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Information About Multicast Optimization
Multicast used to be based on the group of the multicast addresses and the VLAN as one entity, MGID. With
the VLAN group, duplicate packets might increase. Using the VLAN group feature, every client listens to
the multicast stream on a different VLAN. As a result, the device creates different MGIDs for each multicast
address and VLAN. Therefore, in a worst case situation, the upstream router sends one copy for each VLAN,
which results in as many copies as the number of VLANs in the group. Because the WLAN remains the same
for all clients, multiple copies of the multicast packet are sent over the wireless network. To suppress the
duplication of a multicast stream on the wireless medium between the device and the access points, the
multicast optimization feature can be used.
Multicast optimization enables you to create a multicast VLAN that can be used for multicast traffic. One of
the VLANs in the device can be configured as a multicast VLAN where multicast groups are registered. The
clients are allowed to listen to a multicast stream on the multicast VLAN. The MGID is generated using the
mulicast VLAN and multicast IP addresses. If multiple clients on different VLANs of the same WLAN are
listening to a single multicast IP address, a single MGID is generated. The device makes sure that all multicast
streams from the clients on this VLAN group always go out on the multicast VLAN to ensure that the upstream
router has one entry for all the VLANs of the VLAN group. Only one multicast stream hits the VLAN group
even if the clients are on different VLANs. Therefore, the multicast packets that are sent out over the network
is just one stream.
Related Topics
Configuring IP Multicast VLAN for WLAN (CLI), on page 225
How to Configure Wireless Multicast
Configuring Wireless Multicast-MCMC Mode (CLI)
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
wireless multicast
4.
ap capwap multicast ipaddr
5.
end
DETAILED STEPS
Purpose
Command or Action
Enables privileged EXEC mode.
enable
Step 1
Example:
Device>
enable
•
Enter your password if prompted.
IP Multicast Routing Configuration Guide, Cisco IOS XE Release 3SE (Catalyst 3650 Switches)
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Configuring Wireless Multicast
Information About Multicast Optimization