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506 CHAPTER 34: CONFIGURING IGMP
IGMP is asymmetric between hosts and routers. The host responds to the IGMP
query message of the multicast router, and makes a response in the membership
report message. The router periodically sends a general query message. Then it
determines, based on the response message received, whether a specific group
has a host access on its own subnet. Meanwhile, when a router exits from a
group, it sends a message to the multicast router when it exits. When it receives
the message, the multicast router sends a packet to inquire about the group to
ensure that the member has already gone.
Configuring IGMP To configure the IGMP protocol, the multicast routing function is first enabled, and
then each feature of the IGMP protocol can be configured.
IGMP configuration includes tasks that are covered in the following sections:
■ Enabling Multicast Routing
■ Configuring Router Interfaces as Group Members
■ Configuring the Version Number of IGMP at the Router Interface
■ Configuring the Time Interval of IGMP Host Sending Query Messages
■ Configuring IGMP Maximum Query Response Time
■ Configuring Subnet Querier Survival Time
Enabling Multicast
Routing
Start the IGMP protocol on all interfaces to enable routers to send multicast
messages. Only after enabling multicast routing can all the other configurations
related to the multicast be valid.
Make the following configuration in system view.
Table 576 Enable/disable Multicast Routing
By default, the system disables multicast routing.
Configuring Router
Interfaces as Group
Members
Configuring router interfaces as group members can not only enable routers to
access the multicast group by simulating host behaviors, but also enables the static
multicast group to access the multicast group.
Make the following configuration in the interface view.
Table 577 Configure Router Interfaces to be Group Members
By default, the router interface has no group member.
Operation Command
Enable multicast routing multicast routing-enable
Disable multicast routing undo multicast routing-enable
Operation Command
Configure router interface to be group
members
igmp host-join groups-address
Delete router interface from group
members
undo igmp host-join groups-address