Configuring MLD Options for Default and Non-Default VRFs

Multicast Listener Discovery Version 2 (MLDv2) allows you to configure options on default and non-default virtual routing instances (VRFs).

The default MLD version when IPv6 PIM Sparse Mode (PIM-SM) is enabled on an interface is MLDv1. You must configure MLDv2 on an interface to enable MLDv2.

The following option configurations are outlined in the steps below:

  • Modify the group membership time—Group membership time defines how long a group will remain active on an interface in the absence of a group report. Values range from 5 through 26000 seconds; the default is 260.
  • Modify the MLD query interval—Frequency at which multicast listening discovery (MLD) query messages are sent. Values range from 2 through 3600 seconds; the default is 125. The MLD query interval value you enter must be greater than the interval configured by the maximum response time.
  • Last Listener Query Interval—the maximum response delay inserted into Multicast-Address-Specific Queries sent in response to done messages, and is also the amount of time between Multicast-Address-Specific Query messages. When the device receives an MLDv1 leave message or an MLDv2 state change report, it sends out a query and expects a response within the time specified by this value.
  • Modify the maximum response time—The maximum amount of time a multicast listener has to respond to queries. Values range from 1 through 25; the default is 10.
  • Modify the maximum number of MLD group addresses—Any MLD group memberships exceeding the group limit are not processed. Values range from 1 through 8192; the default is 4096.
  • Robustness—The number of times that the switch sends each MLD message from an interface. Use a higher value to ensure high reliability from MLD. Values range from 2 through 7; the default is 2.

The following task steps can be configured in any order and are all optional. The steps show how to configure these options for a specific VRF named blue. You can enable IPv6 PIM using the ipv6 router pim command without specifying a VRF to make these options apply to the default VRF.

  1. Enter global configuration mode.
    device# configure terminal
  2. Enable IPv6 PIM SM for a VRF named blue.
    device(config)# ipv6 router pim vrf blue
  3. Modify the group membership time to 2000 seconds.
    (config-ipv6-pim-router-vrf-blue)# ipv6 mld group-membership-time 2000
    When multiple devices are connected together, all devices must have the same group membership time configured, which must be at least twice the length of the query interval, so that missing one report does not stop traffic.
  4. Modify the frequency at which MLD query messages are sent for a specified VRF, in seconds.
    device(config-ipv6-pim-router-vrf-blue)# ipv6 mld query-interval 50
  5. Modify the last listener query interval sent for a specified VRF, in seconds.
    device(config-ipv6-pim-router-vrf-blue)# ipv6 mld llqi 5
    The range of values is from 1 through 25; the default is 1.Using a lower value allows members to leave groups more quickly.
  6. Modify the IGMP maximum response time, in seconds.
    device(config-ipv6-pim-router-vrf-blue)# ipv6 mld max-response-time 5
  7. Modify the maximum number of MLD group addresses.
    device(config-ipv6-pim-router-vrf-blue)# ipv6 mld max-group-address 1000
  8. Modify the MLD robustness for a specified VRF.
    device(config-ipv6-pim-router-vrf-blue)# ipv6 mld robustness 3

The following example configures various MLD options for the VRF named blue.

device# configure terminal
device(config)# ipv6 router pim vrf blue
(config-ipv6-pim-router-vrf-blue)# ipv6 mld group-membership-time 2000
device(config-ipv6-pim-router-vrf-blue)# ipv6 mld query-interval 50
device(config-ipv6-pim-router-vrf-blue)# ipv6 mld llqi 5
device(config-ipv6-pim-router-vrf-blue)# ipv6 mld max-response-time 5
device(config-ipv6-pim-router-vrf-blue)# ipv6 mld max-group-address 1000
device(config-ipv6-pim-router-vrf-blue)# ipv6 mld robustness 3