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I'm running kubernetes with the supposed pod network cidr of 10.244.0.0/16. Everything seems to agree with that:

# history | grep kubeadm
kubeadm init --control-plane-endpoint "guide:6443" --upload-certs --pod-network-cidr=10.244.0.0/16

$ kubectl get nodes -o kubectl get nodes -o jsonpath='{.items[*].spec.podCIDR}'
10.244.0.0/24 10.244.1.0/24 10.244.2.0/24 10.244.3.0/24 10.244.4.0/24 10.244.5.0/24

# cat /run/flannel/subnet.env 
FLANNEL_NETWORK=10.244.0.0/16
FLANNEL_SUBNET=10.244.0.1/24
FLANNEL_MTU=1450
FLANNEL_IPMASQ=true

However all the pods I create get IPs in the 172.17.0.0/16 range.

$ kubectl get pods -o wide
NAME                                   READY   STATUS             RESTARTS   AGE   IP            NODE         NOMINATED NODE   READINESS GATES
busybox1                               1/1     Running            1          13m   172.17.0.11   k8s-node-1   <none>           <none>
debain-shell-547f8fc54b-v8p99          0/1     ImagePullBackOff   0          27m   172.17.0.3    k8s-node-1   <none>           <none>
nginx-deployment-ex-54f57cf6bf-k55nn   1/1     Running            1          27m   172.17.0.5    k8s-node-1   <none>           <none>
nginx-deployment-ex-54f57cf6bf-q2khx   1/1     Running            1          27m   172.17.0.9    k8s-node-1   <none>           <none>
nginx-deployment-ex-54f57cf6bf-r8b7v   1/1     Running            1          27m   172.17.0.7    k8s-node-1   <none>           <none>

I can't talk to coredns (which is how I found this condition) and I can't seem to use my ingress service anymore (though I've restarted enough things by now I may have just temporarily broken that).

What is causing this, or alternatively, where should I look for more info?

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1 Answer 1

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2

This was caused by missing --network-plugin=cni on the end of kubelet. Added that to the args and it all works now.

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  • Hello Alex. I am facing exactly same issue in my cluster. Same range of unexpected CIDR is used for IP allocation. Can you share some detail how did you pass --network-plugin=cni in kubelet. I install kubelet by apt-get install kubelet. I am new to kubernetes. Thanks in advance.
    – Mufazzal
    Commented May 21, 2022 at 6:49
  • Sorry, I don't check my account often. I'm on gentoo and there it's in the /etc/conf.d/kubelet file. However I'm pretty sure it's not going to be the same on a debian based distro, sorry (esp to anyone else who comes across this).
    – Alex Orange
    Commented Oct 26, 2023 at 20:47

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