User's Manual

Chapter 13 WAN
NBG6515 User’s Guide
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13.3.2 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 78 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 NBG supports both IGMP version 1
(IGMP-v1) and IGMP version 2 (IGMP-v2).
At start up, the NBG queries all directly connected networks to gather group membership. After
that, the NBG periodically updates this information. IP multicasting can be enabled/disabled on the
NBG LAN and/or WAN interfaces in the Web Configurator (LAN; WAN). Select None to disable IP
multicasting on these interfaces.
13.4 Internet Connection
Use this screen to change your NBG’s Internet access settings. Click WAN from the Configuration
menu. The screen differs according to the encapsulation you choose.
13.4.1 Ethernet Encapsulation
This screen displays when you select Ethernet encapsulation.
Router