Дыа. Это все из интро лезет:
Multicast in Wireless LAN Controllers (WLCs)
If your network supports packet multicasting, you can configure the multicast method that the controller uses in order to transport the multicast packets over CAPWAP to all or several access points at the same time. The controller performs multicasting in two modes:
Unicast mode - In this mode, the controller unicasts every multicast packet to every AP associated to the controller. This mode is inefficient, but might be required on networks that do not support multicasting.
Multicast mode - In this mode, the controller sends multicast packets to a CAPWAP multicast group. This method reduces overhead on the controller processor and shifts the work of packet replication to your network, which is much more efficient than the unicast method.
When you use different VLAN/Subnet for AP and WLC then Multicast routing is mandatory on the wired side to support forwarding the downlink CAPWAP Multicast packet from WLC to AP.
When you enable multicast mode and the controller receives a multicast packet from the wired LAN, the controller encapsulates the packet using CAPWAP and forwards the packet to the CAPWAP multicast group address. The controller always uses the management interface for sending multicast packets. Access points in the multicast group receive the packet and forward it to all the BSSIDs mapped to the interface on which clients receive multicast traffic. From the access point perspective, the multicast appears to be a broadcast to all SSIDs.
