pfSense

Please implement RFC8781 Discovering PREF64 in Router Advertisements (IPv6-Mostly Networks) to support IPv6-Mostly Networks

- This is implemented in radvd v2.20_rc1 https://github.com/radvd-project/radvd/blob/master/CHANGES
- radvd needs to be upgraded and a option to configure this in the UI

https://datatracker.ietf.org/doc/html/rfc8781
https://www.ietf.org/archive/id/draft-link-v6ops-6mops-01.html

In a nutshell, an IPv6-mostly network is very much similar to a dual-stack one with two additional key elements:

• The network provides NAT64 ([RFC6146] ) functionality ([RFC6146]), enabling IPv6-only clients to communicate with IPv4-only destinations.
• The DHCPv4 infrastructure processing DHCPv4 Option 108 as per [RFC8925].

Upon connecting to an IPv6-mostly network segment, an endpoint configures its IP stack based on its capabilities:

• IPv4-Only Endpoint: Acquires an IPv4 address through DHCPv4.
• Dual-Stack Endpoint (Not IPv6-Only Capable): Configures IPv6 addresses via Stateless Address Autoconfiguration (SLAAC) and, optionally, DHCPv6. Additionally, it obtains an IPv4 address via DHCPv4 or by other means.
• IPv6-only capable endpoint configures its IPv6 addresses and, while performing DHCPv4, includes option 108 ([RFC8925] ) into the Parameter Request List. The DHCP server returns the option and, as per [RFC8925] , the endpoint forgoes requesting an IPv4 address, remaining in IPv6-only mode.

An IPv6-mostly network segment can support a mix of IPv4-only, dual-stack, and IPv6-only devices. IPv6-only endpoints utilize the network-provided NAT64 along with DNS64 services to reach IPv4-only destinations.

NAT64 can be done externally, but PREF64 and DHCPv4 option 108 has to be in pfSense.