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4.4.6 IGMP Proxy Configuration
Multicasting is useful when the same data needs to be sent to more than one hosts. Using
multicasting as opposed to sending the same data to the individual hosts uses less
network bandwidth. The multicast feature also enables you to receive multicast video
stream from multicast servers.
IP hosts use Internet Group Management Protocol (IGMP) to report their multicast group
memberships to neighboring routers. Similarly, multicast routers use IGMP to discover
which of their hosts belong to multicast groups. This device supports IGMP proxy that
handles IGMP messages. When enabled, this device acts as a proxy for a LAN host
making requests to join and leave multicast groups, or a multicast router sending multicast
packets to multicast group on the WAN side.
When a host wishes to join a multicast group, it sends IGMP REPORT message to the
device's IGMP downstream interface. The proxy sets up a multicast route for the interface
and host requesting the video content. It then forwards the Join to the upstream multicast
router. The multicast IP traffic will then be forwarded to the requesting host. On a leave, the
proxy removes the route and then forwards the leave to the upstream multicast router.
The IGMP Proxy page allows you to enable multicast on WAN and LAN interfaces. The
LAN interface is always served as downstream IGMP proxy, and you can configure one of
the available WAN interfaces as the upstream IGMP proxy.
Upstream: The interface that IGMP requests from hosts are sent to the multicast
router.
Downstream: The interface data from the multicast router are sent to hosts in the
multicast group database.
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