Understanding Igmp Snooping And Multicast - Dell PowerConnect J-EX4200-24T Software Manual

CHAPTER 75
Understanding IGMP Snooping and
Multicast
IGMP Snooping on J-EX Series Switches Overview
How IGMP Snooping Works
IGMP Snooping on J-EX Series Switches Overview on page 2047
Understanding Multicast VLAN Registration on J-EX Series Switches on page 2052
Internet Group Management Protocol (IGMP) snooping regulates multicast traffic in a
switched network. With IGMP snooping enabled, a LAN switch monitors the IGMP
transmissions between a host (a network device) and a multicast router, keeping track
of the multicast groups and associated member interfaces. The switch uses that
information to make intelligent multicast-forwarding decisions and forward traffic to the
intended destination interfaces. J-EX Series Switches support IGMPv1, IGMPv2, and
IGMPv3.
For details on IGMPv1, IGMPv2, and IGMPv3, see the following standards:
For IGMPv1, see RFC 1112, Host extensions for IP multicasting at
http://www.faqs.org/rfcs/rfc1112.html
For IGMPv2, see RFC 2236, Internet Group Management Protocol, Version 2 at
http://www.faqs.org/rfcs/rfc2236.html
For IGMPv3, see RFC 3376, Internet Group Management Protocol, Version 3 at
http://www.faqs.org/rfcs/rfc3376.html
This IGMP snooping topic covers:
How IGMP Snooping Works on page 2047
How IGMP Snooping Works with Routed VLAN Interfaces on page 2048
How Hosts Join and Leave Multicast Groups on page 2051
IGMP Snooping Support for IGMPv3 on page 2051
A J-EX Series switch usually learns unicast media access control (MAC) addresses by
checking the source address field of the frames it receives. However, a multicast MAC
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2047