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4.6. Use of Local IPv6 Addresses for Local Communication

4.6. Use of Local IPv6 Addresses for Local Communication​

Local IPv6 addresses, like global scope unicast addresses, are only assigned to nodes if their use has been enabled (via IPv6 address autoconfiguration [ADDAUTO], DHCPv6 [DHCP6], or manually). They are not created automatically in the way that IPv6 link-local addresses are and will not appear or be used unless they are purposely configured.

In order for hosts to autoconfigure Local IPv6 addresses, routers have to be configured to advertise Local IPv6 /64 prefixes in router advertisements, or a DHCPv6 server must have been configured to assign them. In order for a node to learn the Local IPv6 address of another node, the Local IPv6 address must have been installed in a naming system (e.g., DNS, proprietary naming system, etc.) For these reasons, controlling their usage in a site is straightforward.

To limit the use of Local IPv6 addresses the following guidelines apply:

  • Nodes that are to only be reachable inside of a site: The local DNS should be configured to only include the Local IPv6 addresses of these nodes. Nodes with only Local IPv6 addresses must not be installed in the global DNS.

  • Nodes that are to be limited to only communicate with other nodes in the site: These nodes should be set to only autoconfigure Local IPv6 addresses via [ADDAUTO] or to only receive Local IPv6 addresses via [DHCP6]. Note: For the case where both global and Local IPv6 prefixes are being advertised on a subnet, this will require a switch in the devices to only autoconfigure Local IPv6 addresses.

  • Nodes that are to be reachable from inside of the site and from outside of the site: The DNS should be configured to include the global addresses of these nodes. The local DNS may be configured to also include the Local IPv6 addresses of these nodes.

  • Nodes that can communicate with other nodes inside of the site and outside of the site: These nodes should autoconfigure global addresses via [ADDAUTO] or receive global address via [DHCP6]. They may also obtain Local IPv6 addresses via the same mechanisms.

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