# Specifying Multicast Groups

You can use a standard IPv6 access list to specify the multicast groups that a host can join.

ipv6 mld access-group

- Use to restrict hosts on this subnetwork to join only multicast groups that appear on the specified IPv6 access list.
- When configured, the access list is queried whenever the router receives an MLDv1 report requesting membership of a group and MLDv2 ChangeToInclude, IsInclude, ChangeToExclude, or IsExclude reports. The request is ignored if the access list query fails. The ipv6 mld access-group command uses IPv6 access lists, which allow both source and destination/group addresses to be specified. You must set the source address to “ any.”
- Use the MLD-Access-Name RADIUS attribute (VSA 26-74) in RADIUS Access-Accept messages as an alternative method of configuring this value.
- Example
  host1:boston(config-if)#ipv6 mld access-group boston-list
- Use the no version to dissociate the interface from an access list and to allow hosts on the interface to join any multicast group.
- See ipv6 mld access-group.

ipv6 mld access-source-group

- Use to restrict hosts on this subnetwork to membership in those (S,G) pairs (also known as “ channels” ) permitted by the specified IPv6 access list.
- When configured, both source and group addresses query the associated access list whenever the router receives an MLDv2 report requesting membership of the (S,G) pairs (that is, the router receives an MLDv2 ChangeToInclude, IsInclude, or AllowNewSource group report). The request is ignored if the access list query fails. The ipv6 mld access-source-group command uses IPv6 access lists, which allow both source and destination group addresses to be specified.
- Use the MLD-Access-Src-Name RADIUS attribute (VSA 26-75) in RADIUS Access-Accept messages as an alternative method of configuring this value.
- Example
  host1:boston(config-if)#ipv6 mld access-source-group dallas-list
- Use the no version to remove any access list restriction.
- See ipv6 mld access-source-group.