Reverse DNS Records

What Are Reverse DNS Records?

Reverse DNS (rDNS) records, also known as PTR (Pointer) records, work opposite to standard DNS. While standard DNS maps a domain name to an IP address, reverse DNS maps an IP address back to a domain name.

How Reverse DNS Works

When a standard DNS lookup is performed:

Forward DNS: example.com → 192.168.1.1
Reverse DNS: 192.168.1.1 → example.com

Reverse DNS uses a special domain called in-addr.arpa for IPv4 addresses and ip6.arpa for IPv6 addresses. The IP address is reversed and appended to the appropriate arpa domain.

For example, the PTR record for 192.168.1.1 would be looked up as: 1.1.168.192.in-addr.arpa

Why Reverse DNS Matters

Email deliverability: Many mail servers check reverse DNS to verify the sending server’s identity. If rDNS is not set up, your emails may be marked as spam or rejected entirely.
Network troubleshooting: Tools like traceroute use rDNS to display hostnames along the network path.
Security and logging: rDNS helps identify the source of network connections in server logs.
Compliance: Some services and security policies require valid rDNS records.

Who Can Set Up Reverse DNS?

PTR records are controlled by the owner of the IP address, not the domain owner. This means:

Your hosting provider or ISP is responsible for setting up reverse DNS for your IP addresses.
Domain registrars typically cannot set PTR records because they do not own the IP address blocks.
PTR records are generally only available on VPS hosting or dedicated servers. Shared hosting environments usually don’t allow individual PTR records because it would affect all users on the server.

How to Set Up Reverse DNS

Contact your hosting provider or server administrator.
Request that they create a PTR record for your server’s IP address.
Provide them with the desired hostname (e.g., mail.example.com).
Ensure the forward DNS (A record) also matches — the hostname should resolve to the same IP address.

Checking Reverse DNS

You can verify reverse DNS using these methods:

Command Line

# On Windows
nslookup 192.168.1.1

# On Mac/Linux
dig -x 192.168.1.1
host 192.168.1.1