Using external DNS

Overview

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

Velostrata provides a way to set and control the external DNS settings of migrated VMs. To do this, you configure DNS settings in the Google Cloud project (and region) using Google Cloud project metadata. These settings are applied to new VMs as they are migrated.

Note: DHCP retrieves the primary IP address, subnet masks, gateway, and other necessary network details.

When empty DNS metadata is provided (such as default-dns-servers = ""), DHCP overwrites the DNS configuration.

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.

Configuring external DNS data on VMs in GCP

To enable external DNS on migrated VMs:

1. In the Google Cloud Platform 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 with a region setting

1. If your VMs have a specific region setting, add the following key-value pairs in the Metadata page:
   1. Key: {region_name}_dns-domain-name Value: : mydomain.com - represents the connection-specific DNS suffix in Windows clients.
   2. Key: {region_name}_dns-servers Value: : {comma separated list of IPs}- represents the list of DNS servers.
   3. Key: {region_name}_dns-domain-suffixes Values: mydomain.com, myseconddomain.com - represents the list of DNS suffixes to add to Windows and Linux machines.
2. When you're done, click Save.

Using VMs without a region setting (default configuration)

1. If your VMs don't have a specific region setting, add the following key-value pairs in the Metadata page:
   1. Key: default_dns-domain-name Value: mydomain.com
   2. Key: default_dns-servers Value: {comma separated list of IPs}
   3. Key: default_dns-domain-suffixes Value: mydomain.com, myseconddomain.com
2. When you're done, click Save.