It was rather easy to get IPv6 working with DA if you have the IPv6 subnet allocated for your server.
Make sure that you have IPv6 enabled on your DA.
# grep ipv6 /usr/local/directadmin/conf/directadmin.conf
Add the IPv6 Addresses to your direct admin, through IP Management (This will add IPv6 address to the interface).
Enter the IPv6 Address in IP field and keep the Netmask as 255.255.255.0
Add IPv6 address for your name servers,
go to DNS administration –> Select your name server domain –> Add AAAA records for your Name Servers. Make sure you have added the IPv6 addresses already to DA.
Check your name server is resolving/reachable via IPv6.
Now to add IPv6 Address to hosted domains, select the domain –> Modify user –> select the IPv6 address in “Add Additional IP”. If the IPv6 address is not visible, make sure it is added to DA and to the reseller account you are editing the domain.
Add the IPv6 address(AAAA) to the corresponding domains DNS configuration.
Here we go, ping666666