LevelOne GTL-2691 - Manual (Page 548)

C HAPTER 15 | Multicast Filtering
Layer 3 IGMP (Query used with Multicast Routing)
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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 switch,
IGMP proxy routing has only one upstream connection to the core network
side and multiple downstream connections to the customer side.
The IGMP proxy routing tree must be manually configured by designating
one upstream interface and multiple downstream interfaces on each proxy
device. No other multicast routers except for the proxy devices can exist
within the tree, and the root of the tree must be connected to a wider
multicast infrastructure. Note that this protocol is limited to a single
administrative domain.
In more complicated scenarios where the topology is not a tree (such as
when there are diverse paths to multiple sources), a more robust failover
mechanism should be used. If more than one administrative domain is
involved, a multicast routing protocol should be used instead of IGMP
proxy.
To enable IGMP proxy service, follow these steps:
1.
Enable IP multicasting globally on the router (see "Configuring Global
Settings for Multicast Routing" on page 708 ).
2. Enable IGMP on the downstream interfaces which require proxy
multicast service (see
"Configuring IGMP Interface Parameters" on
page 550 ).
3.
Enable IGMP proxy on the interface that is attached to an upstream
multicast router using the proxy settings described in this section.
4. Optional – Indicate how often the system will send unsolicited reports
to the upstream router using the Multicast > IGMP > Proxy page as
described later in this section.
C OMMAND U SAGE
◆ When IGMP proxy is enabled on an interface, that interface is known as
the upstream or host interface. This interface performs only the host
portion of IGMP by sending IGMP membership reports, and
automatically disables IGMP router functions.
◆ Interfaces with IGMP enabled, but not located in the direction of the
multicast tree root are known as downstream or router interfaces.
These interfaces perform the standard IGMP router functions by
maintaining a database of all IGMP subscriptions on the downstream
interface. IGMP must therefore be enabled on all interfaces which
require proxy multicast service.