MLD Snooping Querier Commands

In an IPv6 environment, MLD Snooping requires that one central switch or router periodically query all end-devices on the network to announce their multicast memberships. This central device is the MLD Querier. The MLD query responses, known as MLD reports, keep the switch updated with the current multicast group membership on a port-by-port basis. If the switch does not receive updated membership information in a timely fashion, it will stop forwarding multicasts to the port where the end device is located.

This section describes the commands you use to configure and display information on MLD Snooping queries on the network and, eparately, on VLANs.

set mld querier

Use this command to enable MLD Snooping Querier on the system (Global Config Mode) or on a VLAN. Using this command, you can specify the IP address that the snooping querier switch should use as a source address while generating periodic queries.

If a VLAN has MLD Snooping Querier enabled and MLD Snooping is operationally disabled on it, MLD Snooping Querier functionality is disabled on that VLAN. MLD Snooping functionality is re-enabled if MLD Snooping is operational on the VLAN.

The MLD Snooping Querier sends periodic general queries on the VLAN to solicit membership reports.

• Default: disabled
• Format: set mld querier [vlan-id] [address ipv6_address]
• Mode:
  • Global Config
  • VLAN Mode

no set mld querier

Use this command to disable MLD Snooping Querier on the system. Use the optional parameter address to reset the querier address.

• Format: no set mld querier [vlan-id][address]
• Mode:
  • Global Config
  • VLAN Mode

set mld querier query-interval

Use this command to set the MLD Querier Query Interval time. It is the amount of time in seconds that the switch waits before sending another general query.

• Default: disabled
• Format: set mld querier query_interval <1-18000>
• Mode: Global Config

no set mld querier query-interval

Use this command to set the MLD Querier Query Interval time to its default value.

• Format: no set mld querier query_interval
• Mode: Global Config

set mld querier timer expiry

Use this command to set the MLD Querier timer expiration period. It is the time period that the switch remains in Non-Querier mode once it has discovered that there is a Multicast Querier in the network.

• Default: 60 seconds
• Format: set mld querier timer expiry <60-300>
• Mode: Global Config

no set mld querier timer expiry

Use this command to set the MLD Querier timer expiration period to its default value.

• Format: no set mld querier timer expiry
• Mode: Global Config

set mld querier election participate

Use this command to enable the Snooping Querier to participate in the Querier Election process when it discovers the presence of another Querier in the VLAN. When this mode is enabled, if the Snooping Querier finds that the other Querier’s source address is better (less) than the Snooping Querier’s address, it stops sending periodic queries. If the Snooping Querier wins the election, then it will continue sending periodic queries.

• Default: disabled
• Format: set mld querier election participate
• Mode: VLAN Config

no set mld querier election participate

Use this command to set the snooping querier not to participate in querier election but go into a non-querier mode as soon as it discovers the presence of another querier in the same VLAN.

• Format: no set mld querier election participate
• Mode: VLAN Config

show mldsnooping querier

Use this command to display MLD Snooping Querier information. Configured information is displayed whether or not MLD Snooping Querier is enabled.

• Format: show mldsnooping querier [{detail | vlan vlanid}]
• Mode: Privileged EXEC

When the optional arguments vlandid are not used, the command displays the following information.

• Admin Mode: Indicates whether or not MLD Snooping Querier is active on the switch.
• Admin Version: Indicates the version of MLD that will be used while sending out the queries. This is defaulted to MLD v1 and it cannot be changed.
• Querier Address: Shows the IP address which will be used in the IPv6 header while sending out MLD queries. It can be configured using the appropriate command.
• Query Interval: Shows the amount of time in seconds that a Snooping Querier waits before sending out the periodic general query.
• Querier Timeout: Displays the amount of time to wait in the Non-Querier operational state before moving to a Querier state.

When you specify a value for vlanid, the following information appears.

• VLAN Admin Mode: Indicates whether MLD Snooping Querier is active on the VLAN.
• VLAN Operational State: Indicates whether MLD Snooping Querier is in "Querier" or "Non-Querier" state. When the switch is in Querier state, it will send out periodic general queries. When in Non-querier state, it will wait for moving to Querier state and does not send out any queries.
• VLAN Operational Max Response Time: Indicates the time to wait before removing a Leave from a host upon receiving a Leave request. This value is calculated dynamically from the Queries received from the network. If the Snooping Switch is in Querier state, then it is equal to the configured value.
• Querier Election Participate: Indicates whether the MLD Snooping Querier participates in querier election if it discovers the presence of a querier in the VLAN.
• Querier VLAN Address: The IP address will be used in the IPv6 header while sending out MLD queries on this VLAN. It can be configured using the appropriate command.
• Operational Version: This version of IPv6 will be used while sending out MLD queriers on this VLAN.
• Last Querier Address: Indicates the IP address of the most recent Querier from which a Query was received.
• Last Querier Version: Indicates the MLD version of the most recent Querier from which a Query was received on this VLAN.

When the optional argument detail is used, the command shows the global information and the information for all Querier-enabled VLANs.