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Cisco IOS Software Configuration Guide for Cisco Aironet Access Points
OL-30644-01
Chapter 6 Configuring Radio Settings
Enabling and Disabling Reliable Multicast to Workgroup Bridges
Beginning in privileged EXEC mode, follow these steps to configure the encapsulation transformation
method:
Enabling and Disabling Reliable Multicast to Workgroup
Bridges
The Reliable multicast messages from the access point to workgroup bridges setting limits reliable
delivery of multicast messages to up to 20 Cisco Aironet Workgroup Bridges that are associated to the
AP. The default setting, disabled, reduces the reliability of multicast delivery but allows more
workgroup bridges to associate to the wireless device.
Access points and bridges normally treat workgroup bridges not as client devices but as infrastructure
devices, like access points or bridges. Treating a workgroup bridge as an infrastructure device means that
the wireless device reliably delivers multicast packets and some broadcast packets, including Address
Resolution Protocol (ARP) packets, to the workgroup bridge.
The AP sends multicast frames to a multicast address, and then again sends the multicast frames to the
workgroup bridge, encapsulated in a unicast frame, that is acknowledged by the workgroup bridge. This
verification mechanism creates wireless overhead, and reduces the throughput on the access point.
The performance cost of reliable multicast delivery—duplication of each multicast packet sent to each
workgroup bridge—limits the number of infrastructure devices, including workgroup bridges, that can
associate to the wireless device. To increase beyond 20 the number of workgroup bridges that can
maintain a radio link to the wireless device, the wireless device must reduce the delivery reliability of
multicast packets to workgroup bridges. With reduced reliability, the wireless device cannot confirm
whether multicast packets reach the intended workgroup bridge, so workgroup bridges at the edge of the
wireless device's coverage area might lose IP connectivity. When you treat workgroup bridges as client
devices, you increase performance but reduce reliability.
Note This feature is best suited for use with stationary workgroup bridges. Mobile workgroup bridges might
encounter spots in the wireless device's coverage area where they do not receive multicast packets and
lose communication with the wireless device even though they are still associated to it.
A Cisco Aironet Workgroup Bridge provides a wireless LAN connection for up to eight
Ethernet-enabled devices.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface dot11radio {0 | 1slot/port} Enter interface configuration mode for the radio interface. The
2.4-GHz radio is radio 0, and the 5-GHz radio is radio 1.
The 802.11n 2.4-GHz radio is radio 0
The 802.11n 5-GHz radio is radio 1.
Step 3
payload-encapsulation
rfc1042 | dot1h
Set the encapsulation transformation method to RFC 1042
(rfc1042, the default setting) or 802.1h (dot1h).
Step 4
end Return to privileged EXEC mode.
Step 5
copy running-config startup-config (Optional) Save your entries in the configuration file.