Creating a PTR Record

Scenarios

PTR records are used to prove credibility of IP addresses and domain names of email servers. Most spam senders use email servers whose IP addresses are dynamically allocated or not mapped to registered domain names in order to avoid being tracked. If you do not want emails sent from your mail server to be considered as spam, add a PTR record to map the email server IP address to a domain name. In this way, the email recipient 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 ECS IP address to a domain name.

This section describes how to add a PTR record for a cloud resource, such as ECS.

Constraints

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

Prerequisites

• You have registered a domain name.
• You have created an ECS and bound an EIP to it.

Procedure

1. Log in to the management console.
2. In the service list, choose Network > Domain Name Service.

   The DNS console is displayed.

3. In the navigation pane, choose PTR Records.

   The PTR Records page is displayed.

4. Click in the upper left corner and select the desired region and project.
5. Click Create PTR Record.
6. Set 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
   Name	Domain name mapped to the EIP.	www.example.com
   TTL (s)	Cache duration period of the PTR record, in seconds The default value is 300, which is, 5 minutes.	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.	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 or contain special characters =*<>\,|/	example_key1
   Value	Cannot be left blank. Can contain a maximum of 43 characters. Cannot start or end with a space or contain special characters =*<>\,|/	example_value1

7. Click OK.

   View the created PTR record on the PTR Records page.

   NOTE:

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

8. Verify that the PTR record has taken effect.

   Run the following DOS command on a PC connected to the Internet:

   nslookup -qt=ptr IP address