I am trying to setup k8s cluster with master and two worker nodes in Digital Ocean.

My Config: I have created three droplets as follows:

1. Master: 2cpu, 3GB Mem
2. Worker Node1: 1cpu, 2GB Mem
3. Worker Node2: 1cpu, 2GB Mem

I was able to setup master node successfully

$ kubectl get nodes
NAME                         STATUS   ROLES    AGE    VERSION
master                       Ready    master   139m   v1.18.3

I am unable to add worker to master.

Command i ran to join:

$ kubeadm join <PUBLIC IP>:6443 --token <token> --discovery-token-ca-cert-hash <hash>

Token had 23h of validity left at the time of executing the above command.

Error that i got:

W0528 14:13:09.920404 25129 join.go:346] [preflight] WARNING: JoinControlPane.controlPlane settings will be ignored when control-plane flag is not set.

[preflight] Running pre-flight checks error execution phase preflight: couldn't validate the identity of the API Server: Get https://PUBLIC_IP:6443/api/v1/namespaces/kube-public/configmaps/cluster-info?timeout=10s: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers) To see the stack trace of this error execute with --v=5 or higher

My observations on this issue:

$ netstat -pnltu
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 127.0.0.1:40389         0.0.0.0:*               LISTEN      25074/kubelet       
tcp        0      0 127.0.0.1:10248         0.0.0.0:*               LISTEN      25074/kubelet       
tcp        0      0 127.0.0.1:10249         0.0.0.0:*               LISTEN      25478/kube-proxy 
tcp        0      0 127.0.0.1:9099          0.0.0.0:*               LISTEN      29823/calico-node
tcp        0      0 127.0.0.1:10257         0.0.0.0:*               LISTEN      24580/kube-controll 
tcp        0      0 127.0.0.1:10259         0.0.0.0:*               LISTEN      24742/kube-schedule
tcp6       0      0 :::10250                :::*                    LISTEN      25074/kubelet       
tcp6       0      0 :::10251                :::*                    LISTEN      24742/kube-schedule 
tcp6       0      0 :::6443                 :::*                    LISTEN      24725/kube-apiserve 
tcp6       0      0 :::10252                :::*                    LISTEN      24580/kube-controll 
tcp6       0      0 :::10256                :::*                    LISTEN      25478/kube-proxy 

Is it because the API service is listening in IPV6 instead of IPV4?

here is the output of cluster-info:

$ kubectl cluster-info
Kubernetes master is running at https://<PUBLIC_IP>:6443
KubeDNS is running at https://<PUBLIC_IP>:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

Any help to fix this issue is much appreciated.