unable to access cluster after installing flannel

Question

I've got a cluster running with 1 master + 2 workers and using flannel as CNI.

kubeadm init was called with apiserver address and 10.244.0.0 for flannel's and nodes are joined.

kubeadm init --apiserver-advertise-address=192.168.56.3 --pod-network-cidr=10.244.0.0/16

NAME READY STATUS RESTARTS
coredns-f9fd979d6-d6jkd 1/1 Running 0
coredns-f9fd979d6-fpzct 1/1 Running 0
etcd-kubemaster 1/1 Running 0
kube-apiserver-kubemaster 1/1 Running 0
kube-controller-manager-kubemaster 1/1 Running 0
kube-flannel-ds-5gd2w 1/1 Running 0
kube-flannel-ds-b4qzz 1/1 Running 0
kube-flannel-ds-m56bd 1/1 Running 0
kube-proxy-5hw6x 1/1 Running 0
kube-proxy-9wnpd 1/1 Running 0
kube-proxy-ffrmh 1/1 Running 0
kube-scheduler-kubemaster 1/1 Running 0

iptables was cleared, everything allowed and net.bridge.bridge-nf-call-iptables=1

But the cluster cant be reached.

http://192.168.56.3:32001/

times out.

kubectl config view

apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: DATA+OMITTED
    server: https://192.168.56.3:6443
  name: kubernetes
contexts:
- context:
    cluster: kubernetes
    user: kubernetes-admin
  name: kubernetes-admin@kubernetes
current-context: kubernetes-admin@kubernetes
kind: Config
preferences: {}
users:
- name: kubernetes-admin
  user:
    client-certificate-data: REDACTED
    client-key-data: REDACTED

What to do to get access to the cluster's services?

Answer 1

It turns out that flannel itself must be initialized with the k8s interface.

kubectl get pod --all-namespaces | grep flannel

kube-system   kube-flannel-ds-2676q                 1/1     Running   0

kubectl logs kube-flannel-ds-5gd2w -n kube-system -f

I0603 05:56:36.014958       1 main.go:520] Determining IP address of default interface
I0603 05:56:36.015399       1 main.go:533] Using interface with name enp0s3 and address 10.0.2.15

enp0s3 is incorrect interface.

delete daemonset:

kubectl delete ds kube-flannel-ds -n kube-system

delete flannel.1 link:

ip link delete flannel.1

download kube-flannel

curl https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml -O

Add --iface arg to the kube-flannel with the interface that k8s is advertised on

• --iface=enp0s8

Apply it and k8s becomes accessible:

kubectl apply -f kube-flannel.yml

kubectl logs kube-flannel-ds-2676q -n kube-system -f
I0603 07:03:14.430280       1 main.go:533] Using interface with name enp0s8 and address 192.168.56.4

deleting the links is not necessary itself, flannel recreates it automatically

"flannel.1" already exists with incompatable configuration: vtep (external) interface: 3 vs 2; recreating device