ZyXEL Communications Corporation NBG6503 Manuel D’Utilisation

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 Chapter 11 WAN
NBG6503 User’s Guide
101
11.3.2  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 72   
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 Router supports both IGMP version 1 
(IGMP-v1) and IGMP version 2 (IGMP-v2). 
At start up, the Router queries all directly connected networks to gather group membership. After 
that, the Router periodically updates this information. IP multicasting can be enabled/disabled on 
the Router LAN and/or WAN interfaces in the Web Configurator (LAN; WAN). Select None to 
disable IP multicasting on these interfaces.
Router