ZyXEL Communications GS2200 Series, Руководство пользователя

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GS2200 Series User’s Guide
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H A P T E R
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Multicast
23.1 Overview
This chapter shows you how to configure various multicast features.
Traditionally, IP packets are transmitted in one of either two ways - Unicast (1 sender to 1 recipient)
or Broadcast (1 sender to everybody on the network). Multicast delivers IP packets to just a group
of hosts on the network.
IGMP (Internet Group Management Protocol) is a network-layer protocol used to establish
membership in a multicast group - it is not used to carry user data. Refer to RFC 1112, RFC 2236
and RFC 3376 for information on IGMP versions 1, 2 and 3 respectively.
23.1.1 What You Can Do
• Use the Multicast Status screen ( Section 23.2 on page 164 ) to view multicast group
information.
• Use the Multicast Setting screen ( Section 23.3 on page 165 ) to enable IGMP snooping to
forward group multicast traffic only to ports that are members of that group.
• Use the IGMP Snooping VLAN screen ( Section 23.4 on page 168 ) to Configure how the Switch
learns multicast group membership information and add VLANs upon which the Switch is to
perform IGMP snooping.
• Use the IGMP Filtering Profile screen ( Section 23.5 on page 169 ) to specify a range of
multicast groups that clients connected to the Switch are able to join.
• Use the MVR screens ( Section 23.6 on page 170 ) to create multicast VLANs and select the
receiver port(s) and a source port for each multicast VLAN.
23.1.2 What You Need to Know
Read on for concepts on Multicasting that can help you configure the screens in this chapter.
IP Multicast Addresses
In IPv4, a multicast address allows a device to send packets to a specific group of hosts (multicast
group) in a different subnetwork. A multicast IP address represents a traffic receiving group, not
individual receiving devices. IP addresses in the Class D range (224.0.0.0 to 239.255.255.255) are
used for IP multicasting. Certain IP multicast numbers are reserved by IANA for special purposes
(see the IANA web site for more information).
IGMP Snooping
A Switch can passively snoop on IGMP packets transferred between IP multicast routers/switches
and IP multicast hosts to learn the IP multicast group membership. It checks IGMP packets passing