you are modifying volatile RAM; you must save the configuration from the volatile RAM to
the NVRAM to ensure that the Cisco Wireless LAN Controller reboots in the current configuration.
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
Each Cisco Wireless LAN Controller has a defined number of communication ports for Cisco 1000 Series
lightweight access points. (The number of ports supported is listed in the Cisco 2000 Series Wireless
LAN Controller Model Numbers, Cisco 4100 Series Wireless LAN Controller Model Numbers, and Cisco
4400 Series Wireless LAN Controller Model Numbers sections.) This means that when multiple Cisco
Wireless LAN Controllers with unused Cisco 1000 Series lightweight access point ports are deployed on
the same network, if one Cisco Wireless LAN Controller fails, the dropped Cisco 1000 Series lightweight
access points automatically poll for unused Cisco Wireless LAN Controller ports and associate with
them.
In 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 Management (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 Controller 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.
Note: During installation, Cisco recommends that you connect all Cisco 1000 Series
lightweight access points to a dedicated Cisco Wireless LAN Controller, and configure
each Cisco 1000 Series lightweight access point for final operation. This step config-
ures each Cisco 1000 Series lightweight access point for a Primary, Secondary, and
Tertiary Cisco Wireless LAN Controller, and allows it to store the configured Cisco
WLAN Solution 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 Mobility group. This prevents the Cisco 1000 Series lightweight access points
from spending time sending out blind polling messages, resulting in a faster recovery
period.