Networking
Reverse DNS (rDNS)
Set, verify, or remove the hostname returned for one of your public IPv4 addresses.
Reverse DNS maps an IP address to a hostname using a PTR record. Forward DNS maps a hostname to an address using an A record. You manage the A record at your domain's DNS provider and the PTR record in the Serverside.com console.
The current reverse-DNS service supports IPv4. You need permission to manage network addresses and access to the hostname's DNS records.
Prepare the hostname
Choose a fully qualified hostname, such as server.example.com, and create its public A record pointing to the server's assigned IPv4 address. For example:
| Record | Name or address | Value |
|---|---|---|
| A, at your DNS provider | server.example.com | 198.73.57.2 |
| PTR, in the Serverside.com console | 198.73.57.2 | server.example.com |
Replace both values with your own hostname and assigned address. The A record must resolve publicly to that IP before the PTR can be saved. If the hostname has several A records, at least one must match.
Assign the address to its server before configuring reverse DNS. See Public IP Blocks for address assignment.
Set or remove the record
- Open Virtual Networks in the cloud console and select the network containing the IP block.
- Open Prefixes, then select Manage beside the block.
- Find the address and select its Edit reverse DNS pencil control.
- Enter the hostname, without a URL scheme or path, and select Save.
To change the hostname, create the replacement hostname's A record first, then edit and save the PTR. To remove it, reopen the same dialog and select Remove Record. Removing reverse DNS does not release the IP address or remove the A record at your DNS provider.
Unassigning or releasing an address removes its PTR record. Set it again after reassigning the address if needed.
Verify and troubleshoot
Check the forward and reverse lookups, replacing these example values:
nslookup -type=A server.example.com 1.1.1.1
nslookup 198.73.57.2 1.1.1.1
The first lookup should include your server's IP; the second should return the hostname you saved. DNS resolvers may keep an earlier answer until its cache expires.
- No A record: create the public A record and wait until it resolves before saving again.
- A record mismatch: correct the A record so its public answer includes this IP.
- Temporary lookup or provider error: follow the console's retry delay. Contact support if it persists, including the IP, hostname, and error message.
See reverse DNS through the API for automation.
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