ZyXEL Communications IES-2000, Руководство пользователя

Страница: 277 / 304

IES-2000/3000 User’s Guide
IP Commands 29-1
Chapter 29
IP Commands
This chapter discusses configuring the VLC1012 using IP commands.
29.1 Introduction
Traditionally, IP packets are transmitted in one of either two ways - Unicast (one sender to one recipient) or
Broadcast (one sender to everybody on the network). Multicast delivers IP packets to just a group of hosts on the
network.
IGMP (Internet Group Multicast Protocol) is a session-layer protocol used to establish membership in a multicast
group - it is not used to carry user data. Refer to
RFC 1112 and RFC 2236 for information on IGMP versions 1
and 2 respectively.
A layer-2 switch can passively snoop on IGMP Query, Report and Leave (IGMP version 2) packets transferred
between IP multicast routers/switches and IP multicast hosts to learn the IP multicast group membership. It checks
IGMP packets passing through it, picks out the group registration information, and configures multicasting
accordingly.
Without IGMP snooping, multicast traffic is treated in the same manner as broadcast traffic, that is, it is forwarded
to all ports. With IGMP snooping, group multicast traffic is only forwarded to ports that are members of that
group. IGMP Snooping generates no additional network traffic, allowing you to significantly reduce multicast
traffic passing through your switch.
The following table is a summary of the IGMP snooping IP commands supported. Please see the section on SMT
menu 2 for more information on IGMP snooping.
Table 29-1 IP Commands Supported
COMMAND DESCRIPTION
ip igmpsnoop status This command shows IGMP snooping information such as
status, packet counters and joined multicast groups.
ip igmpsnoop querier This command shows the incoming channel from which the
last query came.
ip igmpsnoop enable This command turns on IGMP snooping.
ip igmpsnoop disable This command turns off IGMP snooping.
29.1.1 IGMP Snooping Status
Syntax:
ip igmpsnoop status