Switching from Flannel to Cillium - what's the procedure?

[aidas-emersoft]

I would like to utilise more advanced Network Policy features that are only available in Cilium, however my K3s clusters are provisioned with Flannel. What would be the procedure to upgrade that? Would changing CNI in cluster_config.yaml from flannel to cilium simply work? Thanks.

[vitobotta]

Hi, k3s comes out of the box with a Network Policy Controller based on kube-router that handles network policies. Have you tried that? It's not clear from your question.

[aidas-emersoft]

Yes, I use them a lot! But I would also like to use CiliumNetworkPolicy CRD where I can specify particular FQDNs for the egress.

[vitobotta]

Gotcha. I have heard some time ago of someone who migrated from Flannel to Cilium, but I have never tried it myself and it surely requires significant downtime. Of course, you need to switch to Cilium to do what you want.