Cisco Cisco 2106 Wireless LAN Controller

The multicast queue depth is 512 packets on all controller platforms. However, the following message 
might appear on 2106 controllers: “Rx Multicast Queue is full on Controller.” This message does not 
appear on 4400 series controllers because the 4400 NPU filters ARP packets while all forwarding 
(multicast or otherwise) and multicast replication are done in the software on the 2106.

This message appears when too many multicast messages are sent to the CPU. In controller software 
releases prior to 5.1, multicast, CDP, and ARP packets share the same queue. However, in software 
releases 5.1 and later, these packets are separated into different queues. There are currently no controller 
commands that can be entered to determine if the multicast receive queue is full. When the queue is full, 
some packets are randomly discarded.

Controller software release 4.1.178.0 or later enables you to configure a MAC-filtering IP address for a 
workgroup bridge (WGB) wired client to allow passive WGB wired clients, such as terminal servers or 
printers with static IP addresses, to be added and remain in the controller’s client table while the WGB 
is associated to a controller in the mobility group. This feature, activated by the config macfilter 
ipaddress MAC_address IP_address CLI command, can be used with any passive device that does not 
initiate any traffic but waits for another device to start communication.

This feature allows the controller to learn the IP address of a passive WGB wired client when the WGB 
sends an IAPP message to the controller that contains only the WGB wired client’s MAC address. Upon 
receiving this message from the WGB, the controller checks the local MAC filter list (or the anchor 
controller’s MAC filter list if the WGB has roamed) for the client’s MAC address. If an entry is found 
and it contains an IP address for the client, the controller adds the client to the controller’s client table.

Unlike the existing MAC filtering feature for wireless clients, you are not required to enable MAC 
filtering on the WLAN for WGB wired clients.

WGB wired clients using MAC filtering do not need to obtain an IP address through DHCP to be added 
to the controller’s client table.

For static devices behind the WGB, additional configuration may be needed. If the device does not send 
any packets, the WGB does not learn the MAC address. Therefore, you need to configure a static entry 
in the forwarding table as follows: bridge 1 address xxxx.xxxx.xxxx forward FastEthernet0.

In controller software release 4.1.185.0 or later, CKIP is supported for use only with static WEP. It is not 
supported for use with dynamic WEP. Therefore, a wireless client that is configured to use CKIP with 
dynamic WEP is unable to associate to a wireless LAN that is configured for CKIP. Cisco recommends 
that you use either dynamic WEP without CKIP (which is less secure) or WPA/WPA2 with TKIP or AES 
(which are more secure).