Resolving Issues with Cloud Deployment Manager Templates

D.

When a VPC network is created, it is created in Auto mode by default, which means that Google automatically creates subnets in each region that are automatically allocated IP ranges. In custom mode, the VPC network administrator has greater control over the IP address ranges and subnets.

If Cloud Deployment Manager templates are not working after converting the VPC network from auto mode to custom mode, it's likely because the templates were referencing resources that were created in the auto mode VPC network.

To resolve the problem, option D, "explicitly reference the custom mode networks in the Deployment Manager templates" is the most appropriate solution. This means that you need to update the Deployment Manager templates to reference the new resources created in the custom mode VPC network.

Option A, "apply an additional IAM role to the Google API's service account to allow custom mode networks," is not a solution because IAM roles are used to control access to Google Cloud resources and not to allow custom mode networks.

Option B, "update the VPC firewall to allow the Cloud Deployment Manager to access the custom mode networks," is not a solution because VPC firewall rules are used to control traffic to and from instances in the VPC network and not to allow access to custom mode networks.

Option C, "explicitly reference the custom mode networks in the Cloud Armor whitelist," is not a solution because Cloud Armor is a DDoS and application defense service that provides security policy enforcement for VPC networks and not for resolving issues with Deployment Manager templates.