If you need to have 2 different vpc-s (from same or a different account) to be able communicate, you need to make sure that their subnets do not overlap otherwise the you will not be able to set up the route tables. General approach is to:

• Create the peering connection between the 2 subnets
• Create the routes in both VPCs for the respective subnets with the peering connection as a gateway
• Make sure the security groups allow traffic from one subnet to the other

For k8s cluster vpc connections to test it, you can run a pod and try to ping/curl some resource you want to access in another vpc:

kubectl --kubeconfig=test-kubeconfig run test-pod --image=busybox --restart=Never --rm -it -- /bin/sh ping 10.10.10.15

The address 10.10.10.15 is some resource in the second VPC.

• aws troubleshooting

• https://docs.aws.amazon.com/vpc/latest/peering/troubleshoot-vpc-peering-connections.html