Alibaba Cloud DNS:Manage PTR records

Add a PTR record

1. Go to Alibaba Cloud DNS - Reverse DNS Lookup.

2. Click Add PTR record.

   

3. Fill in and submit the form to create the PTR record.

   Form Item	Description
   Public IP region	Enter the region where the public IP resource is located. Note Alibaba Cloud DNS retrieves the public IP resources (EIPs or static public IP addresses of ECS instances) that you own in the specified region. It then verifies them against the IP address that you enter. If the verification fails, you cannot add the PTR record.
   Public IP (EIP or a static IP)	Enter the public IP address for which you want to configure reverse DNS lookup. Only the IPv4 format is supported. You can add only one PTR record for each IP address.
   PTR record name	This is generated based on the Alibaba Cloud public IP address that you enter. The PTR record name is generated by reversing the four octets of the IPv4 address entered for Public IP (EIP or a static IP) and appending in-addr.arpa. For example, if the IP address is 1.2.3.4, the final PTR record name is 4.3.2.1.in-addr.arpa. Make sure the PTR record name is globally unique.
   TTL	Set the duration for which the record is cached on a DNS server. The default value is 10 minutes. Set this to the same value as the public authoritative DNS record. For more information, see How to configure TTL. Supported range: 1 second to 24 hours.
   Record Values	Set the target domain name to which the IP address maps and complete the domain name ownership verification. In the input box, enter a domain name, such as example.com. Wildcard domain names are not supported. Click Verify TXT Record. In the dialog box that appears, copy the system-generated Hostname (such as alidnsptrcheck) and Record Value. Go to your domain name's DNS provider and add a TXT record for the root domain name, such as example.com. Use the Hostname and Record Value that you copied. Return to the dialog box on the Add PTR record page and click Verify. After the verification is successful, you can proceed. Note For public network services such as mail servers, set only one record value for each IP address. The record value should point to the unique canonical hostname of the IP address. This ensures compatibility and credibility.

   

Modify a PTR record

1. Go to Alibaba Cloud DNS - Reverse DNS Lookup.

2. Find the target record and click Edit in the Actions column.

   

3. Modify the record and click OK to save your changes.

   Note

   Local DNS servers cache a record for the duration of its Time to Live (TTL). A record is updated from the authoritative server only after the TTL of the cached version expires. Changing a record or lowering its TTL on the authoritative server does not affect results that are already cached. You must wait for the previous TTL to expire before local DNS servers retrieve the updated record. For example, if the original TTL was 10 minutes and you change the record content and set the new TTL to 1 second, you still need to wait up to 10 minutes for the change to propagate. The new record content and TTL take effect only after the cache on local DNS servers expires and they retrieve the new record from Alibaba Cloud DNS.

   Optimization suggestion: To make changes take effect faster, first lower the TTL to a small value and wait for the original TTL period to expire. Then, you can modify the record content. This method can significantly shorten the time it takes for the change to propagate.

Disable or delete a PTR record

If you no longer need a PTR record, you can disable or delete it. The record becomes invalid after its TTL expires. This process can take up to 24 hours.

• Go to Alibaba Cloud DNS - Reverse DNS Lookup.

• Find the target record.

  • Disable a record: In the Status column, click the switch for the PTR record.

    

    Important

    After you disable a PTR record, it becomes invalid, but you are still charged for retaining it.

  • Delete a record: You can permanently delete a record to stop incurring charges.

    • In the Actions column for the target record, click Delete.

      

    • Confirm the deletion in the dialog box that appears.

FAQ

What do I do if TXT authorization verification fails?

Troubleshoot the issue as follows:

1. Confirm that the record was added correctly: Make sure the host and record value of the TXT record that you added at your DNS provider are identical to the values provided by Alibaba Cloud DNS. Ensure that there are no extra or missing characters.

2. Wait for DNS propagation: A DNS record requires time to take effect globally. The propagation time depends on your DNS provider and TTL settings. Wait a few minutes and then click Verify again.

3. Use verification tools: Use command-line tools such as dig or nslookup to check whether the TXT record has propagated. For example: dig TXT alidnsptrcheck.yourdomain.com. Check whether the returned record value is correct.

Why do I receive the error "PTR IP information mismatch. The IP may no longer belong to the current user." when I add a PTR record?

You can add PTR records only for EIPs and static public IP addresses of ECS instances that are in your Alibaba Cloud account. You cannot add PTR records for the public IP addresses of Simple Application Server instances or for public IP addresses that belong to other Alibaba Cloud accounts.