Manage PTR records

This topic explains how to add and manage PTR records, including the required procedures and key considerations.

Prerequisites

Before you begin, ensure that the following requirements are met:

Supported IP resources: You can configure PTR records only for an Elastic IP Address (EIP) or a static public IP address of an ECS instance in your Alibaba Cloud account.
Supported IP version: Only IPv4 addresses are supported.

Add a PTR record

Navigate to the Alibaba Cloud DNS - Reverse DNS Lookup page.
Click Add PTR record.

Fill out the form to create the PTR record.

Parameter	Description
Public IP region	Select the region where your public IP resource is located. Note Alibaba Cloud DNS retrieves the public IP resources (EIPs or static public IP addresses of ECS instances) associated with your account from the selected region. Alibaba Cloud DNS then verifies the IP address that you enter against these resources. If the verification fails, you cannot add the PTR record.
Public IP (EIP or a static IP)	Enter the public IPv4 address for the reverse DNS lookup. You can add only one PTR record for each IP address.
PTR record name	The system automatically generates this based on the public IP address that you provide. The system creates the PTR record name by reversing the four octets of the IPv4 address you entered in the Public IP (EIP or a static IP) field and appending `in-addr.arpa`. For example, if the IP address is `1.2.3.4`, the PTR record name becomes `4.3.2.1.in-addr.arpa`. Ensure that the PTR record name is globally unique.
TTL	This value specifies how long DNS resolvers cache this record. The default value is 10 minutes. We recommend that you set this to the same value as the corresponding record in your authoritative DNS. For more information, see How to configure TTL. The value can range from 1 second to 24 hours.
Record Values	Enter the domain name for the IP address and complete the domain ownership verification. Enter the domain name, such as `example.com`. Wildcard domains are not supported. Click Verify TXT Record. A red message appears at the bottom of the Record values section, prompting you to complete the verification. Find and click the TXT authorization verification link. In the Domain owner verification dialog box, copy the system-generated Hostname (for example, `alidnsptrcheck`) and Record Value, which is an auto-generated verification string. Go to your domain's DNS provider and add a TXT record for the root domain, 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 succeeds, you can continue. Note For public-facing services such as mail servers, we recommend that you configure a single record value for each IP address that points to its canonical hostname. Doing so ensures compatibility and credibility.

A red message appears below the Alibaba Cloud Public IP (EIP or ECS static public IP address) field, stating that if the public IP address is released or reclaimed, the system automatically deletes the associated PTR record.

Modify a PTR record

Navigate to the Alibaba Cloud DNS - Reverse DNS Lookup page.
Find the target record and click Edit in the Actions column.
Modify the PTR record and submit your changes.

Note
Local DNS resolvers cache records based on their TTL value. Changes to a record take effect only after the cache for the previous record expires. For example, if the original TTL was 10 minutes and you change the record and set the new TTL to 1 second, the change may take up to 10 minutes to propagate globally. The new record and TTL will propagate after local DNS resolvers refresh their cache from Alibaba Cloud DNS.

Optimization suggestion: To apply changes more quickly, first lower the TTL value and wait for the original TTL duration to pass. Then, modify the record content. This method significantly reduces propagation time.

Disable or delete a PTR record

If you no longer need a PTR record, you can disable or delete it. The change will be fully effective across the internet after existing caches expire, which may take up to 24 hours.

Important

In addition to manual deletion, the system periodically inspects and reclaims invalid PTR records. For more information, see PTR record reclamation mechanism.

Navigate to the Alibaba Cloud DNS - Reverse DNS Lookup page.
Find the target record.
- Disable a record: In the Status column, toggle the switch to disable the PTR record.
  
  Important
  A disabled PTR record is inactive but remains billable.
- Delete a record: To permanently remove a record and stop incurring charges:
  - In the Actions column for the target record, click Delete.
  - In the confirmation dialog box that appears, confirm the deletion.

FAQ

TXT authorization verification failure

You can troubleshoot the issue by following these steps:

Verify the TXT record: Ensure that the host record and record value you added at your DNS provider exactly match the values provided by Alibaba Cloud DNS, with no extra or missing characters.
Wait for DNS propagation: DNS changes take time to propagate globally. The duration depends on your DNS provider and TTL settings. Wait a few minutes and then click Verify again.
Use a diagnostic tool: Use a command-line tool such as dig or nslookup to check if the TXT record has propagated. For example, run dig TXT alidnsptrcheck.yourdomain.com and check if the returned record value is correct.

Error: PTR IP information mismatch

You can add PTR records only for an Elastic IP Address (EIP) or a static public IP address of an ECS instance in your Alibaba Cloud account. This feature does not support public IP addresses of Simple Application Server instances or public IP addresses that belong to other Alibaba Cloud accounts.