Configuring IPv6 address blocks
Configuring reverse resolution initially requires configuring a DNS server for a specific domain.
In the case of a /64 IPv6 block, for example, 2001:0DB8::, a domain name must be configured for: 0.0.0.0.0.0.0.0.8.B.D.0.1.0.0.2.ip6.arpa.
In a DNS server running BIND software in a Unix environment, this configuration would require the steps detailed below.
Creation of a general configuration file containing the following lines (in addition to any other lines of code needed for the proper operation of the server):
These lines specify the zone for which this is the authoritative server, the type of server (master or slave) and the name of the file where the information about the zone will be stored.
The next step is to create a file to contain the information about the zone. The name of this file must be the same name specified in the server's general configuration.
Basically, this file will contain the following information:
0.0.0.0.0.0.0.0.8.B.D.0.1.0.0.2.ip6.arpa. IN SOA ns.example.org root.example.org (
1 ; serial
3600 ; refresh
3600 ; retry
3600 ; expire
900) ; minimum
0.0.0.0.0.0.0.0.8.B.D.0.1.0.0.2.ip6.arpa. IN NS ns.example.org.
220.127.116.11.0.0.0.0.0.0.0.0.0.0.0.0 IN PTR host1.example.org.
18.104.22.168.0.0.0.0.0.0.0.0.0.0.0.0 IN PTR host2.example.org.
The lines above specify the name of the zone that is being configured and its Resource Records (RR), for example, the Start of Authority (SOA), which specifies the authoritative server for this zone.
The information between brackets is used to organize the synchronization of secondary servers (slaves). This is followed by information on the DNS servers for the zone, which may be more than one.
Finally, the file includes the most interesting information from the point of view of reverse resolution, i.e., the name associated with each IP address in the block.
Resource Record PTR specifies a pointer between the address and the corresponding name. For example, the IP address 2001:0DB8:0000:0000:0000:0000:0000:0001 (which can also be represented as 2001:0DB8::1) is associated with the name host1.example.org.