In this network topology, two clusters have their own instance of ASM control plane and are part of the same VPC. There is direct connectivity between services in the mesh across clusters. Both the clusters must be setup to trust each other. This can be achieved by exchanging secrets (certificate derived from common root CA) of the other cluster thereby enabling access to Kubernetes (GKE) API servers. In effect, cluster one will be able to access
API server and discover endpoints of the second cluster and vice versa. Following figure shows the topology for this setup.
As both the clusters are part of same VPC, there is no need of routing via ingress gateway. Service endpoints in both the clusters can directly communicate with each other.