Updated on 2024-03-15 GMT+08:00

Creating a PTR Record

Scenarios

PTR records are used to prove credibility of IP addresses and domain names of email servers. To avoid being tracked, most spam senders use email servers whose IP addresses are dynamically allocated or not mapped to registered domain names. If you want to keep the spam out of your recipients' inbox, add a PTR record to map the email server IP address to a domain name. In this way, the email recipients can obtain the domain name by IP address and will know that the email server is trustworthy.

If you use an ECS as an email server, configure a PTR record to map the EIP of the ECS to the domain name.

PTR records take effect only after the name servers are configured. After you create a PTR record, we will contact CNNIC and APNIC to configure the name servers and allow Huawei Cloud DNS for domain name resolution. This process takes about 1 to 3 working days. In case of urgency, submit a service ticket. We will contact CNNIC and APNIC to speed up the process.

This following are operations for you to add a PTR record for a cloud resource, such as ECS.

Constraints

You can only configure PTR records for IP addresses with a 32-bit subnet mask.

Prerequisites

  • You have registered a domain name with Huawei Cloud or a third-party registrar.
  • You have created an ECS and bound an EIP to it.

Procedure

  1. Go to the PTR Records page.
  2. Click in the upper left corner and select the desired region and project.
  3. Click Create PTR Record.
    Figure 1 Creating a PTR record
  4. Configure the parameters based on Table 1.
    Table 1 Parameters for creating a PTR record

    Parameter

    Description

    Example Value

    EIP

    EIP of another cloud resource, for example, ECS.

    You can select an EIP from the drop-down list.

    XX.XX.XX.XX

    Domain Name

    Domain name mapped to the EIP.

    example.com

    TTL (s)

    Cache duration of the PTR record, in seconds

    The default value is 300s.

    300

    Tag

    (Optional) Identifier of the PTR record.

    Each tag contains a key and a value. You can add a maximum of 10 tags to a PTR record.

    For details about tag key and value requirements, see Table 2.

    NOTE:

    If you have configured tag policies for DNS, you need to add tags to your PTR records based on the tag policies. If you add a tag that does not comply with the tag policies, PTR records may fail to be created. Contact the administrator to learn more about tag policies.

    example_key1

    example_value1

    Description

    (Optional) Supplementary information about the PTR record.

    The description of the PTR record

    Table 2 Tag key and value requirements

    Parameter

    Requirements

    Example Value

    Key

    • Cannot be left blank.
    • Must be unique for each resource.
    • Can contain a maximum of 36 characters.
    • Cannot start or end with a space nor contain special characters =*<>\,|/

    example_key1

    Value

    • Cannot be left blank.
    • Can contain a maximum of 43 characters.
    • Cannot start or end with a space nor contain special characters =*<>\,|/

    example_value1

  5. Click OK.

    You can view the created PTR record on the PTR Records page.

    If a domain name is mapped to multiple EIPs, you must create a PTR record for each EIP.

  6. Verify that the PTR record has taken effect by running the following command on a PC connected to the Internet:

    nslookup -qt=ptr EIP