5. Address Types

Since Link-local unicast addresses are defined for use on a single link only, those may be used on the PE-CE link, but they are not supported for reachability across IPv6 VPN Sites and are never advertised via MultiProtocol-Border Gateway Protocol (MP-BGP) to remote PEs.

Global unicast addresses are defined as uniquely identifying interfaces anywhere in the IPv6 Internet. Global addresses are expected to be commonly used within and across IPv6 VPN Sites. They are obviously supported by this IPv6 VPN solution for reachability across IPv6 VPN Sites and advertised via MP-BGP to remote PEs and are processed without any specific considerations to their global scope.

Quoting from [UNIQUE-LOCAL]: "This document defines an IPv6 unicast address format that is globally unique and is intended for local communications [IPv6]. These addresses are called Unique Local IPv6 Unicast Addresses and are abbreviated in this document as Local IPv6 addresses. They are not expected to be routable on the global Internet. They are routable inside of a more limited area such as a site. They may also be routed between a limited set of sites."

• [UNIQUE-LOCAL] also says in its Section 4.7: "Local IPv6 addresses can be used for inter-site Virtual Private Networks (VPN) if appropriate routes are set up. Because the addresses are unique these VPNs will work reliably and without the need for translation. They have the additional property that they will continue to work if the individual sites are renumbered or merged."

In accordance with this, Unique Local IPv6 Unicast Addresses are supported by the IPv6 VPN solution specified in this document for reachability across IPv6 VPN Sites. Hence, reachability to such Unique Local IPv6 Addresses may be advertised via MP-BGP to remote PEs and processed by PEs in the same way as Global Unicast addresses.

Recommendations and considerations for which of these supported address types should be used in given IPv6 VPN environments are beyond the scope of this document.