Q: Kubeadm - unable to join nodes - request canceled while waiting for connection Trying to provision k8s cluster on 3 Debian 10 VMs with kubeadm.
All vms have 2 network interfaces, eth0 as public interface with static ip, eth1 as local interface with static ips in 192.168.0.0/16:

*

*Master: 192.168.1.1

*Node1: 192.168.2.1

*Node2: 192.168.2.2

All nodes have interconnect between them.
ip a from master host:
# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:52:70:53:d5:12 brd ff:ff:ff:ff:ff:ff
    inet XXX.XXX.244.240/24 brd XXX.XXX.244.255 scope global dynamic eth0
       valid_lft 257951sec preferred_lft 257951sec
    inet6 2a01:367:c1f2::112/48 scope global 
       valid_lft forever preferred_lft forever
    inet6 fe80::252:70ff:fe53:d512/64 scope link 
       valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:95:af:b0:8c:c4 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.1/16 brd 192.168.255.255 scope global eth1
       valid_lft forever preferred_lft forever
    inet6 fe80::295:afff:feb0:8cc4/64 scope link 
       valid_lft forever preferred_lft forever

Master node is initialized fine with:
kubeadm init --upload-certs --apiserver-advertise-address=192.168.1.1 --apiserver-cert-extra-sans=192.168.1.1,XXX.XXX.244.240 --pod-network-cidr=10.40.0.0/16 -v=5

Output
But when I join worker nodes kube-api is not reachable:
kubeadm join 192.168.1.1:6443 --token 7bl0in.s6o5kyqg27utklcl --discovery-token-ca-cert-hash sha256:7829b6c7580c0c0f66aa378c9f7e12433eb2d3b67858dd3900f7174ec99cda0e -v=5

Output
Netstat from master:
# netstat -tupn | grep :6443
tcp        0      0 192.168.1.1:43332       192.168.1.1:6443        TIME_WAIT   -                   
tcp        0      0 192.168.1.1:41774       192.168.1.1:6443        ESTABLISHED 5362/kube-proxy     
tcp        0      0 192.168.1.1:41744       192.168.1.1:6443        ESTABLISHED 5236/kubelet        
tcp        0      0 192.168.1.1:43376       192.168.1.1:6443        TIME_WAIT   -                   
tcp        0      0 192.168.1.1:43398       192.168.1.1:6443        TIME_WAIT   -                   
tcp        0      0 192.168.1.1:41652       192.168.1.1:6443        ESTABLISHED 4914/kube-scheduler 
tcp        0      0 192.168.1.1:43448       192.168.1.1:6443        TIME_WAIT   -                   
tcp        0      0 192.168.1.1:43328       192.168.1.1:6443        TIME_WAIT   -                   
tcp        0      0 192.168.1.1:43452       192.168.1.1:6443        TIME_WAIT   -                   
tcp        0      0 192.168.1.1:43386       192.168.1.1:6443        TIME_WAIT   -                   
tcp        0      0 192.168.1.1:43350       192.168.1.1:6443        TIME_WAIT   -                   
tcp        0      0 192.168.1.1:41758       192.168.1.1:6443        ESTABLISHED 5182/kube-controlle 
tcp        0      0 192.168.1.1:43306       192.168.1.1:6443        TIME_WAIT   -                   
tcp        0      0 192.168.1.1:43354       192.168.1.1:6443        TIME_WAIT   -                   
tcp        0      0 192.168.1.1:43296       192.168.1.1:6443        TIME_WAIT   -                   
tcp        0      0 192.168.1.1:43408       192.168.1.1:6443        TIME_WAIT   -                   
tcp        0      0 192.168.1.1:41730       192.168.1.1:6443        ESTABLISHED 5182/kube-controlle 
tcp        0      0 192.168.1.1:41738       192.168.1.1:6443        ESTABLISHED 4914/kube-scheduler 
tcp        0      0 192.168.1.1:43444       192.168.1.1:6443        TIME_WAIT   -                   
tcp6       0      0 192.168.1.1:6443        192.168.1.1:41730       ESTABLISHED 5094/kube-apiserver 
tcp6       0      0 192.168.1.1:6443        192.168.1.1:41744       ESTABLISHED 5094/kube-apiserver 
tcp6       0      0 192.168.1.1:6443        192.168.1.1:41738       ESTABLISHED 5094/kube-apiserver 
tcp6       0      0 192.168.1.1:6443        192.168.1.1:41652       ESTABLISHED 5094/kube-apiserver 
tcp6       0      0 ::1:6443                ::1:42862               ESTABLISHED 5094/kube-apiserver 
tcp6       0      0 192.168.1.1:6443        192.168.1.1:41758       ESTABLISHED 5094/kube-apiserver 
tcp6       0      0 ::1:42862               ::1:6443                ESTABLISHED 5094/kube-apiserver 
tcp6       0      0 192.168.1.1:6443        192.168.1.1:41774       ESTABLISHED 5094/kube-apiserver 

Pods from master:
# kubectl --kubeconfig=/etc/kubernetes/admin.conf get pods -n kube-system -o wide
NAME                                              READY   STATUS    RESTARTS   AGE   IP                   NODE                      NOMINATED NODE   READINESS GATES
coredns-558bd4d5db-8qhhl                          0/1     Pending   0          12m   <none>               <none>                    <none>           <none>
coredns-558bd4d5db-9hj7z                          0/1     Pending   0          12m   <none>               <none>                    <none>           <none>
etcd-cloud604486.fastpipe.io                      1/1     Running   0          12m   2a01:367:c1f2::112   cloud604486.fastpipe.io   <none>           <none>
kube-apiserver-cloud604486.fastpipe.io            1/1     Running   0          12m   2a01:367:c1f2::112   cloud604486.fastpipe.io   <none>           <none>
kube-controller-manager-cloud604486.fastpipe.io   1/1     Running   0          12m   2a01:367:c1f2::112   cloud604486.fastpipe.io   <none>           <none>
kube-proxy-dzd42                                  1/1     Running   0          12m   2a01:367:c1f2::112   cloud604486.fastpipe.io   <none>           <none>
kube-scheduler-cloud604486.fastpipe.io            1/1     Running   0          12m   2a01:367:c1f2::112   cloud604486.fastpipe.io   <none>           <none>

All vms have this kernel parameters set:

*

*{ name: 'vm.swappiness', value: '0' }

*{ name: 'net.bridge.bridge-nf-call-iptables', value: '1' }

*{ name: 'net.bridge.bridge-nf-call-ip6tables', value: '1'}

*{ name: 'net.ipv4.ip_forward', value: 1 }

*{ name: 'net.ipv6.conf.all.forwarding', value: 1}
br_netfilter kernel module active and iptables set to legacy mode (via alternatives)
Am I missing something?

A: After 1 week of tinkering issue boiled down to a service provider network miscounfiguration.
For anyone having this same issue check the MTU of your network, in my case it defaulted to 1500 instead of recommended 1450.
