How to: Is it possible to route traffic from outside the Kubernetes cluster directly to pods?
Yes. But one major downside of that is that ClusterIPs are implemented as iptables rules on cluster clients, so you'd lose the ability to see Cluster IPs and service changes. Because the iptables are managed by kube-proxy you could do this by running a kube-proxy, which is similar to just joining the cluster. You could make all your services Headless(ClusterIP = None), this would give your external servers the ability to talk directly to services if they could use the kubernetes dns. Headless services don't use ClusterIPs, but instead just create a DNS A record for all pods in the service. kube-dns is run inside the cluster as a ClusterIP, so there's a chicken and egg problem with DNS you would have to deal with.