igmp-snooping proxy

Function

The igmp-snooping proxy command enables IGMP snooping proxy in a VLAN.

The undo igmp-snooping proxy command disables IGMP snooping proxy in a VLAN.

By default, IGMP snooping proxy is disabled in a VLAN.

Format

igmp-snooping proxy

undo igmp-snooping proxy

Parameters

None

Views

VLAN view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

After IGMP snooping is enabled on a switch, the switch forwards Query messages from the upstream IGMP querier and Report/Leave messages from downstream hosts without changing the messages. When there are a large number of hosts on a network, redundant IGMP messages overload the upstream device. Enabling the IGMP snooping proxy function on the switch can solve this problem. This function allows the switch to send IGMP Query messages in place of the upstream Layer 3 device and send Report/Leave messages in place of downstream hosts, conserving link bandwidth between the Layer 3 device and switch. The switch sends IGMP Report/Leave messages to the upstream Layer 3 device only in the following situations:

When the first member joins a multicast group or a host sends a Report message in response to an IGMP Query message, the Layer 2 device forwards a Report message to the upstream device. The upstream device can create or maintain the matching forwarding entry based on the Report message.
When the last member of a multicast group leaves the group, the Layer 2 device forwards a Leave message to the upstream device. The upstream device then deletes the matching forwarding entry.

An upstream Layer 3 device does not send Query messages as a querier when IGMP is not enabled, for example, the Layer 3 device has only static multicast groups. In this case, the switch cannot create or maintain group memberships even though IGMP snooping is enabled. The IGMP snooping proxy function enables the switch to send Query messages to downstream hosts. For the hosts, the switch is a querier.

Prerequisites

IGMP snooping has been enabled globally using the igmp-snooping enable (system view) command.

Configuration Impact

If IGMP is enabled on the upstream Layer 3 device, enabling the IGMP snooping proxy function on the switch may affect the querier election result, because the General Query messages sent by the switch have a smaller source IP address than the General Query messages sent by the Layer 3 device. To solve this problem, run the igmp-snooping proxy-uplink-port command to prevent the switch from sending Query messages to the uplink interface connected to the upstream device. Alternatively, run the igmp-snooping send-query source-address command to set a large source IP address for Query messages.

Precautions

The configuration takes effect only after you run the igmp-snooping enable (VLAN view) command to enable IGMP snooping in the VLAN.
IGMP snooping proxy cannot be enabled in a VLAN if the corresponding VLANIF interface has Layer 3 multicast function (such as IGMP and PIM) enabled.
After enabling IGMP snooping proxy in a VLAN, do not enable IGMP snooping querier or IGMP message suppression in the VLAN because these functions conflict.
If multicast VLAN replication is configured on the switch, the IGMP snooping proxy function cannot be enabled in user VLANs.

Example

# Enable IGMP snooping proxy in VLAN 100.

<HUAWEI> system-view
[HUAWEI] igmp-snooping enable
[HUAWEI] vlan 100
[HUAWEI-vlan100] igmp-snooping enable
[HUAWEI-vlan100] igmp-snooping proxy