ExtremeXOS® Command Reference Guide

enable igmp snooping {forward-mcrouter-only | {vlan} name | with-proxy vr vrname}

Description

Enables IGMP snooping on one or all VLANs.

Syntax Description


forward-mcrouter-only	Specifies that the switch forward all multicast traffic to the multicast router only.
`name`	Specifies a VLAN or VMAN on which to enable IGMP snooping.
with-proxy vr `vrname`	Controls how join and leave messages are forwarded from the specified virtual router. If this option is specified, one join message per query is forwarded, and a leave message is forwarded only if it is from the last receiver on the VLAN.

Default

Enabled.

Usage Guidelines

This command applies to both IGMPv2 and IGMPv3.

IGMP snooping is enabled by default on the switch. If you are using multicast routing, IGMP snooping can be enabled or disabled. If IGMP snooping is disabled, all IGMP and IP multicast traffic floods within a given VLAN or VMAN.

The forward-mcrouter-only, vlan, and with-proxy options control three separate and independent features. You can manage one feature at a time with this command, and you can enter the command multiple times as needed to control each feature. For example, you can enter the command twice to enable both the forward-mcrouter-only and with-proxy options.

If a VLAN or VMAN name is specified with this command, IGMP snooping is enabled only on that VLAN or VMAN. If no options are specified, IGMP snooping is enabled on all VLANs.

Note

IGMP snooping is not supported on SVLANs on any platform.

The with-proxy option enables the IGMP snooping proxy feature, which reduces the number of join and leave messages forwarded on the virtual router as described in the table above. This feature is enabled by default.

An optional optimization for IGMP snooping is the strict recognition of routers only if the remote devices are running a multicast protocol. Two IGMP snooping modes are supported:

The forward-mcrouter-only mode forwards all multicast traffic to the multicast router (that is, the router running PIM, DVMRP or CBT).
When not in the forward-mcrouter-only mode, the switch forwards all multicast traffic to any IP router (multicast or not), and any active member port to the local network that has one or more subscribers.
Note
The forward-mcrouter-only mode for IGMP snooping is enabled/disabled on a switch-wide basis, not on a per-VLAN basis. In other words, all the interfaces enabled for IGMP snooping are either in the forward-mcrouter-only mode or in the non-forward-mcrouter-only mode, and not a mixture of the two modes.

To change the snooping mode you must disable IP multicast forwarding. To disable IP multicast forwarding, use the command:

disable ipmcforwarding {vlan name}

To change the IGMP snooping mode from the non-forward-mcrouter-only mode to the forward-mcrouter-only mode, use the commands:

disable ipmcforwarding

enable igmp snooping forward-mcrouter-only

enable ipmcforwarding {vlan name}

To change the IGMP snooping mode from the forward-mcrouter-only mode to the non-forward-mcrouter-only mode, use the commands:

disable ipmcforwarding

disable igmp snooping forward-mcrouter-only

enable ipmcforwarding {vlan name}

History

This command was first available in ExtremeXOS 10.1.

Platform Availability

This command is available on platforms that support the appropriate license. For complete information about software licensing, including how to obtain and upgrade your license and which licenses support the IGMP snooping feature, see the ExtremeXOS 30.7 Feature License Requirements document.

enable igmp snooping