Web Management Guide

Chapter 13 | Multicast Filtering
Layer 3 IGMP (Query used with Multicast Routing)
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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 602).
2. Enable IGMP on the downstream interfaces which require proxy multicast
service (see “Configuring IGMP Interface Parameters” on page 474).
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.
Command Usage
◆ 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.
◆ The system periodically checks the multicast route table for (*,G) any-source
multicast forwarding entries. When changes occur in the downstream IGMP
groups, an IGMP state change report is created and sent to the upstream router.
◆ If there is an IGMPv1 or IGMPv2 querier on the upstream network, then the
proxy device will act as an IGMPv1 or IGMPv2 host on the upstream interface