Cisco Systems OL-7426-03 quick start About Cisco Wireless LAN Controller Memory

About Cisco 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 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.

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.

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.

5/26/05	Cisco Wireless LAN Controller Memory
OL-7426-03