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508 CHAPTER 34: CONFIGURING IGMP
The default maximum query response time is 10 seconds but ranges from 1 to 25
seconds.
This configuration can only be carried out if the current router interface is
operating IGMP Version 2.
Configuring Subnet
Querier Survival Time
When there are several routers operating IGMP in a subnet, one router is chosen
to serve as a querier to take charge of sending query messages to other routers in
the network segment. In the network initialization, all the routers in the network
segment act as querier by default, and send general query messages to all the
multicast hosts in the subnet the routers connect to. Meanwhile, they compare
the receiving IP address of the query message interface with the sending IP address
of the query message interface. The router with the minimum IP address in the
subnet will be chosen as querier, and the other routers become non-queriers.
All the non-queriers start the other querier present interval timer. Before the timer
times out, if the query message from the querier is received, the timer resets. If the
timer times out, all the routers reset as querier. The querier selection process
restarts.
Make the following configuration in the interface view.
Table 581 Configure Subnet Querier Survival Time
By default, subnet querier timeout is 250 seconds.
This configuration can only be carried out if the current router interface is
operating IGMP Version 2.
Displaying and
Debugging IGMP
Table 582 Display and Debug IGMP
After the previous configuration, execute the display command in all views to
display IGMP configuration, and to verify the effect of the configuration. Execute
the debugging command in system view to debug IGMP.
IGMP Configuration
Example
Router A, Router B and a PC connect to one another through a Hub, and their
interfaces are all fast Ethernet (FE).
Restore the default value of IGMP
maximum query response time
undo igmp max-response-time
Operation Command
Configure subnet Querier survival time igmp timer querier-present seconds
Restore the default value of the subnet
Querier survival time
undo igmp timer querier-present
Operation Command
Display the group membership status in
the direct connecting subnet
display igmp group [ group-address |
interface type number ]
Display IGMP interface configuration
information
display igmp interface [ type number
]
Turn on the switch of IGMP debugging
information
debugging igmp { all | event | host |
packet | timer }