Domain Name System (DNS) is a mechanism which allows searching for a domain name by its IP address and visa versa, as well as other information that resource records contain. For more information please refer to the article Domain resource record.
Accordance of IP address and reverse domain name
A PTR record of the reverse domain zone is used to define a domain name by IP address. Some Internet services require that IP addresses must be converted into names. To execute a request, a node address is converted to reverse; them conversion method depends on IP version.
IPv4
An IPv4 address consists of four octets of the address expressed individually in decimal numbers from 0 to255, separated by periods, e.g. 192.168.0.1. "in-addr.arpa." domain is used to search for domain names by Ipv4-addresses. An IP-address is specified in the domain name in the reverse order. E.g. 195.161.72.28 corresponds to the domain name "28.72.161.195.in-addr.arpa.".
IPv6
IPv6 address is represented as eight groups of four hexadecimal digits, each group representing 16 bits (two octets) from 0 to ffff, separated by colons, e.g., 3107:0c38:0a67:0000:0000:e446:3925:0091. "ip6.arpa." domain is used to search domain names by Ipv6-addresses. An IP-address is specified in the domain name in the reverse order. E.g., 3107:0c38:0a67:0000:0000:e446:3925:0091 corresponds to the domain name "1.9.0.0.5.2.9.3.6.4.4.e.0.0.0.0.0.0.0.0.7.6.a.0.8.3.c.0.7.0.1.3.ip6.arpa.".
Reverse domain zones
IPv4
IPmanager can work with prefixes /8, /16, /24 for IPv4 networks. When you create a network with /23, two reverse domain zones will be created with /24. Accrodingly, when you create a network with /14, four domain zones with /16 will be created. When you create a network with the mask lower than /24, the system will create either a network with /24, or classless reverse domain zone with the mask prefix equal to the prefix of the network you create.
IPv6
IPmanager can work with prefixes /12, /16, /20, /24, /28, /32, /48, /64 for IPv6 networks. When you create a network with /47, two reverse domain zones will be created with /48. Accordingly, when you create a network with /49, 32768 domain zones with /64 will be created. When you create a network with the mask lower than /64, the system will create either a network with /64 or classless reverse domain zone with the mask prefix equal to the prefix of the network you create.