无法在IPv4上访问Kubernetes服务

Question

we currently have following Kubernetes setup (v1.13.1, setup with kubeadm ) with connectivity set up between them:

• Master node (bare metal)
• 5 worker nodes (bare metal)
• 2 worker nodes (cloud)
• There is no proxy in between to access cluster, currently we are accessing services via hostname:NodePort

We are experiencing issue with accessing services via NodePort on 2 cloud worker nodes. What is happening is that service is accessible via IPv6, but not via IPv4:

• IPv6: telnet localhost6 30005 Trying ::1... Connected to localhost6. Escape character is '^]'.
• IPv4: telnet localhost4 30005 Trying 127.0.0.1...

Thing is that both are working on bare metal nodes. If I use netstat -napl | grep 30005 netstat -napl | grep 30005 , I can see kube-proxy is listening on this port ( tcp6 ). I presumed this means that it does not listen on tcp , but aparently this is not the case (I have same picture on bare metal worker nodes):

tcp6       7      0 :::30005                :::*                    LISTEN      24658/kube-proxy

I have also read that services are using IPv6, but based on bare metal worker nodes, it seems there should not be a problem using IPv4 there as well.

Any idea what would cause that issue and how to solve it?

Thank you and best regards, Bostjan

Answer 1

In case someone stumbles upon same issue, there was issue with unopened ports on FW for flannel network overlay:

• 8285 UDP - flannel UDP backend
• 8472 UDP - flannel vxlan backend