Reverse DNS delegation

Reverse DNS is the process of using the DNS (Domain Name System) to translate IP addresses to hostnames. Reverse DNS is the opposite of forward DNS, which is used to translate human readable hostnames to IP addresses.

DNS queries start from the 'root' in the DNS tree. In the case of reverse DNS, the query travels from the root to the DNS server of the Regional Internet Registry (RIR), which contains the authoritative information for the RIR-delegated IP block, for example, 202/8: 202.in-addr.arpa.

The APNIC DNS server is able to give the referral if it has the DNS Name Server (NS) information of the network or end party who received the IP delegation from APNIC. This is what we call reverse DNS delegation.

For all IP addresses the Internet Assigned Numbers Authority (IANA) allocates to APNIC, IANA also delegates corresponding reverse DNS zones within the centrally administered in-addr.arpa and ip6.arpa domains.

APNIC manages reverse DNS for both IPv4 and IPv6

Reverse delegations for IPv4 are based on octet boundaries, or a /8, /16, and /24 reverse zones. For example, if you have been delegated a /22 IPv4 block from APNIC, you need to register four /24 reverse zones.

Reverse delegations for IPv6 are based on the closest 4-bit boundaries. The default prefix size for IPv6 delegations made are a /32 and /48. For example, if you have been delegated a /32 IPv6 block from APNIC, you should register a /32 reverse zone.

If your customers have their own reverse DNS servers, you need to manage their reverse delegations from within your DNS name servers by adding NS records for the reverse zones you delegate to your customers.

How to register reverse delegations with APNIC

You can register your reverse delegation using MyAPNIC, through the "Resources" tab:

Resources > Whois updates > Add > Object Type: domain

The domain object form will allow you to register your domain object in the Whois Database. You will need to provide your IP prefix, name(s) of your DNS Name Server(s), and your Maintainer object name in the form.

After your domain object is registered, the reverse delegation will become visible on Name Servers in the following order:

1. APNIC Name Server

Reverse zones are generated from the APNIC Whois Database every two hours. Cached zones at ns.apnic.net are refreshed with new and updated reverse zones every two hours.

2. Global Name Servers

After ns.apnic.net reloads its configuration and zone files, it will take additional time (depending on the TTL and refresh values) to update the worldwide DNS servers.

More about managing reverse DNS

Before you register your domain objects, you need to ensure that your reverse zones have been configured and loaded in your DNS name servers. Creating a reverse zone is the same as creating any other zone file. The Start of Authority (SOA) and initial Name Server (NS) records are the same as any normal zone. However, you will need to create additional PTR records.

APNIC does not host your DNS name servers or configure your reverse zone files. APNIC only delegates the authority of your reverse zones to the DNS name servers you provide through your domain objects. If you do not have a DNS service, you may need to contact your ISP, hosting provider, or third party DNS provider to configure your reverse zones and load them in their DNS name servers. You can then register your domain objects using those DNS name servers.

Manage Reverse DNS

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