CNI question

ryanbriley

I am a little confused about the role and boundaries of responsibilities of a CNI. In the course materials for chapter 4, it states that the CNI controls container to container networking within a given pod. However, the lab exercise for 3 describes cilium as a CNI.

My question is is cilium a CNI or an overlay or are those two concepts not mutually exclusive (ie. an overlay contains a CNI)?

Thanks in advance!

chrispokorni

Hi @ryanbriley,

The CNI standardizes the implementation and interaction between the Kubernetes framework and a CNI network plugin. Kubernetes cannot handle the Pod to Pod networking out of the box, or container communication, therefore it needs to rely on 3rd party network implementations, that implement the CNI requirements. Cilium is such a network plugin. These plugins are often called Pod network plugins, CNI plugins, CNI providers, etc. mostly for the sake of confusing the reader

Once a CNI plugin is installed, it defines an SDN (software defined network) layer that spans across all the nodes, connecting the Pods in your cluster and behaving as a DHCP server assigning IP addresses to Pods as they are created and launched.

Regards,
-Chris