4.1. Routing

4.1. Routing

Local IPv6 addresses are designed to be routed inside of a site in the same manner as other types of unicast addresses. They can be carried in any IPv6 routing protocol without any change.

It is expected that they would share the same Subnet IDs with provider-based global unicast addresses, if they were being used concurrently [GLOBAL].

The default behavior of exterior routing protocol sessions between administrative routing regions must be to ignore receipt of and not advertise prefixes in the FC00::/7 block. A network operator may specifically configure prefixes longer than FC00::/7 for inter-site communication.

If BGP is being used at the site border with an ISP, the default BGP configuration must filter out any Local IPv6 address prefixes, both incoming and outgoing. It must be set both to keep any Local IPv6 address prefixes from being advertised outside of the site as well as to keep these prefixes from being learned from another site. The exception to this is if there are specific /48 or longer routes created for one or more Local IPv6 prefixes.

For link-state IGPs, it is suggested that a site utilizing IPv6 local address prefixes be contained within one IGP domain or area. By containing an IPv6 local address prefix to a single link-state area or domain, the distribution of prefixes can be controlled.