Flannel - Container Networking Interface

Flannel is one of the most popular CNI plugins used and deployed in the wild given it's really straightforward and simple to setup

It's one of the simplest networking setup since all it does is create flat network - consisting a bunch of bridges and making pod-to-pod communication, inter-cluster, seemingless. Pods have unique IP addresses shared between the entire cluster. So 1 Pod should never have conflicting IP addresses, even thou it is deployed in different Nodes. Althought it makes possible for pod-to-pod, it can be a big performance bottleneck.

https://www.eficode.com/blog/debugging-kubernetes-networking

kubectl -n kube-system get configmap kube-flannel-cfg -o yaml