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Using a Switch as an IGMP Querier

If IGMP snooping is enabled on a pure Layer 2 a local network (that is, Layer 3 is not enabled on the network), and there is not multicast router in the network, multicast traffic might not be properly forwarded through the network. This problem occurs if the local network is configured such that multicast traffic must be forwarded between switches in order to reach a multicast receiver. In this case, an upstream switch does not forward multicast traffic to a downstream switch (and therefore to the multicast receivers attached to the downstream switch) because the downstream switch does not forward IGMP reports to the upstream switch. You can solve this problem by configuring one of the switches to be an IGMP querier. This switch sends periodic general query packets to all the switches in the network, which ensures that the snooping membership tables are updated and prevents any multicast traffic loss.

If you configure multiple switches to be IGMP queriers, the switch with the lowest (smallest) IGMP querier source address takes precedence and acts as the querier. Switches with higher IGMP querier source addresses stop sending IGMP queries unless they do not receive IGMP queries for 255 seconds. If a switch with a higher IGMP querier source address does not receive any IGMP queries during that period, it starts sending queries again.

Note: The igmp-querier statement is supported on QFabric systems in Junos OS 14.1X53-D15 but is not supported in Junos OS 15.1.

Starting in Junos OS 15.1, the igmp-querier statement is not supported on QFX systems. The statement is supported on QFX systems in Junos OS 15.2 and following.

To configure a standalone switch to act as an IGMP querier, enter the following:

[edit protocols]
user@switch# set igmp-snooping vlan vlan-name l2-querier source-address source address

To configure a QFabric Node device to act as an IGMP querier, enter the following:

[edit protocols]
user@switch# set igmp-snooping vlan vlan-name igmp-querier source-address source address
 

Related Documentation

 

Release History Table

Release
Description
15.1
The igmp-querier statement is supported on QFabric systems in Junos OS 14.1X53-D15 but is not supported in Junos OS 15.1.
15.1
Starting in Junos OS 15.1, the igmp-querier statement is not supported on QFX systems. The statement is supported on QFX systems in Junos OS 15.2 and following.

Modified: 2016-11-15

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