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Chapter 8 LAN Setup
P-660RU-Tx User’s Guide
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probably adequate for most networks, unless you have an unusual network
topology.
Both RIP-2B and RIP-2M sends the routing data in RIP-2 format; the difference
being that RIP-2B uses subnet broadcasting while RIP-2M uses multicasting.
8.3.6 Multicast
Traditionally, IP packets are transmitted in one of either two ways - Unicast (1
sender - 1 recipient) or Broadcast (1 sender - everybody on the network).
Multicast delivers IP packets to a group of hosts on the network - not everybody
and not just 1.
IGMP (Internet Group Multicast Protocol) is a network-layer protocol used to
establish membership in a Multicast group - it is not used to carry user data. IGMP
version 2 (RFC 2236) is an improvement over version 1 (RFC 1112) but IGMP
version 1 is still in wide use. IGMP version 3 supports source filtering, reporting or
ignoring traffic from specific source address to a particular host on the network. If
you would like to read more detailed information about interoperability between
IGMP version 2 and version 1, please see sections 4 and 5 of RFC 2236. The class
D IP address is used to identify host groups and can be in the range 224.0.0.0 to
239.255.255.255. The address 224.0.0.0 is not assigned to any group and is used
by IP multicast computers. The address 224.0.0.1 is used for query messages and
is assigned to the permanent group of all IP hosts (including gateways). All hosts
must join the 224.0.0.1 group in order to participate in IGMP. The address
224.0.0.2 is assigned to the multicast routers group.
The P-660RU-Tx supports IGMP version 1 (IGMP-v1), IGMP version 2 (IGMP-v2)
and IGMP version 3 (IGMP-v3). At start up, the P-660RU-Tx queries all directly
connected networks to gather group membership. After that, the P-660RU-Tx
periodically updates this information. IP multicasting can be enabled/disabled on
the P-660RU-Tx LAN and/or WAN interfaces in the web configurator (LAN; WAN).
Select None to disable IP multicasting on these interfaces.