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P-660R-Tx v2 Series User’s Guide
51 Chapter 5 LAN Setup
5.4.4 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 ZyXEL Device supports both IGMP version 1 (IGMP-v1) and IGMP version 2 (IGMP-
v2). At start up, the ZyXEL Device queries all directly connected networks to gather group
membership. After that, the ZyXEL Device periodically updates this information. IP
multicasting can be enabled/disabled on the ZyXEL Device LAN and/or WAN interfaces in
the web configurator (LAN; WAN ). Select None to disable IP multicasting on these
interfaces.
5.5 Any IP
Traditionally, you must set the IP addresses and the subnet masks of a computer and the
ZyXEL Device to be in the same subnet to allow the computer to access the Internet (through
the ZyXEL Device). 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 ZyXEL Device.
With the Any IP feature and NAT enabled, the ZyXEL Device 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 ZyXEL Device 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 ZyXEL Device 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 ZyXEL Device 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 ZyXEL Device are not in the
same subnet.