Using external DNS

Overview

Google Cloud VPC networks have an internal DNS service and do not automatically support configuring external DNS for a VM. Enterprises, however, might prefer to manage their own DNS servers directly and need to configure external DNS on migrated VMs.

Migrate for Compute Engine provides a way to set and control the external DNS settings of migrated VMs. To do this, configure DNS settings in the Google Cloud project using Google Cloud project metadata. These settings are applied to new VMs as they are migrated.

As an alternative, Google Cloud offers a standalone DNS forwarding solution as part of Cloud DNS. Cloud DNS works with all resources in a Virtual Private Cloud and provides DNS resolution of names both on-premises and on Google Cloud.

How DNS settings are applied

The DNS settings are applied as follows:

• For Windows clients, the key-value pairs are applied to all NICs as follows:
  • dns-domain-name: Replaces the DNS suffix for this connection setting per NIC.
  • dns-servers: Replaces the list of DNS servers per NIC.
  • dns-domain-suffixes: Replaces the list of DNS suffixes per NIC.
• For Linux clients, the key-value pairs are applied to all NICs as follows:
  • dns-servers: Prepends the list of DNS servers in the resolv.conf file.
  • dns-domain-suffixes: Prepends the list of DNS suffixes in the resolv.conf file.

Note: When DNS metadata is empty (default-dns-servers = ""), Migrate for Compute Engine uses DHCP DNS configuration.

Configuring your VMs to connect to the metadata server

Google Cloud provides metadata to VMs hosted on Compute Engine. To use external DNS without forwarding to Cloud DNS, you need to configure name resolution for your VMs manually.

To do so, add the following line to the /etc/hosts file (on Linux) or c:\Windows\System32\Drivers\etc\hosts (on Windows).

169.254.169.254 metadata.google.internal

Note: Automating this step is possible with scripted custom adaptations.

Configuring external DNS data on VMs in GCP

To enable external DNS on migrated VMs:

1. In the Google Cloud console, go to the Metadata page for your project.
2. Under Metadata, click Edit.

   

   Enabling external DNS (click to enlarge)

3. In the Metadata page, add the appropriate key:value pairs. Use one of the following sections for instructions for these deployments:
   • If your VMs have a region setting, follow the instructions in Using VMs with a region setting.
   • If your VMs don't have a region setting, follow the instructions in Using VMs without a region setting to use the default configuration.

Note: A region setting takes priority over a default setting.

Using VMs without a region setting (default)

1. If your VMs don't have a specific region setting, add the following key-value pairs in the Metadata page:

   Key	Example Value
   {region_name}_dns-domain-name	: mydomain.com
   {region_name}_dns-servers	: {comma separated list of IPs}
   {region_name}_dns-domain-suffixes	mydomain.com, myseconddomain.com

2. When you're done, click Save.

Using VMs with a region setting

1. If your VMs have a specific region setting, add the following key-value pairs in the Metadata page:

   Description	Key	Example Value
   Windows clients	{region_name}_dns-domain-name	: mydomain.com
   List of DNS servers	{region_name}_dns-servers	: {comma separated list of IPs}
   represents the list of DNS suffixes to add to Windows and Linux machines.	{region_name}_dns-domain-suffixes	mydomain.com, myseconddomain.com

2. When you're done, click Save.