Allied Telesis AR400 manual Note that the group list is sorted by refresh time, not group address

IGMP throttling (limiting the number of streams for each subscriber) > Explanation of IGMP throttling (limiting the number of streams

When switch 2 drops groups by throttling, it does not send a Leave message, because IGMP snooping cannot generate IGMP packets. Therefore, the Querier (switch 1) still believes that switch 2 is interested in the throttled groups, as output from the command show ip igmp on switch 1 shows.

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	(DR)
Group List
Group. 224.12.13.13			Last Adv. 172.31.0.222		Refresh time 215 secs
Ports	49
Group. 224.12.13.14			Last Adv. 172.31.0.222		Refresh time 215 secs
Ports	49
Group. 224.12.13.15			Last Adv. 172.31.0.222		Refresh time 215 secs
Ports	49
Group. 224.12.13.16			Last Adv. 172.31.0.222		Refresh time 215 secs
Ports	49
Group. 224.12.13.17			Last Adv. 172.31.0.222		Refresh time 217 secs
Ports	49
Group. 224.12.13.18			Last Adv. 172.31.0.222		Refresh time 217 secs
Ports	49
Group. 224.12.13.19			Last Adv. 172.31.0.222		Refresh time 217 secs
Ports	49
Group. 224.12.13.11			Last Adv. 172.31.0.222		Refresh time 238 secs
Ports	49
Group. 224.12.13.12			Last Adv. 172.31.0.222		Refresh time 238 secs
Ports	49

------------------------------------------------------------------------

This can cause the Querier to temporarily send more groups than necessary to a switch. The older groups will eventually time out.

Note that the group list is sorted by refresh time, not group address.

The output above also shows that the IGMP Querier only records the IP address of the last interested client—the Last Adv field shows the IP of the client who last sent an IGMP

Page 45 AlliedWare™ OS How To Note: IGMP