pfSense

There are currently four types of DUID (DHCP Unique Identifier) defined in IETF RFCs - DUID-LLT, DUID-EN, and DUID-LL (types 1, 2, and 3, cf. https://tools.ietf.org/html/rfc3315#section-9.1) and DUID-UUID (type 4, cf. https://tools.ietf.org/html/rfc6355) - and more may be defined in the future.

Since https://redmine.pfsense.org/issues/3971 was resolved, pfSense allows configuring a DUID-LLT in webConfigurator under System->Advanced->Networking. Whatever the user inputs there is written to dhcp6c's DUID file at /var/db/dhcp6c_duid. Although dhcp6c will only create a DUID-LLT on its own, it stores the entirety of the OPTION_CLIENTID option in the DHCPv6 datagrams it sends in its DUID file, except for the DHCPv6 option code of OPTION_CLIENTID itself. Therefore, by writing a correctly formed DUID file, the current DUID-LLT configuration facility in pfSense could be extended to allow configuring all current and future DUID types.

Sorry about Post 1, I typo'd the type numbers. Post 2 is correct.

The different DUID types also appear to be formatted and stored in config.xml correctly for each respective option.

(On latest CE master.)