# How Can I Configure a PTR Record to Map the IP Address of an ECS to a Domain Name?

PTR records enable users to query domain names based on IP addresses.

To map the private IP address of an ECS to a domain name, you must create a private zone and create a PTR record in the zone.

To map the EIP of the ECS to a domain name, refer to Creating a PTR Record.

The domain name in a PTR record must be in the x.x.x.x.in-addr.arpa format. in-addr.arpa is the domain name suffix used for reverse resolution.

For example, if the private IP address is 192.168.1.10, the domain name in the PTR record must be 10.1.168.192.in-addr.arpa.

In this case, you must create a private zone named 192.in-addr.arpa and add a PTR record with its value set to 10.1.168.192.in-addr.arpa.

#### Creating a Private Zone

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 Private Zones.

   The Private Zones page is displayed.

4. Click in the upper left corner and select the desired region and project.
5. Click Create Private Zone.
   Figure 1 Create Private Zone
6. Set the parameters based on Table 1.

   Table 1 Parameters for creating a private zone
   Parameter | Description | Example Value
   --- | --- | ---
   Name | Domain name Set the domain name suffix to in-addr.arpa. | 192.in-addr.arpa
   VPC | VPC to be associated with the private zone Select the VPC you want to associate with the private zone. | N/A
   Email | (Optional) Email address of the administrator managing the private zone It is recommended that you set the email address to HOSTMASTER@Domain name. For more information about the email address, see Why Was the Email Address Format Changed in the SOA Record? | HOSTMASTER@example.com
   Tags | (Optional) Identifier of a resource Each tag contains a key and a value. You can add a maximum of 20 tags to a zone. For details about tag key and value requirements, see Table 2. | example_key1 example_value1
   Description | (Optional) Supplementary information about the zone You can enter a maximum of 255 characters. | This is a private zone.

   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.

   example_key1

   Value

   - Cannot be left blank.
   - Can contain a maximum of 43 characters.

   example_value1

7. Click OK.
8. Switch back to the Private Zones page.
   View the created private zone.

   Click the zone name to view zone details. You can view SOA and NS record sets automatically generated by the system.

   - The SOA record set defines the DNS server that is the authoritative information source for a particular domain name.
   - The NS record set defines authoritative DNS servers for a zone.

#### Adding a PTR Record

1. On the Private Zones page, click the name of the private zone that you have created.

   The Record Sets page is displayed.

2. Click Add Record Set.

   The Add Record Set dialog box is displayed.

   Figure 2 Add Record Set
3. Set the parameters based on Table 3.

   Table 3 Parameters for adding a PTR record
   Parameter | Description | Example Value
   --- | --- | ---

   Name

   IP address in the PTR record (typed in reverse order)

   10.1.168

   For example, if the IP address is 192.168.1.10, the domain name in the PTR record is 10.1.168.192.in-addr.arpa.
   - If the private zone name is 192.in-addr.arpa, enter 10.1.168 in the box.
   - If the private zone name is 1.168.192.in-addr.arpa, enter 10 in the box.

   Type | Type of the record set | PTR – Map IP addresses to domains
   TTL (s) | Cache duration of the record set, in seconds | The default value is 300, which is, 5 minutes.
   Value | Domain name mapped to the IP address You can enter only one name. | mail.example.com
   Tags | (Optional) Identifier of a resource Each tag contains a key and a value. You can add a maximum of 20 tags to a record set. For details about tag key and value requirements, see Table 2. | example_key1 example_value1
   Description | (Optional) Supplementary information about the PTR record | The PTR record is for reverse resolution.

4. Click OK.
5. Switch back to the Record Sets page.

   View the added record set in the record set list of the zone and ensure that the status of the record set is Normal.

Parent topic: Private Zones