Master/Slave Reverse Zones
Master Reverse Zone
While in the Master zone your hostname is pointed to an IP address, using the Master Reverse zone allows you to point an IP address to a hostname.
How to add it?
If your IP is 126.96.36.199., you need to reverse it to 188.8.131.52.
After the zone is created you will be able to add the PTR record(s) pointed to your domain(s).
When you create the Master Reverse zone, you need to ask the IP owner to delegate the management of the IP to our servers.
Slave Reverse Zone
For creating Slave Reverse Zone (Secondary DNS for Reverse DNS zones), you need to Login in your account, click on the DNS zones [Add new] link, click on the Slave reverse zone box, write the reverse zone name as is showed above, enter the Master server IP and click on "Register".
The IPv6 zone needs to be in the format 184.108.40.206.220.127.116.11.18.104.22.168.22.214.171.124.126.96.36.199.188.8.131.52.184.108.40.206.220.127.116.11 for IPv6 2109:8765:4321:0987:6543:2109:8765:4321 and from the drop-down menu needs to be chosen ip6.arpa.
The master IP can be either IPv6 or IPv4, no matter what is the type of the zone.