#send dhcp-client-identifier 1:0:a0:24:ab:fb:9c;
#send dhcp-lease-time 3600;
#supersede domain-name “fugue.com home.vix.com”;
prepend domain-name-servers :  You put the ip address of the DNS servers you want nslookup to use ; separates them
#require subnet-mask, domain-name-servers;
timeout 300;
#retry 60;
#reboot 10;
#select-timeout 5;
#initial-interval 2;
#script “/sbin/dhclient-script”;
#media “-link0 -link1 -link2”, “link0 link1”;

When you install isc-dhcp-server, you need to copy the config files as isc-dhcp-server6 in each area. 


# DHCPDv4_CONF=/etc/dhcp/dhcpd.conf
# DHCPDv6_CONF=/etc/dhcp/dhcpd6.conf

# Path to dhcpd’s PID file (default: /var/run/dhcpd.pid).
# DHCPDv4_PID=/var/run/dhcpd.pid

# Additional options to start dhcpd with.
# Don’t use options -cf or -pf here; use DHCPD_CONF/ DHCPD_PID instead

I added a DHCP server to my primary DNS server.  I enabled IPv4 and IPv6.

Setting up host addresses for IPv6 is tricky.

host ubuntu Server_Name {
host-identifier option dhcp6.client-id Long_ID_String;
fixed-address6 IPv6 address;

How to get

host-identifier option dhcp6.client-id?
I opened the DHCPv6 server. 

sudo systemctl -l isc-dhcp-server6

Go the the server that you want to find the information on

sudo netplan try, enter, sudo netplan apply

Load sudo systemctl -l isc-dhcp-server6 again.  You will see it on the screen.  Copy the string into /etc/dhcp/dhcp6.conf for that server.

Sudo systemctl restart isc-dhcp-server6 or sudo reboot.  do try and apply again and ifconfig to check