ZyXEL Communications Armor Z1 NBG6816 User Manual page 67

Chapter 10 WAN
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 43 Multicast Example
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 ARMOR Z1 supports both IGMP version
1 (IGMP-v1) and IGMP version 2 (IGMP-v2).
At start up, the ARMOR Z1 queries all directly connected networks to gather group membership.
After that, the ARMOR Z1 periodically updates this information. IP multicasting can be enabled/
disabled on the ARMOR Z1 WAN interface in the Web Configurator (WAN). Select None to disable
IP multicasting on these interfaces.
Auto-IP Change
When the ARMOR Z1 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 ARMOR Z1 to change its LAN
IP address to 10.0.0.1 automatically. If the ARMOR Z1'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 ARMOR Z1 switches to use
192.168.1.1 as its LAN IP address.
Figure 44 Auto-IP-Change Example
192.168.1.23
192.168.1.1
10.0.0.1
ARMOR Z1 User's Guide
67