Cisco Systems OL-11567-02 Heavily Loaded Controller CPU, RADIUS Servers and the Management VLAN

Important Notes

Heavily Loaded Controller CPU

When the controller CPU is heavily loaded (for example, when doing file copies or other tasks), it does not have time to process all of the ACKs that the NPU sends in response to configuration messages. When this happens, the CPU generates error messages. However, the error messages do not impact service or functionality.

RADIUS Servers and the Management VLAN

The RADIUS server can be on any subnet as long as it can be reached by the management VLAN subnet.

The controllers can be managed via the management VLAN subnet from any other subnet that can reach the management VLAN subnet.

Cisco 7920 Wireless IP Phone Support

When using Cisco 7920 Wireless IP Phones with controllers, make sure that the phones and controllers are configured as follows:

•Aggressive load balancing must be disabled on a per-controller basis. Otherwise, the initial roam attempt by the phone may fail, causing a disruption in the audio path.

•The QoS Basis Service Set (QBSS) information element (IE) must be enabled. The QBSS IE enables the access points to communicate their channel usage to wireless devices. Because access points with high channel usage might not be able to handle real-time traffic effectively, the 7920 phone uses the QBSS value to determine if it should associate with another access point. Use the following commands to enable the QBSS IE:

–sh wlan summary

Note Use this command to determine the WLAN ID number of the WLAN to which you want to add QBSS support.

–config wlan disable wlan_id_number

–config wlan 7920-support ap-cac-limit enable wlan_id_number

–config wlan enable wlan_id_number

–sh wlan wlan_id_number

Note Use this command to verify that the WLAN is enabled and the Dot11-Phone Mode (7920) field is configured for compat mode.

–save config

•The Dynamic Transmit Power Control (DTPC) information element (IE) must be enabled using the config 802.11a dtpc enable command. The DTPC IE is a beacon and probe information element that allows the access point to broadcast information on its transmit power. The Cisco 7920 Wireless IP Phone uses this information to automatically adjust its transmit power to the same level as the access point to which it is associated. In this manner, both devices are transmitting at the same level.

Release Notes for Cisco Wireless LAN Controllers and Lightweight Access Points for Release 3.2.171.6

10 OL-11567-02