Web Management Guide-R06

Table Of Contents
Chapter 14
| Multicast Filtering
Layer 3 IGMP (Query used with Multicast Routing)
– 582 –
Router Discovery” on page 556.)
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.
Figure 368: 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 the proxy
devices independent of the multicast routing protocols used by core routers.
IGMP proxy routing uses a tree topology, where the root of the tree is connected to
a complete multicast infrastructure (with the upstream interface connected to the
Internet as shown in the figure above). In such a simple topology, it is sufficient to
send the group membership information learned upstream, and then to forward
multicast packets based upon that information to the downstream hosts. For the
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