ZyXEL Communications CellPipe 7130 RG User Manual page 262

Chapter 21 IGMP
packets passing through it, picks out the group registration information, and
configures multicasting accordingly. IGMP snooping allows the CellPipe 7130 RG to
learn multicast groups without you having to manually configure them.
The CellPipe 7130 RG forwards multicast traffic destined for multicast groups (that
it has learned from IGMP snooping or that you have manually configured) to ports
that are members of that group. The CellPipe 7130 RG discards multicast traffic
destined for multicast groups that it does not know. IGMP snooping generates no
additional network traffic, allowing you to significantly reduce multicast traffic
passing through your device.
IGMP Proxy
To allow better network performance, you can use IGMP proxy instead of a
multicast routing protocol in a simple tree network topology.
Note: Your CellPipe 7130 RG is an IGMP proxy.
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) for one query VLAN
on the CellPipe 7130 RG. A downstream interface is a port that connects to a host
(such as a computer).
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CellPipe 7130 RG User's Guide