ZyXEL Communications P-660H-T Series - Manual (Page 67)

P-660H/HW-T Series User’ Guide
Chapter 4 LAN Setup 66
4.2.3 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 Prestige supports both IGMP version 1 (IGMP-v1) and IGMP version 2 (IGMP-v2). At
start up, the Prestige queries all directly connected networks to gather group membership.
After that, the Prestige periodically updates this information. IP multicasting can be enabled/
disabled on the Prestige LAN and/or WAN interfaces in the web configurator (LAN; WAN).
Select None to disable IP multicasting on these interfaces.
4.2.4 Any IP
Traditionally, you must set the IP addresses and the subnet masks of a computer and the
Prestige to be in the same subnet to allow the computer to access the Internet (through the
Prestige). In cases where your computer is required to use a static IP address in another
network, you may need to manually configure the network settings of the computer every time
you want to access the Internet via the Prestige.
With the Any IP feature and NAT enabled, the Prestige allows a computer to access the
Internet without changing the network settings (such as IP address and subnet mask) of the
computer, when the IP addresses of the computer and the Prestige are not in the same subnet.
Whether a computer is set to use a dynamic or static (fixed) IP address, you can simply
connect the computer to the Prestige and access the Internet.
The following figure depicts a scenario where a computer is set to use a static private IP
address in the corporate environment. In a residential house where a Prestige is installed, you
can still use the computer to access the Internet without changing the network settings, even
when the IP addresses of the computer and the Prestige are not in the same subnet.