Network & protection
Set and verify reverse DNS
Save a desired PTR hostname for an assigned address, understand the current propagation limitation, and verify the public DNS answer independently.
On this page
Before you start
- An IPv4 or IPv6 assignment displayed for a server in Account > Network.
- A fully qualified hostname under a DNS zone you control, such as host.example.com.
- A forward A or AAAA record for that hostname when forward-confirmed reverse DNS is required by your service.
- The dig utility from BIND 9, or another standards-aware DNS lookup tool, for independent verification.
Understand the two DNS directions
Forward DNS maps a hostname to an address through an A record for IPv4 or an AAAA record for IPv6. Reverse DNS maps an address back to a hostname through a PTR record in a reverse zone controlled by the address holder. Creating a forward record in your own zone does not create the PTR, and saving a PTR request does not create the forward record.
Choose one stable, fully qualified hostname. The form accepts lower-case DNS names with labels separated by dots and can also clear the stored value. It does not accept an IP literal or a single unqualified label. Avoid placing customer names or sensitive roles in a public hostname because PTR answers are visible to anyone.
Prepare matching forward DNS
Forward-confirmed reverse DNS is a consistency pattern used by some mail and security systems, but it does not establish reputation or guarantee service acceptance. Follow the policies of the application you operate and never use reverse DNS to imply ownership you do not have.
- Choose a hostname in a zone you administer.
- Create the matching A record for an IPv4 address or AAAA record for an IPv6 address with your DNS provider.
- Wait for that forward record to answer through the public DNS.
- Confirm that the hostname resolves back to the exact assigned address before requesting its PTR.
- Document the intended hostname, address, and change time.
Save the desired PTR
- Open Account > Network and identify the exact IPv4 or IPv6 assignment.
- Enter the fully qualified hostname in that row’s Reverse DNS field.
- Select Save rDNS and retain the success message in your change record.
- Contact the operator with the address, desired hostname, server name, and time of the saved request.
- Wait for operator confirmation before treating the change as published.
Verify the public answer
Use dig with -x to perform a reverse lookup. The option constructs the correct in-addr.arpa or ip6.arpa query, so do not hand-build the reverse name. Query both the reverse result and the forward hostname. A blank reverse result after saving is expected until the operator applies the change; it is not fixed by repeatedly resubmitting the form.
dig +noall +answer -x 192.0.2.10
dig +noall +answer host.example.com A
dig +noall +answer -x 2001:db8::10
dig +noall +answer host.example.com AAAA| Observation | Meaning | Next step |
|---|---|---|
| Stored value, no PTR answer | The change may not be published yet, or a cached answer may still be in use. | Provide the saved request to the operator. |
| PTR answers, forward record differs | Forward and reverse DNS are inconsistent | Correct the A or AAAA record you control. |
| Old PTR still answers | Cache or authoritative zone still has the prior value | Check authoritative status with the operator and allow the published TTL. |
| Wrong assignment row | The request targeted another address | Correct the desired value and report any published error immediately. |