Concept Guide

Internet address is 1.1.1.1/24
IGMP is enabled on interface
IGMP query interval is 60 seconds
IGMP querier timeout is 125 seconds
IGMP max query response time is 10 seconds
IGMP last member query response interval is 1000 ms
IGMP immediate-leave is disabled
IGMP activity: 0 joins, 0 leaves, 0 channel joins, 0 channel leaves
IGMP querying router is 1.1.1.1 (this system)
IGMP version is 3
Viewing IGMP Groups
To view both learned and statically congured IGMP groups, use the following command.
• View both learned and statically congured IGMP groups.
EXEC Privilege mode
show ip igmp groups
show ipv6 mld groups
Example of the show ip igmp groups Command
DellEMC# show ip igmp groups
Total Number of Groups: 2
IGMP Connected Group Membership
Group Address Interface Mode Uptime Expires Last Reporter
225.1.1.1 TenGigabitEthernet 1/1 IGMPV2 00:11:19 00:01:50 165.87.34.100
225.1.2.1 TenGigabitEthernet 1/1 IGMPV2 00:10:19 00:01:50 165.87.31.100
Dell#show ipv6 mld groups
Total Number of Groups: 1
MLD Connected Group Membership
Group Address Interface Mode Uptime Expires Last Reporter
Ff08::12 Vlan 10 MLDv2 00:00:12 00:02:05 1::2
Adjusting Timers
The following sections describe viewing and adjusting timers.
To view the current value of all IGMP timers, use the following command.
• View the current value of all IGMP timers.
EXEC Privilege mode
show ip igmp interface
For more information, refer to the example shown in Viewing IGMP Enabled Interfaces.
Adjusting Query and Response Timers
The querier periodically sends a general query to discover which multicast groups are active. A group must have at least one host to be
active.
When a host receives a query, it does not respond immediately, but rather starts a delay timer. The delay time is set to a random value
between 0 and the maximum response time. The host sends a response when the timer expires; in version 2, if another host responds
before the timer expires, the timer is nullied, and no response is sent.
The maximum response time is the amount of time that the querier waits for a response to a query before taking further action. The querier
advertises this value in the query (refer to the illustration in IGMP Version 2). Lowering this value decreases leave latency but increases
response burstiness because all host membership reports must be sent before the maximum response time expires. Inversely, increasing
this value decreases burstiness at the expense of leave latency.
Internet Group Management Protocol (IGMP)
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