(Revised 2011-07-13)
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IGMP Snooping
In factory defaults, IGMP Snooping is enabled, and the switch is
Plug and Play
for IGMP. IGMP snooping
provides intelligent network support for multicast applications. In particular, unneeded traffic is reduced.
IGMP Snooping is configured via the console and if enabled, then operates dynamically upon each power up
and until entering escape to the console terminates it. Also, there can be manual only or manual and
dynamic operation (as described below). Note that “static filters” („sfilter‟ below) can be used whether
IGMP Snooping is enabled or not. At the end of this section, see “Example of an IGMP info screen “ for a
summary example.
Command
Description
Comment
info
Displays the current
IGMP settings.
disable (or
enable)
Enable ro Disable
IGMP
Choice is opposite of current state
routers
Manage Router Port(s)
for IGMP Snooping
Router Ports can be manually set
and/or auto-detected.
rfilters
Manage Router
Multicast Data Filters
Router ports can get or not get the
IGMP group data (as opposed to
controls like joins, leaves, and
queries).
query
Manage Query
Generation
Query Generation can be manually
set and/or automatically done.
Out of the box
, IGMP Snooping will function dynamically without intervention. If some of the devices in
the LAN do not understand IGMP, then manual settings are provided to accommodate them.
The Internet Group Management Protocol (IGMP) is a protocol that provides a way for a computer to report
its multicast group membership to adjacent „routers‟. In this case N-Tron 500 series –A switches provide
router-like functionality
. Multicasting allows one computer to send content to multiple other computers
that have identified themselves as interested in receiving the originating computer's content. Multicasting can
be used to transmit only to an audience that has joined (and not left) a multicast group membership. IGMP
version 2 is formally described in the Internet Engineering Task Force (IETF) Request for Comments (RFC)
2236. IGMP version 1 is formally described in the Internet Engineering Task Force (IETF) Request for
Comments (RFC) 1112. The 500 series supports v1 and v2.
Example of the IGMP router management screen:
CLI\SWITCH\IGMP>routers
For IGMP Snooping, router ports mode is auto.
Manually Selected Router Port(s): none
Automatically detected Router Port(s): none
Enter: <(ESC)> to keep this configuration, OR
'A' to Auto-detect plus manual, OR
'M' for Manual only, OR
'N' for None.
Enter A, M, N , (or ESC to exit) >
