Reverse DNS

Reverse DNS (rDNS) maps an IP address back to a hostname, using a PTR record. It’s the opposite of a normal DNS lookup, which maps a hostname to an IP address.

You can set the reverse DNS for any IPv4 or IPv6 address assigned to your SSD VPS yourself, from the Control Panel or the REST API. Changes are applied straight away.

Reverse DNS is commonly needed when:

• You run a mail server. Many receiving mail servers reject or flag email from IP addresses without a matching PTR record.
• You want logs, traceroute output and other tools to show a meaningful hostname for your server instead of a generic one.

Before you start

Reverse DNS must be forward-confirmed. Before you can set a hostname for an IP address, that hostname must already resolve to the same IP address:

IP address type	Required forward record
IPv4	An A record pointing to the IP address
IPv6	An AAAA record pointing to the IP address

For example, to set the reverse DNS for 203.0.113.10 to mail.example.com, first create an A record for mail.example.com with the value 203.0.113.10 at your DNS provider. You can check the record has taken effect with:

dig +short A mail.example.com

Allow time for new DNS records

If you have just created or changed the A or AAAA record, it can take a few minutes, or longer depending on your DNS provider, before it can be looked up. If saving reverse DNS fails because the hostname doesn’t resolve to your IP address, wait a little and try again.

Set or change reverse DNS

1. Navigate to the relevant server page and select the Network tab.

2. In the IP Addresses table, find the IP address you want to update. The RDNS column shows its current hostname, or Set hostname if none is set. Select the hostname or Set hostname to open the Reverse DNS dialogue.

3. Enter the fully qualified hostname in the Hostname field, for example mail.example.com.

4. Select Save, or press Enter.

Once saved, the dialogue closes and the RDNS column shows the new hostname. If the hostname can’t be saved, an error message is shown in the dialogue so you can correct it and try again. See Troubleshooting for common errors.

Remove reverse DNS

1. Navigate to the relevant server page and select the Network tab.

2. In the IP Addresses table, select the hostname in the RDNS column for the IP address.

3. Select Remove in the Reverse DNS dialogue.

What happens next depends on the IP address:

• Most IPv4 addresses are reset to a generic hostname based on the IP address, in the form <hex-ip>.static.setaptr.net. For example, 31.24.224.10 is reset to 1f18e00a.static.setaptr.net.- IPv6 addresses, and IPv4 addresses outside our standard ranges, have their PTR record deleted.

Reverse DNS is reset automatically

When an IP address is removed from your server, or the server is destroyed, its reverse DNS is reset in the same way. A hostname you set is never left pointing at an IP address that has been reassigned to another customer.

Use the REST API

You can also manage reverse DNS with the ICS REST API. Replace {location-id}, {server-id} and the IP address with your own values, and API_KEY with your API key.

Set reverse DNS

curl --request PUT \
  --url https://api.ingenuitycloudservices.com/rest-api/ssd-vps/locations/{location-id}/servers/{server-id}/ip-addresses/203.0.113.10/rdns \
  --header 'Accept: application/json' \
  --header 'Content-Type: application/json' \
  --header 'X-Api-Token: API_KEY' \
  --data '{"hostname":"mail.example.com"}'

Remove reverse DNS

curl --request DELETE \
  --url https://api.ingenuitycloudservices.com/rest-api/ssd-vps/locations/{location-id}/servers/{server-id}/ip-addresses/203.0.113.10/rdns \
  --header 'Accept: application/json' \
  --header 'X-Api-Token: API_KEY'

The same forward-confirmation rules apply to API requests. If a request fails, the response contains the same error message that the Control Panel shows.

Troubleshooting

Error	What to do
mail.example.com must resolve to 203.0.113.10 (A record) before reverse DNS can be set.	The hostname’s A record (or AAAA record for IPv6) doesn’t point to this IP address. Create or correct the record at your DNS provider, wait for it to take effect, and try again.
We couldn’t look up mail.example.com right now. Check its A/AAAA record exists and try again.	The hostname couldn’t be looked up. Check that the domain is registered and its A or AAAA record exists, then try again.
Enter a valid hostname, for example server.example.com.	Enter a fully qualified hostname, such as mail.example.com. IP addresses, URLs and names without a domain aren’t accepted.
Reverse DNS can’t be set to a name in a major email provider’s domain.	To protect against email spoofing, hostnames in the domains of major email providers, such as Google, Microsoft and Yahoo, can’t be used. Use a hostname in a domain you own.
Reverse DNS isn’t managed for this IP address.	Reverse DNS for this IP address can’t be changed from the Control Panel. Please contact our support team.
Reverse DNS isn’t available right now. or We couldn’t reach the reverse DNS service. Please try again later.	The reverse DNS service is temporarily unavailable. Please try again later, or contact our support team if the problem continues.

Seeing the old hostname?

Your change takes effect on our nameservers immediately, but other DNS resolvers may have the previous PTR record cached for up to an hour. You can check our nameservers directly with dig +short -x 203.0.113.10 @ns1.ingenuitycloudservices.com.