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Example: 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.

This example describes how to configure IGMP snooping:

Requirements

This example requires Junos OS Release 11.1 or later on a QFX Series product.

Before you configure IGMP snooping, be sure you have:

  • Configured the employee-vlan VLAN

  • Assigned interfaces ge-0/0/1, ge-0/0/2, ge-0/0/3, and ge-0/0/4 to employee-vlan

Overview and Topology

In this example you configure an interface to receive multicast traffic from a source and configure some multicast-related behavior for downstream interfaces. The example assumes that IGMP snooping was previously disabled for the VLAN.

Figure 1: IGMP snooping on a switch IGMP snooping on a switch

By enabling IGMP snooping on a switch, interfaces can be either host-only interfaces or multicast-router interfaces. If the interfaces are not configured explicitly, through IGMP snooping the switch learns which interfaces are host-only and which ones are multicast-router interfaces.

Topology

Table 1 shows the components of the topology for this example.

Table 1: Components of the IGMP Snooping Topology

Components

Settings

VLAN name

employee-vlan, tag 20

Interfaces in employee-vlan

ge-0/0/1, ge-0/0/2, ge-0/0/3, ge-0/0/4

Multicast IP address for employee-vlan

225.100.100.100

Configuration

To configure basic IGMP snooping on a switch:

Procedure

CLI Quick Configuration

To quickly configure IGMP snooping, copy the following commands and paste them into a terminal window:

Step-by-Step Procedure

Configure IGMP snooping:

  1. Enable and configure IGMP snooping on the VLAN employee-vlan:

  2. Optionally, you can configure an interface to belong to a multicast group. For example, for testing IGMP snooping with Layer 2 multicast forwarding, you might assign an interface to a static multicast group:

    (See static (IGMP Snooping) for more on how static groups work at Layer 2.)

  3. Configure an interface to forward IGMP queries received from multicast routers.

  4. Configure the switch to wait for four timeout intervals before timing out a multicast group on a VLAN:

Results

Check the results of the configuration:

Related Documentation