Igmp Multicast Addresses; Igmp Versions - Cisco Catalyst 3850 series Configuration Manual

IGMP Multicast Addresses

• A querier is a network device, such as a router, that sends query messages to discover which network
• A host is a receiver, including routers, that sends report messages (in response to query messages) to
Hosts identify group memberships by sending IGMP messages to their local multicast device. Under IGMP,
devices listen to IGMP messages and periodically send out queries to discover which groups are active or
inactive on a particular subnet.
IGMP Multicast Addresses
IP multicast traffic uses group addresses, which are Class D IP addresses. The high-order four bits of a Class
D address are 1110. Therefore, host group addresses can be in the range 224.0.0.0 to 239.255.255.255.
Multicast addresses in the range 224.0.0.0 to 224.0.0.255 are reserved for use by routing protocols and other
network control traffic. The address 224.0.0.0 is guaranteed not to be assigned to any group.
IGMP packets are transmitted using IP multicast group addresses as follows:
• IGMP general queries are destined to the address 224.0.0.1 (all systems on a subnet).
• IGMP group-specific queries are destined to the group IP address for which the device is querying.
• IGMP group membership reports are destined to the group IP address for which the device is reporting.
• IGMPv2 leave-group messages are destined to the address 224.0.0.2 (all devices on a subnet).
• IGMPv3 membership reports are destined to the address 224.0.0.22; all IGMPv3-capable multicast
Related Topics
Configuring the Device as a Member of a Group (CLI), on page 45
Example: Configuring the Device as a Member of a Multicast Group, on page 93

IGMP Versions

The device supports IGMP version 1, IGMP version 2, and IGMP version 3. These versions are interoperable
on the device. For example, if IGMP snooping is enabled and the querier's version is IGMPv2, and the device
receives an IGMPv3 report from a host, then the device can forward the IGMPv3 report to the multicast router.
An IGMPv3 device can receive messages from and forward messages to a device running the Source Specific
Multicast (SSM) feature.
Related Topics
Changing the IGMP Version(CLI), on page 49
Restrictions for Configuring IGMP, on page 32
Restrictions for IGMP Snooping, on page 33
IP Multicast Routing Configuration Guide, Cisco IOS XE Release 3.6E (Catalyst 3850 Switches)
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devices are members of a given multicast group.
inform the querier of a host membership. Hosts use IGMP messages to join and leave multicast groups.
devices must listen to this address.
Configuring IGMP
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