Allied Telesis AR400 manual When a client joins a group, Page 18 AlliedWare OS How To Note IGMP

Multiple potential IGMP queriers > Explanation of Multiple potential IGMP queriers

When a client joins a group

Now imagine that Client 1 sends a Membership Report to switch 2 for the group

224.12.13.14. If we check the group membership for switch 2 by using the command show igmpsnooping, we see a group entry for 224.12.13.14.

Manager Switch 2> show igmpsnooping

IGMP Snooping

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

Status			Enabled
Disabled All-groups		ports	........ None
Vlan	Name (vlan id)	..... default (1)
Fast	Leave		Off
Group List
No	group memberships.
Vlan	Name (vlan id)	..... vlan100 (100)
Fast	Leave		Off

Group List
Group. 224.12.13.14	Entry timeout 225 secs
Ports 2

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

If we check the group membership for switches 1 and 3, we see no entries for 224.12.13.14, but see an All Groups entry on each switch. The All Groups entry points to the Querier, switch 2. The output for switch 1, for example, shows port 49 as the All Groups port, indicating that switch 1 reaches the Querier via port 49.

Manager Switch 1> show igmpsnooping

IGMP Snooping

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

Status			Enabled
Disabled All-groups		ports	........ None
Vlan	Name (vlan id)	..... default (1)
Fast	Leave		Off
Group List
No	group memberships.
Vlan	Name (vlan id)	..... vlan100 (100)
Fast	Leave		Off

Group	List
Group. 224.12.13.14			Entry timeout	25 secs
Ports		None
All	Groups		Entry timeout	177 secs
Ports		49

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

Note: An All Groups port does not necessarily indicate that an IGMP Querier can be found via that port—it could be a router instead. See "Controlling which addresses create All Groups entries" on page 95 for more information.

Page 18 AlliedWare™ OS How To Note: IGMP