IGMP

Internet Group Management Protocol (IGMP) allows hosts on multi-access networks to inform locally attached routers of their group membership information. Hosts share their group membership information by multicasting IGMP host membership reports. Multicast routers listen for these host membership reports, and then exchange this information with other multicast routers.

The group membership reporting protocol includes two types of messages: host membership query and host membership report. IGMP messages are encapsulated in IP datagrams, with an IP protocol number of 2. Protocol operation requires that a designated querier router be elected on each subnet and that it periodically multicast a host membership query to the all-hosts group.

Hosts respond to a query by generating host membership reports for each multicast group to which they belong. These reports are sent to the group being reported, which allows other active members on the subnet to cancel their reports. This behavior limits the number of reports generated to one for each active group on the subnet. This exchange allows the multicast routers to maintain a database of all active host groups on each of their attached subnets. A group is declared inactive (expired) when no report is received for several query intervals.

The IGMPv2 protocol adds a leave group message and uses an unused field in the IGMPv1 host membership query message to specify a maximum response time. The leave group message allows a host to report when its membership in a multicast group terminates. Then, the IGMP querier router can send a group-directed query with a very small maximum response time to probe for any remaining active group members. This accelerated leave extension can reduce the time required to expire a group and prune the multicast distribution tree from minutes, down to several seconds

The unicast traceroute program allows the tracing of a path from one device to another, using mechanisms that already exist in IP. Unfortunately, you cannot apply such mechanisms to IP multicast packets. The key mechanism for unicast traceroute is the ICMP TTL exceeded message that is specifically precluded as a response to multicast packets. The traceroute facility implemented within routed conforms to the traceroute facility for IP multicast draft specification.

Gaia Embedded supports IGMP version 1, v2, and v3. Version 2 runs by default.

Gaia Embedded supports these IGMP features:

  • Multicast traceroute

  • Ability to configure protocol timers

  • Support for interfaces with secondary addresses

You can configure the these options:

  • Version number

  • Loss robustness

  • Query interval

  • Query response interval

  • Last-member query interval

Additionally, you can enable and disable router alert.

Check Point supports IGMP in a gateway as part of the support for PIM. The support of IGMP ensures synchronization of IGMP state from master to members when a new member running PIM joins the cluster.

Important - In a cluster, you must configure the routing settings separately on each Quantum Spark Cluster Member.