IPv4 Reverse DNS Name Generator
Generate address-level reverse lookup names.
IPv4 Reverse DNS Name Generator: inputs and results
Enter an IP address, CIDR prefix, or range. Then check its first and last address below.
Calculated Boundaries & ParametersReady
Key Capabilities
- •100% Client-Side: Zero telemetry or server latency.
- •RFC Compliant: Exact 32-bit and 128-bit integer precision.
- •Quick Copy: Instant access to CIDR, mask, and range bounds.
- •Cross-Platform: Works on desktop, tablet, and mobile browsers.
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How IPv4 Reverse DNS Name Generator Works?
This tool works by reversing the 4 octets of the address and appending in-addr.arpa, the domain used for IPv4 PTR lookups.
Enter an IPv4 address
Type an address such as
198.51.100.25.Reverse the octets
The order 198, 51, 100, 25 becomes 25, 100, 51, 198.
Append the suffix
The generator adds
.in-addr.arpa:25.100.51.198.in-addr.arpa.Show the zone names
The generator prints the /24, /16, and /8 zones that hold the record next to the PTR name.
IPv4 Reverse DNS Name Generator Formula
The formula is PTR Name = o₄.o₃.o₂.o₁.in-addr.arpa.
PTR name
o4.o3.o2.o1.in-addr.arpaOctets in reverse order.
/24 zone
o3.o2.o1.in-addr.arpaHolds 256 PTR records.
/16 zone
o2.o1.in-addr.arpaHolds 65,536 PTR records.
Record label in /24 zone
o4The host part inside the zone file.
Worked example: 198.51.100.25
PTR name = 25.100.51.198.in-addr.arpa /24 zone = 100.51.198.in-addr.arpa Zone record: 25 IN PTR mail.example.com.
IPv4 Reverse DNS Name Generator Conversion Table
The table shows the PTR name and /24 zone for 10 IPv4 addresses.
| IPv4 Address | PTR Name | /24 Reverse Zone |
|---|---|---|
| 8.8.8.8 | 8.8.8.8.in-addr.arpa | 8.8.8.in-addr.arpa |
| 1.1.1.1 | 1.1.1.1.in-addr.arpa | 1.1.1.in-addr.arpa |
| 10.0.0.1 | 1.0.0.10.in-addr.arpa | 0.0.10.in-addr.arpa |
| 127.0.0.1 | 1.0.0.127.in-addr.arpa | 0.0.127.in-addr.arpa |
| 172.16.5.20 | 20.5.16.172.in-addr.arpa | 5.16.172.in-addr.arpa |
| 192.0.2.10 | 10.2.0.192.in-addr.arpa | 2.0.192.in-addr.arpa |
| 192.168.1.254 | 254.1.168.192.in-addr.arpa | 1.168.192.in-addr.arpa |
| 198.51.100.25 | 25.100.51.198.in-addr.arpa | 100.51.198.in-addr.arpa |
| 203.0.113.200 | 200.113.0.203.in-addr.arpa | 113.0.203.in-addr.arpa |
| 100.64.10.5 | 5.10.64.100.in-addr.arpa | 10.64.100.in-addr.arpa |
What is IPv4 Reverse DNS Name Generator?
The IPv4 Reverse DNS Name Generator is a tool that builds the in-addr.arpa domain name used to look up the hostname of an IPv4 address.
Forward DNS maps names to addresses. Reverse DNS maps addresses back to names through PTR records stored under in-addr.arpa, defined in RFC 1035. The octets are reversed, since DNS names read from the most specific label on the left to the least specific on the right.
Email servers, SSH servers, and log tools all use reverse lookups. Many mail receivers reject or flag messages from IPv4 hosts with no PTR record or with a PTR that does not match the forward name.
What are the uses of IPv4 Reverse DNS Name Generator?
There are 4 main uses of the IPv4 Reverse DNS Name Generator, including PTR record creation, mail server setup, and troubleshooting.
Creating PTR records
Zone files and DNS dashboards need the reversed name for each record.
Setting up mail servers
Hosting providers ask for the PTR name when configuring reverse DNS for a mail IP.
Running manual lookups
The name works in
dig PTR 25.100.51.198.in-addr.arpa.Requesting zone delegation
ISPs delegate /24 reverse zones by their in-addr.arpa name.