Using IP Multicast

- What is IP Multicast ?

Traditionally, IP packets are transmitted in two ways - unicast or broadcast. Multicast is a third way to deliver IP packets to a group of hosts. Host groups are identified by 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.

IGMP (Internet Group Management Protocol) is the protocol used to support multicast groups. The latest version is version 2 (see RFC2236). IP hosts use 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 start up, the ZyAIR queries all directly connected networks to gather group membership.

After that, the ZyAIR updates the information by periodic queries. The ZyAIR implementation of IGMP is also compatible with version 1. The multicast setting can be turned on or off on Ethernet and remote nodes.

- IP Multicast Setup

Enable IGMP in ZyAIR's LAN in menu 3.2:

`Menu 3.2 - TCP/IP and DHCP Ethernet Setup DHCP= Server TCP/IP Setup: Client IP Pool: Starting Address= 192.168.1.33 IP Address= 192.168.1.1 Size of Client IP Pool= 32 IP Subnet Mask= 255.255.255.0 First DNS Server= From ISP RIP Direction= Both IP Address= N/A Version= RIP-1 Second DNS Server= From ISP Multicast= IGMP-v2 IP Address= N/A Edit IP Alias= No Third DNS Server= From ISP IP Address= N/A DHCP Server Address= N/A Press ENTER to Confirm or ESC to Cancel:`

Enable IGMP in ZyAIR's remote node in menu 11.3:

`` `Menu 11.3 - Remote Node Network Layer Options IP Address Assignment= Static IP Address= 172.21.10.52 IP Subnet Mask= 255.255.0.0 Gateway IP Addr= 172.21.0.254 Network Address Translation= Full Feature Metric= 1 Private= N/A RIP Direction= Both Version= RIP-1 Multicast= IGMP-v2 Enter here to CONFIRM or ESC to CANCEL:`

Key Settings:

Multicast | IGMP-v1 for IGMP version 1, IGMP-v2 for IGMP version 2.

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