Cluster to Cluster communication

Dear Team,

Kindly help understand how the cluster to cluster communication can be enabled for the critical prod environment. Cluster one running / configured with legacy RKE with Kubernate v1.19 / Docker v1.10 without isiio however the other cluster configured and running with RKE1 with Kubernate v1.26 and Docker 1.20.x. So kindly advise LB between cluster can be mapped with worker node on other side to forward the traffic with specific port is suggestable in turns of security, etc., as the NodePort as service type can also be part of plan.

So please suggest on this…

Regards