IGMP Overview
The IPv4 address scheme assigns class D addresses for IP multicast. IGMP is the protocol
that uses these addresses, which can be in the range 224.0.0.0 to 239.255.255.255. The
following addresses have specific functions or are unavailable:
•
224.0.0.0 is reserved—you cannot assign it to a group.
•
224.0.0.1 is the all-hosts address—a packet sent to this address reaches all hosts on
a subnet.
•
224.0.0.2 is the all-routers address—a packet sent to this address reaches all routers
on a subnet.
This implementation of IGMP complies with IGMP versions 1, 2, and 3. IGMPv3 supports
source-specific join and leave messages and is backward compatible with IGMPv1 and
IGMPv2.
IGMPv2 mode interfaces exchange the following types of messages between routers
and hosts:
•
Group membership queries
•
Group membership reports
•
Leave group membership messages
IGMPv3 mode interfaces exchange the following types of messages with IGMPv3 hosts:
•
Group membership queries
•
IGMPv3 group membership reports
Group Membership Queries
A multicast router can be a querier or a nonquerier. Only one querier is on a network at
any time. Multicast routers monitor queries from other multicast routers to determine
the status of the querier. If the querier detects a query from a router with a lower IP
address, it relinquishes its role to that router.
IGMPv1 and IGMPv2 mode interfaces send two types of group membership queries to
hosts on the network:
•
General queries to the all-hosts group address (224.0.0.1)
•
Specific queries to the appropriate multicast group address
IGMPv3 mode interfaces send the following types of queries to IGMPv3 hosts:
•
General queries
•
Group-specific queries
•
Source-specific queries
Copyright © 2010, Juniper Networks, Inc.42
JunosE 11.2.x Multicast Routing Configuration Guide
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