Chapter 10 WAN
NBG6817 User’s Guide
73
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 52
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 NBG6817 supports both IGMP version 1
(
IGMP-v1
) and IGMP version 2 (
IGMP-v2
).
At start up, the NBG6817 queries all directly connected networks to gather group membership.
After that, the NBG6817 periodically updates this information. IP multicasting can be enabled/
disabled on the NBG6817 WAN interface in the Web Configurator (
WAN
). Select
None
to disable IP
multicasting on these interfaces.
Auto-IP Change
When the NBG6817 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 NBG6817 to change its LAN IP
address to 10.0.0.1 automatically. If the NBG6817’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 NBG6817 switches to use 192.168.1.1
as its LAN IP address.
Figure 53
Auto-IP-Change Example
192.168.1.1
192.168.1.23
10.0.0.1
