5INTERNET GROUP MANAGEMENT
PROTOC OL (IGMP) SNOOPI NG
This chapter provides the following information about IGMP snooping:
■Overview
■CoreBuilder 5000 Support
■Locating Multicast Routers in the Network
■No Multicast Route rs on the Network
■Enabling IGMP Snooping on CoreBuilder 5000 SwitchModules
Overview The Internet Group Management Protocol (IGMP) runs between hosts
and their immediate neighboring multicast routers. This protocol is not
a client/server protocol, but rather a routing protocol.
Through IGMP, a host to inform its local router that it wants to receive
transmissions that are addressed to a specific multicast group. Also,
routers periodically query the LAN to determine if known group members
are still active.
Based on the group membership information lear ned from the IGMP, a
router can determine which (if any) multicast traffic needs to be
forwarded to each of its subnetworks. Multicast routers use this
information in conjunction with a multicast routing protocol to support IP
multicasting across the Internet. Layer 2 switches flood multicast packets
to all ports without the presence of management specified filters.