Igmp Configuration; About Ip Multicast Group Management - Enterasys Matrix 2G4072-52 Configuration Manual

This chapter describes the IGMP Configuration set of commands and how to use them.

10.1 ABOUT IP MULTICAST GROUP MANAGEMENT

The Internet Group Management Protocol (IGMP) runs between hosts and their immediately
neighboring multicast switch device. The protocol's mechanisms allow a host to inform its local
switch device that it wants to receive transmissions addressed to a specific multicast group.
A multicast-enabled switch device can periodically ask its hosts if they want to receive multicast
traffic. If there is more than one switch device on the LAN performing IP multicasting, one of these
devices is elected "querier" and assumes the responsibility of querying the LAN for group
members.
Based on the group membership information learned from IGMP, a switch device can determine
which (if any) multicast traffic needs to be forwarded to each of its ports. At Layer-3, multicast
switch devices use this information, along with a multicast routing protocol, to support IP
multicasting across the Internet.
IGMP provides the final step in an IP multicast packet delivery service since it is only concerned
with forwarding multicast traffic from the local switch device to group members on a directly
attached subnetwork or LAN segment.
This switch device supports IP multicast group management by
•
passively snooping on the IGMP query and IGMP report packets transferred between IP
multicast switches and IP multicast host groups to learn IP multicast group members, and
•
actively sending IGMP query messages to solicit IP multicast group members.
The purpose of IP multicast group management is to optimize a switched network's performance so
multicast packets will only be forwarded to those ports containing multicast group hosts or
multicast switch devices instead of flooding to all ports in the subnet (VLAN).

IGMP Configuration

Matrix DFE-Platinum and Diamond Series Configuration Guide
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