ZyXEL Communications P-870HN-5xb User Manual page 113

Chapter 6 LAN Setup
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. 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 Device supports both IGMP version 1 (IGMP-v1) and IGMP version 2 (IGMP-
v2). At start up, the Device queries all directly connected networks to gather
group membership. After that, the Device periodically updates this information. IP
multicasting can be enabled/disabled on the Device LAN and/or WAN interfaces in
the web configurator (LAN; WAN). Select None to disable IP multicasting on
these interfaces.
IP Alias
IP alias allows you to partition a physical network into different logical networks
over the same Ethernet interface. The Device supports three logical LAN interfaces
via its single physical Ethernet interface with the Device itself as the gateway for
each LAN network.
When you use IP alias, you can also configure firewall rules to control access
between the LAN's logical networks (subnets).
Note: Make sure that the subnets of the logical networks do not overlap.
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P-870HN-5xb User's Guide