Igmp Snooping And Proxy Note - ZyXEL Communications MSC1024G Series User Manual

Chapter 10 Multicast Screens
In IGMP proxy, an upstream interface is the port that is closer to the source (or the root of the
multicast tree) and is able to receive multicast traffic. There should only be one upstream
interface (also known as the query port) on the system to limit bandwidth use. A downstream
interface is a port that connects to a host (such as a computer). A query VLAN determines
which ports are downstream interfaces.
The following figure shows a network example where A is the multicast source while
computers 1, 2 and 3 are the receivers. In the figure A is connected to the upstream interface
and 1, 2 and 3 are connected to the downstream interface.
Figure 111 IGMP Proxy Network Example
A
1
The system will not respond to IGMP join and leave messages on the upstream interface. The
system only responds to IGMP query messages on the upstream interface. The system sends
IGMP query messages to the hosts that are members of the query VLAN.
The system only sends an IGMP leave messages via the upstream interface when the last host
leaves a multicast group.
One of the Ethernet ports acts as the upstream interface. By default, the DSL ports are set as
the downstream interfaces.
The switch does not allow a subscriber port to send multicast traffic (except
static multicast traffic) to an uplink port. Only the uplink port can forward
multicast traffic to the subscriber port(s).

10.1.4 IGMP Snooping and Proxy Note

The IES acts as an IGMPv3 client host for an edge IGMPv3 multicast router and as a IGMPv2/
v3 router for IGMPv2/v3 client hosts (subscribers). The IES can recognize IGMPv3 protocol
messages and forward them towards the IGMP multicast router. It does not support full-
featured IGMPv3 functions like source IP address control specified in RFC 3376.
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MSC1000G/1024G/1224G Series User's Guide