Use Calico instead of Flannel

Network Policies

k3s comes with a controller that enforces network policies by default. You do not need to switch to Calico for network policies to be enforced. See https://github.com/k3s-io/k3s/issues/1308 for more information.
The docs below assume you want to switch to Calico’s policy engine, thus setting --disable-network-policy.

1. Download and modify the Calico descriptor

You can following the documentation

And then you have to change the ConfigMap calico-config. On the cni_network_config add the entry for allowing IP forwarding

"container_settings": {
    "allow_ip_forwarding": true
}

Or you can directly use this calico.yaml manifest

2. Create the cluster without flannel and with calico

On the k3s cluster creation :

• add the flags --flannel-backend=none and --disable-network-policy. For this, on k3d you need to forward this flag to k3s with the option --k3s-arg.
• mount (--volume) the calico descriptor in the auto deploy manifest directory of k3s /var/lib/rancher/k3s/server/manifests/

So the command of the cluster creation is (when you are at root of the k3d repository)

k3d cluster create "${clustername}" \
  --k3s-arg '--flannel-backend=none@server:*' \
  --k3s-arg '--disable-network-policy' \
  --volume "$(pwd)/docs/usage/guides/calico.yaml:/var/lib/rancher/k3s/server/manifests/calico.yaml"

In this example :

• change "${clustername}" with the name of the cluster (or set a variable).
• $(pwd)/docs/usage/guides/calico.yaml is the absolute path of the calico manifest, you can adapt it.

You can add other options, see.

The cluster will start without flannel and with Calico as CNI Plugin.

For watching for the pod(s) deployment

watch "kubectl get pods -n kube-system"    

You will have something like this at beginning (with the command line kubectl get pods -n kube-system)

NAME                                       READY   STATUS     RESTARTS   AGE
helm-install-traefik-pn84f                 0/1     Pending    0          3s
calico-node-97rx8                          0/1     Init:0/3   0          3s
metrics-server-7566d596c8-hwnqq            0/1     Pending    0          2s
calico-kube-controllers-58b656d69f-2z7cn   0/1     Pending    0          2s
local-path-provisioner-6d59f47c7-rmswg     0/1     Pending    0          2s
coredns-8655855d6-cxtnr                    0/1     Pending    0          2s

And when it finish to start

NAME                                       READY   STATUS      RESTARTS   AGE
metrics-server-7566d596c8-hwnqq            1/1     Running     0          56s
calico-node-97rx8                          1/1     Running     0          57s
helm-install-traefik-pn84f                 0/1     Completed   1          57s
svclb-traefik-lmjr5                        2/2     Running     0          28s
calico-kube-controllers-58b656d69f-2z7cn   1/1     Running     0          56s
local-path-provisioner-6d59f47c7-rmswg     1/1     Running     0          56s
traefik-758cd5fc85-x8p57                   1/1     Running     0          28s
coredns-8655855d6-cxtnr                    1/1     Running     0          56s

Note :

• you can use the auto deploy manifest or a kubectl apply depending on your needs
• Calico is not as quick as Flannel (but it provides more features)

References

• https://rancher.com/docs/k3s/latest/en/installation/network-options/
• https://docs.projectcalico.org/getting-started/kubernetes/k3s/

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Last update: June 7, 2022