DHCPv6 Option 56 configuration

[Marek Hajduczenia]

Dear mailing list users,
I have been trying to define NTPv6 option to use with ISC-DHCPD6 daemon
(4.4.1 running on Ubuntu 22.04 server) as follows

# ntp option 56
option space ntp code width 2 length width 2 hash size 2;
option ntp.address code 1 = array of ip6-address;
option opt56 code 56 = encapsulate ntp;

and then use it in a subnet as follows

shared-network enp7s0 {
    authoritative;
    # deny bootp;
    subnet6 fc00:6ce4:40:146::/64 {
        pool6 {
            # vendor-option-space ntp;
            option ntp.address fc00:6ce4:40:146::1;
            default-lease-time 600;
            min-lease-time 450;
            max-lease-time 900;
            allow all clients;
            range6 fc00:6ce4:40:146::10 fc00:6ce4:40:146::ffff;
        }
    }
}

but no matter what I do, the ISC does not seem to include Option 56 in the
Reply / Advertise messages, even though the client does request Option 56.
I have spent probably 48 hrs in total already, resulting in discovering
that the only thing that seems to be working is a brute force hex encoded
string (example below)

option dhcp6.ntp-servers code 56 = string;
option dhcp6.ntp-servers
00:01:00:10:20:01:0d:b8:0c:a2:00:02:00:00:00:00:00:00:00:01;

Is there any trick to forcing the ISC daemon to include the encapsulation
option?

Thank you in advance

M
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