I have 3 projects in Google Cloud Platform. All have the default VPC Network, subnets etc. I have successfully peered a single project with a MongoDB Atlas cluster. However if I want to peer a second project it is not possible as there are overlapping subnet IP address ranges, since they are all created with the same default values.
What options do I have?
Can I use a Shared VPC network for all three GCP project and peer that with MongoDB Atlas?
If you have a project and want to peer one more with the same network and subnet values , it's impossible and as per Your requirement can create a new VPC and that doesn't overlap.
To create new VPC, Go to the VPC networks page in the Google Cloud Console > Create VPC network > Enter a Name for the network > Choose Custom for the Subnet creation mode > New subnet > Provide a Name for the subnet > region > IP address range > if you want to define a secondary range for the subnet, click Create secondary IP range > you can Choose whether to enable Private Google Access for the subnet when you create it or later by editing it > you can Choose whether to enable VPC flow logs for the subnet when you create it or later by editing it > click Done > To add more subnets, click Add subnet and repeat the previous steps > Choose the Dynamic routing mode for the VPC network > you can Choose whether the network has an MTU of 1460 (default) or 1500. Review the MTU information in the concepts guide before setting the MTU to 1500 > Click Create.