Configuring IGMP Snooping on Switches
Internet Group Management Protocol (IGMP) snooping constrains the flooding of IPv4 multicast traffic on VLANs on a device. With IGMP snooping enabled, the device monitors IGMP traffic on the network and uses what it learns to forward multicast traffic to only the downstream interfaces that are connected to interested receivers. The device conserves bandwidth by sending multicast traffic only to interfaces connected to devices that want to receive the traffic, instead of flooding the traffic to all the downstream interfaces in a VLAN.
You cannot configure IGMP snooping on a secondary (private) VLAN (PVLAN). However,
starting in Junos OS Release 18.3R1 on EX4300 switches and EX4300 Virtual Chassis, and Junos
OS Release 19.2R1 on EX4300 multigigabit switches, you can configure the vlan statement
at the [edit protocols igmp-snooping] hierarchy level with a primary VLAN, which implicitly
enables IGMP snooping on its secondary VLANs and avoids flooding multicast traffic on PVLANs.
See IGMP Snooping on Private
VLANs (PVLANs) for details.
Starting in Junos OS Releases 14.1X53
and 15.2, QFabric Systems support the igmp-querier statement to configure a Node
device as an IGMP querier.
The default factory configuration on legacy EX Series switches enables IGMP snooping by default on all VLANs. In this case, you don’t need any other configuration for IGMP snooping to work. However, if you want IGMP snooping enabled only on some VLANs, you can either disable the feature on all VLANs and then enable it selectively on the desired VLANs, or simply disable the feature selectively on those where you do not want IGMP snooping. You can also customize other available IGMP snooping options.
When you configure IGMP snooping using the vlan all statement (where
supported), any VLAN that is not individually configured for IGMP snooping inherits the vlan all configuration. Any VLAN that is individually configured for IGMP snooping,
on the other hand, does not inherit the vlan all configuration. Any parameters
that are not explicitly defined for the individual VLAN assume their default values, not the
values specified in the vlan all configuration. For example, in the following configuration:
protocols {
igmp-snooping {
vlan all {
robust-count 8;
}
vlan employee-vlan {
interface ge-0/0/8.0 {
static {
group 233.252.0.1;
}
}
}
}
} all VLANs except employee-vlan have a robust count of 8. Because you individually configured
employee-vlan, its robust count value is not determined by the value set under vlan all. Instead, its robust-count value is 2, the default value.
On switches without IGMP snooping enabled in the default factory configuration, you must explicitly enable IGMP snooping and configure any other of the available IGMP snooping options you want on a VLAN.
Use the following configuration steps as needed for your network to enable IGMP snooping on all VLANs (where supported), enable or disable IGMP snooping selectively on a VLAN, and configure available IGMP snooping options:
igmp-querier statement to configure a Node
device as an IGMP querier.