Cisco Cisco 2000 Series Wireless LAN Controller
9
Release Notes for Cisco Wireless LAN Controllers and Cisco Aironet Lightweight Access Points for Releases 3.2.78.4 and 3.2.78.0
OL-31336-01
Important Notes
Cisco 7920 Wireless IP Phone Support
When using Cisco 7920 Wireless IP phones with wireless LAN controllers, make sure that the phones
and wireless LAN controllers are configured as follows:
and wireless LAN controllers are configured as follows:
•
Aggressive Load Balancing on the wireless LAN controllers must be disabled on a per-wireless
LAN controller basis. Otherwise, the initial roam attempt by the phone may fail, causing a
disruption in the audio path.
LAN 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 Cisco lightweight access points to communicate its channel usage to wireless devices. Because
Cisco lightweight 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 they should associate with another
Cisco lightweight access point. Use the following instructions to enable the QBSS IE:
the Cisco lightweight access points to communicate its channel usage to wireless devices. Because
Cisco lightweight 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 they should associate with another
Cisco lightweight access point. Use the following instructions to enable the QBSS IE:
–
>sh wlan summary
(use this to determine the WLAN ID No. of the WLAN to which you want to add QBSS support)
(use this to determine the WLAN ID No. of the WLAN to which you want to add QBSS support)
–
>config wlan disable [WLAN ID No.]
–
>config wlan 7920-support ap-cac-limit enable [WLAN ID No.]
–
>config wlan enable [WLAN ID No.]
–
>sh wlan [WLAN ID No.]
(use this command to verify that the WLAN is enabled and the field marked “Dot11-Phone
Mode (7920)” is in the ‘compat’ mode)
(use this command to verify that the WLAN is enabled and the field marked “Dot11-Phone
Mode (7920)” is in the ‘compat’ mode)
–
>save config
•
The Dynamic Transmit Power Control (DTPC) information element (IE) must be enabled using the
config 802.11a dtpc enable and config 802.11a commands. The DTPC information element is a
beacon and probe information element that allows the Cisco lightweight access point to broadcast
information on its transmit power. The Cisco Wireless IP Phone 7920 uses this information to
automatically adjust its transmit power to the same level as the Cisco lightweight access point to
which it is associated. In this manner, both devices are transmitting at the same level.
config 802.11a dtpc enable and config 802.11a commands. The DTPC information element is a
beacon and probe information element that allows the Cisco lightweight access point to broadcast
information on its transmit power. The Cisco Wireless IP Phone 7920 uses this information to
automatically adjust its transmit power to the same level as the Cisco lightweight access point to
which it is associated. In this manner, both devices are transmitting at the same level.
•
The 7920 phones and the wireless LAN controllers do not currently use compatible fast roaming
mechanisms. The phone uses CCKM while the wireless LAN controllers use Proactive Key Caching
(PKC). To minimize roaming latency, static WEP is the recommended security mechanism.
mechanisms. The phone uses CCKM while the wireless LAN controllers use Proactive Key Caching
(PKC). To minimize roaming latency, static WEP is the recommended security mechanism.
•
When configuring WEP, there is a difference in nomenclature the wireless LAN controller and the
7920 phone. Configure the wireless LAN controller for 104 bits when using 128-bit WEP for the
7920.
7920 phone. Configure the wireless LAN controller for 104 bits when using 128-bit WEP for the
7920.
The Upgrade Process
When a wireless LAN controller is upgraded, the code on the associated Cisco lightweight access points
is also automatically upgraded. When a Cisco lightweight access point is loading code, each of its lights
blinks in succession.
is also automatically upgraded. When a Cisco lightweight access point is loading code, each of its lights
blinks in succession.
Caution
Do not power down the wireless LAN controller or any Cisco lightweight access point during this
process, or you might corrupt the software image!
process, or you might corrupt the software image!
Upgrading a wireless LAN controller with a large number of Cisco lightweight access points can take as
long as 30 minutes. The Cisco lightweight access points must remain powered and the wireless LAN
controller must not be reset during this time.
long as 30 minutes. The Cisco lightweight access points must remain powered and the wireless LAN
controller must not be reset during this time.