User Manual

C HAPTER 15 | Multicast Filtering
Layer 3 IGMP (Query used with Multicast Routing)
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N OTE : Multicast Routing Discovery (MRD) is used to discover which
interfaces are attached to multicast routers. (For a description of this
protocol, see “Multicast Router Discovery” on page 522.)
IGMP Proxy – A device can learn about the multicast service requirements
of hosts attached to its downstream interfaces, proxy this group
membership information to the upstream router, and forward multicast
packets based on that information.
CONFIGURING IGMP
PROXY ROUTING
Use the Multicast > IGMP > Proxy page to configure IGMP Proxy Routing.
In simple network topologies, it is sufficient for a device to learn multicast
requirements from its downstream interfaces and proxy this group
membership information to the upstream router. Multicast packets can
then be forwarded downstream based solely upon that information. This
mechanism, known as IGMP proxy routing, enables the system to issue
IGMP host messages on behalf of hosts that the system has discovered
through standard IGMP interfaces.
CLI REFERENCES
◆ "IGMP Proxy Routing" on page 1270
Figure 319: IGMP Proxy Routing
Using IGMP proxy routing to forward multicast traffic on edge switches
greatly reduces the processing load on those devices by not having to run
more complicated multicast routing protocols such as PIM. It also makes
Layer3 Switch/Router
Router
PC PC
192.168.1.2
192.168.1.3
192.168.2.1 192.168.3.1 192.168.4.1
PC
PC
PC
Upstream
Interface
IP IGMPProxy
To Internet
Downstream
Interfaces