Allied Telesis AR400 manual Explanation of Multiple potential IGMP queriers

Multiple potential IGMP queriers > Explanation of Multiple potential IGMP queriers

Explanation of Multiple potential IGMP queriers

When there are no group members

Switch 1 and switch 2 are both possible Queriers, and an election determines which switch becomes the actual Querier. We can see the results of the election by using the command show ip igmp on each switch.

Manager Switch 1> show ip igmp
IGMP Protocol
------------------------------------------------------------------------
Status	Enabled
Default Query Interval	125 secs
Default Timeout Interval	260 secs
Last Member Query Interval	....... 10 (1/10secs)
Last Member Query Count	2
Robustness Variable	2
Query Response Interval	100 (1/10secs)
Disabled All-groups ports	None
Interface Name	vlan100
Other Querier timeout ... 209 secs
Group List
------------------------------------------------------------------------

Manager Switch 2> show ip igmp
IGMP Protocol
------------------------------------------------------------------------
Status		Enabled
Default Query Interval		125 secs
Default Timeout Interval		260 secs
Last Member Query Interval	.......	10 (1/10secs)
Last Member Query Count		2
Robustness Variable		2
Query Response Interval		100 (1/10secs)
Disabled All-groups ports	........	None
Interface Name	vlan100	(DR)
IGMP Proxy	Off
Group List
------------------------------------------------------------------------

In the output from switch 2 above, switch 2 reports that it has become the Querier by displaying (DR)—which stands for Designated Router—next to the interface name.

In the output from switch 1 above, switch 1 has an entry for Other Querier timeout, which indicates that it is aware that another device is the IGMP Querier. If the timer expires, switch 1 will decide that the other Querier no longer exists, and will become the Querier itself. The timer is refreshed by a Membership Query or an IGMP Querier election.

Note: Switch 2 shows an IGMP Proxy entry, which is set to Off (see "IGMP proxy" on page 21). Switch 1 does not show a Proxy entry because the AT-8948 did not support IGMP Proxy on Software Version 2.7.6 which this example used.

Page 17 AlliedWare™ OS How To Note: IGMP