Create a PTR record for a VM instance (original) (raw)

ConfigurablePTR recordslet you define the reverse DNS record associated with the external IP address of a VM instance so that applications that rely on these records can operate as intended.

Some applications require reverse DNS records (PTR records) to resolve IP addresses to domain names. For example, applications that use SMTP require a PTR record that points to the domain from which an email is being sent. Without that record, spam filters can mark emails with low reputation, which causes email to end up in spam folders or not be sent at all.

You can add PTR records to only the primary network interface of a VM instance. PTR records are not available for load balancer frontends,Cloud NAT, or other non-VM IP addresses.

IPv6 PTR records are only available if the instance's primary network interface is connected to a dual-stack or IPv6-only subnet that has an external IPv6 address range. For dual-stack network interfaces, you can have separate IPv4 and IPv6 PTR records.

To create custom PTR records that override the automatically created internal DNS PTR names, seeManaged reverse lookup zones.

Before you begin

Verify your domain ownership

Before you create a VM with a custom PTR record, verify that you own the domain name. Verifying ownership is a security measure to prove to Google that you are the domain owner.

You can verify your domain name in 2 ways:

Verify by using Search Console

  1. Open Search Consoleand sign in by using the Google Account that you will use to add a PTR record to your instance. You can verify domain ownership with multiple accounts.
  2. Enter the PTR domain name.
  3. Click Continue.
  4. Follow the instructions, and then click Go to Property.
  5. Click on Settings (found in the menu on the left near the bottom), and then click Ownership Verification.

After you verify that you own the domain, in the Settings pane, click on Users to see other verified owners. To add PTR records in other domains, click the property picker on the left that displays your current domain. Click Add a property to add those domains.

If your domain name is not immediately verified, use the Recommended Methodto obtain verification.

Verify by adding your VM's IP address to your DNS configuration

  1. If your VM does not exist yet, reserve a regional static external IP addressand use it later during VM creation.
  2. Add an "A" record with the VM's external IP address to the DNS configuration of your domain.

Create VM instances with PTR records

You can specify PTR records when you create new instances. To add a PTR record for an existing instance, seeAdd PTR records.

Console

  1. In the Google Cloud console, go to the Create an instance page.
    Go to Create an instance
  2. Specify the VM details.
  3. Expand the Advanced options section, and then do the following:
    1. Expand the Networking section.
    2. Create one or more network interfaces to use with this VM. Alternatively, you can use the default network interface.
    3. In the Network interfaces section, expand the first network interface, which is the primary network interface.
    4. In the Public DNS PTR record section, select each type of PTR record that you want to add.
    5. In the PTR domain name field, enter a domain name for each type of PTR record that you want to add.
    6. In the External IPv4 address or External IPv6 address field, choose your previously reserved IP address. If you have verified your VM's IP address through your DNS configuration, then you must specify that address.
    7. To confirm the network interface settings, click Done.
  4. Configure the remaining properties for your new VM.
  5. At the bottom of the page, click Create.

After the VM starts, you can run a reverse DNS lookup on the external IP address of your VM to confirm that the PTR record is working as expected.

gcloud

REST

Add PTR records

You can add PTR records by updating the access configuration on the primary network interface, nic0, of a VM instance.

Console

  1. In the Google Cloud console, go to the VM instances page.
    Go to VM instances
  2. Click the instance that you want to edit.
  3. Click Edit.
  4. In the Network interfaces section, click the primary network interface.
  5. In the Public DNS PTR record section, select each type of PTR record that you want to add.
  6. In the PTR domain name field, enter a domain name for each type of PTR record that you want to add.
  7. Click Done, and then click Save.

gcloud

  1. If your VM doesn't have an access configuration, add one by using thegcloud compute instances add-access-config command.
    gcloud compute instances add-access-config INSTANCE_NAME
    Replace INSTANCE_NAME with the name of your instance.
  2. Update the access configuration to add the PTR record by using thegcloud compute instances update-access-config command. To add both IPv4 and IPv6 PTR records, use the following commands individually.
    • For IPv4:
      gcloud compute instances update-access-config INSTANCE_NAME \
      --public-ptr \
      --public-ptr-domain DOMAIN_NAME
    • For IPv6:
      gcloud compute instances update-access-config INSTANCE_NAME \
      --ipv6-public-ptr-domain=DOMAIN_NAME

Replace the following:

REST

  1. If your VM doesn't have an access configuration, add one by making a POST request to theinstances.addAccessConfig method.
    POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/instances/INSTANCE_NAME/addAccessConfig?networkInterface="nic0"
  2. Update the access configuration to add the PTR record by making a POSTrequest to theinstances.updateAccessConfig method. To add both IPv4 and IPv6 PTR records, make the following requests individually.

Remove PTR records

To remove PTR records, update the access configuration on the primary network interface, nic0, of a VM instance. When you remove a PTR record, Google Cloud responds to reverse DNS lookups with a default fully qualified domain name of googleusercontent.com.

Console

  1. In the Google Cloud console, go to the VM instances page.
    Go to VM instances
  2. Click the instance that you want to edit.
  3. Click Edit.
  4. In the Network interfaces section, click the primary network interface.
  5. In the Public DNS PTR record section, clear the checkbox for each type of PTR record that you want to remove.
  6. Click Done, and then click Save.

gcloud

To remove a PTR record, use thegcloud compute instances update-access-config command. To remove both IPv4 and IPv6 PTR records, use the following commands separately.

Replace INSTANCE_NAME with the name of the instance to update.

REST

To remove a PTR record, make a POST request to theinstances.updateAccessConfig method. To remove both IPv4 and IPv6 PTR records, make the following requests individually.

Replace the following:

Limitations

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