How to set up Reverse DNS
TL;DR
- Reverse DNS (rDNS) maps an IP address back to a domain name using a PTR record.
- rDNS is separate from normal DNS and must be configured on the authoritative nameserver for the IP address.
- Setting up rDNS involves creating a reverse DNS zone and adding the correct PTR record.
- Proper reverse DNS improves email deliverability, server reputation, and overall trust.
- Many hosting providers (like HOSTAFRICA) can assign rDNS for you on request.
Table of Contents
As the name implies, Reverse DNS is the inverse of normal (forward) DNS. DNS (Domain Name Service) translates a human-readable URL or domain name into an IP address for the computer to read. Reverse DNS is useful when you have an IP address and need to find the domain name. A Reverse DNS query will offer a Reverse Pointer or PTR record. Although Reverse DNS seems straightforward, it can be tricky to set up. Despite performing the reverse function of standard DNS, the two are completely different and separate lookups. Find out what is a parked domain.
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How to set up Reverse DNS
Step 1: Create a Reverse DNS zone
It is very important that you create the reverse DNS zone on the authoritative DNS nameserver for the main IP address of your server. If the Reverse response is not already provided by your nameserver, you can contact your hosting provider to set up a PTR record. If you control the authoritative nameserver, you can go ahead with creating a reverse DNS zone. The format for the zone hostname must be very specific, starting with a fragment of your IP address written in reverse followed by .in-addr.arpa. For example:
- If your IP address is 168.0.100, drop the last set of numbers to make 192.168.0
- Reverse the IP fragment to make 168.192
- Add .in-addr.arpa. to get the complete reverse zone domain of 168.192.in-addr.arpa.
Step 2: Create the PTR record
You’ve created your zone file; now you can create the PTR record. First, add a new PTR record and enter the final octet of the IP address that you’re setting up the reverse record for as the name of the record. This will be the set of numbers that you removed in Step 1. In our example, the name will be 100. Then, enter the domain name you want the IP address to resolve to for the Canonical Hostname. For example, mailserver.example.com. Lastly, save your zone file and allow time for the change to take effect.
Step 3: Validate your reverse DNS record
You can validate the new reverse DNS record by running the DIG Web Interface Tool. If the setup is a success, you should get a lookup answer that looks similar to this: 100.0.168.192.in-addr.arpa. 6230 IN PTR mailserver.example.com
Frequently Asked Questions (FAQ)
What is Reverse DNS used for?
Reverse DNS is mainly used for email servers, logging, and security checks. It helps confirm that an IP address is legitimately associated with a domain, which is especially important for spam prevention.
Is Reverse DNS required for email delivery?
While not strictly required, most mail servers expect rDNS to be configured. Missing or incorrect rDNS can cause emails to be flagged as spam or rejected entirely.
Can I set up Reverse DNS myself?
You can only set up rDNS if you control the authoritative DNS for the IP address. In most cases, this means asking your hosting provider to create or update the PTR record for you.
How long does Reverse DNS take to propagate?
Reverse DNS changes usually propagate within a few minutes to several hours, but in some cases it can take up to 24 hours, depending on DNS caching and TTL values.
Speak to HOSTAFRICA for DNS advice
Having Reverse DNS set up shows that you care about your internet reputation. Reverse DNS will start becoming even more important with the implementation of IPV6. At HOSTAFRICA, we can assign your Reverse DNS on request and ensure that both your Reverse and Forward DNS match. Contact HOSTAFRICA today for assistance with Reverse DNS setup.
Learn More About DNS Setup
Reverse DNS is useful for improving trust, deliverability, and server identification, but it works best when your broader DNS setup is correct. These related guides explain reverse DNS, standard DNS records, and DNS zones in more detail:
