Add a DNS delegation to IPv6 and IPv4

You can't edit the reverse of IPv4 /27 blocks & the IPv6 blocks (/48 - /56 - /64) directly in the console.
Therefore you'll have to delegate your subnet to your nameservers.

It will delegate the task to propagate DNS reverses of your IPs on the Internet to your servers.
You will need two DNS servers for redundancy.

You can delegate the subnets directly in your account.

At first you'll have to go to the network configuration in your account: “Server” > “Network configuration”:

You'll have to click then on the cogwheel next to your IP block. Click on “Edit nameserver delegation” then:

You'll have to repeat this for all your /27 IPv4 blocks.
For IPv6 it will be enough to delegate your /48 as all subnets in your block will automatically configured to the same nameservers.

Here is an example BIND configuration for the block 62.4.10.0/27:

0-27.10.4.62.in-addr.arpa.     86400   IN      SOA     ns1.mydns.net. hostmaster.mydns.net. (
                                      2013121407     ; Serial
                                      10800   ; Refresh
                                      1800    ; Retry
                                      604800  ; Expire
                                      86400 ) ; Minimum TTL
0-27.10.4.62.in-addr.arpa.     86400   IN      NS      ns1.mydns.net.
0-27.10.4.62.in-addr.arpa.     86400   IN      NS      ns2.mydns.net.
1.0-27.10.4.62.in-addr.arpa.   86400   IN      PTR     toto.domaine.com.

The line SOA indicates the authoritative server for the IP block,

The lines NS indicates the propagating DNS servers for the concerned IP block.

The lines PTR indicates the revers of the indicated IP, here 62.4.10.1.

The configuration of IPv6 is done in the same way.
You have to create a reverse zone directly on your DNS server.

Here a BIND example for the zone 2001:bc8::3398::/48:

;
; 2001:bc8:3398::/48
;
; Zone file built with the IPv6 Reverse DNS zone builder
; http://rdns6.com/
;
$TTL 1h ; Default TTL
8.9.3.3.8.c.b.0.1.0.0.2.ip6.arpa.       IN      SOA     ns1.domain.fr  webmaster.domain.fr (
        2016071503      ; serial
        1h              ; slave refresh interval
        15m             ; slave retry interval
        1w              ; slave copy expire time
        1h              ; NXDOMAIN cache time
        )

;
; domain name servers
;
@       IN      NS      ns1.domain.fr.
@       IN      NS      ns2.domain.fr.


; IPv6 PTR entries
1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.9.3.3.8.c.b.0.1.0.0.2.ip6.arpa.    IN    PTR    toto.domain.fr.

In case of need, you can use the utilities available at rdns6.com to facilitate the generation of your zones.