mld-snooping report-suppress

Function

The mld-snooping report-suppress command enables suppression of MLD Report and Done messages in a VLAN.

The undo mld-snooping report-suppress command disables suppression of MLD Report and Done messages in a VLAN.

By default, MLD Report and Done message suppression is disabled in a VLAN.

Format

mld-snooping report-suppress

undo mld-snooping report-suppress

Parameters

None

Views

VLAN view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

When a Layer 2 device receives an MLD Membership Report message (Report or Done message) from a group member, the Layer 2 device forwards the message to the directly connected Layer 3 device. A group member host sends a Membership Report message in the following situations:

When joining a multicast group, a host sends a Report message. When a multicast group has multiple members in a VLAN, the Layer 3 device receives duplicate Report messages from the member hosts.
When receiving an MLD General Query message, a host sends a Report message. Hosts use a timer to suppress duplicate Report messages on the same network segment. However, if the timer values on hosts are the same, the Layer 3 device can still receive duplicate Report messages.
When leaving a multicast group, a host sends a Done message. When a multicast group has multiple members in a VLAN, the Layer 3 device receives duplicate Done messages from the member hosts.

When MLD Report suppression is configured on the Layer 2 device, the Layer 2 device sends only one copy of MLD Report message when members join or leave a group. When the first member joins a multicast group or a host sends a Report message in response to a 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 Done message to the upstream device. The upstream device then deletes the matching forwarding entry. This reduces the number of MLD messages on the network.

Prerequisites

MLD snooping has been enabled globally using the mld-snooping_enable command.

Precautions

The configuration takes effect only after you run the mld-snooping_enable command to enable MLD snooping in the VLAN.
When receiving a Done message from a group member, the device sends Group-Specific Query messages to check whether the group has other members on the network segment.
MLD Report message suppression cannot be configured in a VLAN if the corresponding VLANIF interface has IPv6 Layer 3 multicast function (such as MLD and IPv6 PIM) enabled.
MLD snooping proxy and MLD Report message suppression cannot be configured in the same VLAN.
If multicast VLAN replication is configured, the MLD message suppression function cannot be enabled in user VLANs.
The switch can suppress duplicate Report messages even when MLD message suppression is disabled. The default suppression time is 10 seconds. To change the suppression time, run the mld-snooping suppression-time suppression-time command. If suppression-time is set to 0, all membership packets are forwarded immediately.
This function cannot suppress MLDv2 packets.

Example

# Enable suppression of Report and Done messages in VLAN 2.

<HUAWEI>system view
[HUAWEI] mld-snooping enable
[HUAWEI] vlan 2
[HUAWEI-vlan2] mld-snooping enable
[HUAWEI-vlan2] mld-snooping report-suppress