Igmp Multicast Proxy Application Note; Ip Multicast Introduction - ZyXEL Communications P-2812HNU-51c Support Notes

P-2812HNU-51C Support Notes

IGMP Multicast Proxy Application Note

IP Multicast Introduction

What is the IP Multicast?

Traditionally, the IP packets are transmitted in two ways: unicast or broadcast.
Multicast is a third way to deliver the IP packets to a group of hosts. Host groups are
identified by the class D IP addresses, i.e., those with "1110" as their higher-order
bits. In dotted decimal notation, host group addresses range from 224.0.0.0 to
239.255.255.255. Among them, 224.0.0.1 is assigned to the permanent IP hosts
group, and 224.0.0.2 is assigned to the multicast routers group.
The IGMP (Internet Group Management Protocol) is the protocol used to support
multicast groups. The latest version is version 2 (See RFC2236). The IP hosts use the
IGMP to report their multicast group membership to any immediate-neighbor
multicast routers, so the multicast routers can decide if a multicast packet needs to
be forwarded. At the start-up, the Prestige queries all directly connect networks to
gather group membership.
After that, the CPE updates the information by periodic queries. The device
implementation of IGMP is also compatible with version 1. The multicast setting can
be turned on or off on the Ethernet and remote nodes.
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