Chapter 14 IGMP
VSG1435-B101 Series User’s Guide
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multicast hosts to learn the IP multicast group membership. It checks IGMP
packets passing through it, picks out the group registration information, and
configures multicasting accordingly. IGMP snooping allows the ZyXEL Device to
learn multicast groups without you having to manually configure them.
The ZyXEL Device 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 ZyXEL Device 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 ZyXEL Device 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 ZyXEL Device. A downstream interface is a port that connects to a host
(such as a computer).
