My company's infrastructure is hosted on Google Cloud. We'd like to connect a network of one our clients with site-to-site (IPSec) VPN. I've setup one on Google Cloud but we have a problem. Our subnetwork (10.10.0.0/16) is overlapping with their subnetworks (10.10.0.0/24). We have to solve this on our end, so on Google Cloud. Any idea how we can achieve this? I tried to add a new network interface to our VMs, but it's not possible with already existing VMs on Google Cloud.
Google Cloud IPSec VPN – Managing Overlapping Subnetworks
google-cloud-platformgoogle-compute-enginenetworkingsite-to-site-vpn
Best Answer
You can setup Cloud VPN tunnel to GCP even if your on-prem ip address range (10.10.0.0/16) subset is overlapping with GCP vpc ip address range (10.10.0.0/24), based on guide [https://cloud.google.com/vpn/docs/concepts/order-of-routes#routing-examples].
But if your on-prem ip address range is subset of the GCP VPC ip address range, you cannot setup VPN at this situation, so you need either change your on-prem ip address range or GCP VPC's.
Current GCP doesn’t support adding additional network interface to existing VM. It can only be done during VM creation.