ZyXEL Communications NBG6604 User Manual page 52

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.
Figure 28 Multicast Example
A
B
C
D
In the multicast example above, systems A and D comprise one multicast group. In multicasting, the
server only needs to send one data stream and this is delivered to systems A and D.
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. The NBG6604 supports both IGMP version 1 (IGMP-v1)
and IGMP version 2 (IGMP-v2).
At start up, the NBG6604 queries all directly connected networks to gather group membership. After
that, the NBG6604 periodically updates this information. IP multicasting can be enabled/disabled on the
NBG6604 WAN interface in the Web Configurator (WAN). Select None to disable IP multicasting on these
interfaces.
Auto-IP Change
When the NBG6604 gets a WAN IP address or a DNS server IP address which is in the same subnet as the
LAN IP address 192.168.1.1, Auto-IP-Change allows the NBG6604 to change its LAN IP address to 10.0.0.1
automatically. If the NBG6604's original LAN IP address is 10.0.0.1 and the WAN IP address is in the same
subnet, such as 10.0.0.3, the NBG6604 switches to use 192.168.1.1 as its LAN IP address.
Chapter 9 WAN
Server
NBG6604 User's Guide
52