mld-snooping proxy

Function

The mld-snooping proxy command enables Multicast Listener Discovery (MLD) snooping proxy in a VLAN.

The undo mld-snooping proxy command disables MLD snooping proxy in a VLAN.

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

Format

mld-snooping proxy

undo mld-snooping proxy

Parameters

None

Views

VLAN view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

After MLD snooping is enabled, the switch forwards Report messages to router ports and broadcasts Query messages in a VLAN. The MLD snooping proxy function allows the switch to send Query messages in place of the upstream Layer 3 device and send Report/Done messages in place of downstream hosts. This saves the bandwidth on the link between the Layer 3 device and switch. The switch sends a Report/Done message 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 MLD 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.

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

Prerequisites

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

Configuration Impact

If MLD is enabled on the upstream Layer 3 device, enabling the MLD snooping proxy function on the switch may affect the querier election result. This is because the General Query messages sent by the switch may have a smaller source IP address than the General Query messages sent by the Layer 3 device. Therefore, MLD snooping proxy is not recommended on an MLD-capable multicast network.

Precautions

The configuration takes effect only after you run the mld-snooping enable command to enable MLD snooping in the VLAN.
MLD snooping proxy cannot be enabled in a VLAN if the corresponding VLANIF interface has IPv6 Layer 3 multicast function (such as MLD and IPv6 PIM) enabled.
After MLD snooping proxy is enabled in a VLAN, MLD snooping querier and MLD message suppression cannot be enabled in the VLAN.
If multicast VLAN replication is configured on the switch, the MLD snooping proxy function cannot be enabled in user VLANs.

Example

# Enable MLD snooping proxy in VLAN 100.

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