Multimedia Traffic Control with IP Multicast (IGMP)

More on IGMP Operation

For web-based help on how to use the web browser interface screen, click on the ��� button provided on the web browser screen.

More on IGMP Operation

Multicast traffic management uses switches, multicast routers, and hosts that support IGMP. (In Hewlett-Packard’s implementation of IGMP, a multicast router is not necessary as long as a switch is configured to support IGMP with the querier feature enabled.) The multicast group running version 2 of IGMP uses three fundamental types of messages to communicate:

Query: A message sent from the querier (multicast router or switch) asking for a response from each host belonging to the multicast group. If a multicast router supporting IGMP is not present, then the switch must assume this function in order to elicit group membership information from the hosts on the network. (If you need to disable the querier feature, you can do so through the CLI, using the IGMP configuration MIB. Refer to “Configuring the Querier Capability” on page 12-9.)

Report (Join): A message sent by a host to the querier to indicate that the host wants to be or is a member of a given group indicated in the report message.

Leave Group: A message sent by a host to the querier to indicate that the host has ceased to be a member of a specific multicast group.

Thus, IGMP identifies members of a multicast group (within a subnet) and allows IGMP-configured hosts (and routers) to join or leave multicast groups.

IGMP Data. To display data showing active group addresses, reports, que­ ries, querier access port, and active group address data (port, type, and access), see “IP Multicast (IGMP) Status” on page B-18.

12-10