Domain Name System
IPv6 Addresses in DNS

IPv6 addresses are stored into DNS in the same way as in IPv4. The client uses the following types of queries to communicate with DNS server:

Standard DNS Queries

A new AAAA record type was introduced for DNS queries. The name of the new record type is derived from the length of an IPv6 address, which is four times larger in comparison with the length of an IPv4 address. In the case of IPv4, the DNS query uses A record type.

If host.cvut.cz computer has the address 2001:718:8DE:128:3201:A1FF:FE67:12, the following entry will be included in a zone file for cvut.cz domain:

Entry

Then the zone file of cvut.cz domain in which there is an authoritative name server and a computer, it may look like this:

Zone File

When a network uses multiple prefixes, computers typically have multiple IPv6 addresses. Then, each IPv6 address must have a corresponding AAAA record in a zone file in DNS server.

Inverse DNS Queries

Inverse DNS query is used to obtain the domain name to well-known IPv6 address. PTR records are used as in the case of IPv4. Inverse DNS query is formed by the inverse sequence of hexadecimal digits of IPv6 address to whose end the ip6.arpa domain is connected. IPv6 address must be complete. It means that it must contain all zeros. Inverse DNS query for above mentioned address 2001:718:8DE:128:3201:A1FF:FE67:12 has the form:

Inverse DNS Query

The prefix will be at the end of inverse DNS query due to an inverse sequence of digits, which allows implementing distributed management of inverse domains.

If the CTU network has the prefix 2001:718:8DE::/48, the DNS server of CTU will manage E.D.8.0.8.1.7.0.1.0.0.2.ip6.arpa inverse domain. The following entry will be included in a zone file for this inverse domain:

Entry for Inverse Domain

Then the zone file of inverse domain that corresponds to cvut.cz domain may look like this:

Zone File of Inverse Domain