networking
things to know:
pods
- k8s handles networking at pod level (so k8s doesn’t connect containers but pods to each other)
- each pod gets its own ip address on the cluster, run
k get pods --all-namespaces -o wide, k8s has a pool of IPs from which it allocated IPs! - by default pods can connect to all pods on all nodes, but there are ways of limiting this using the networking policies which can get very granular
- containers in pods can communicate with each other through localhost, as a pod can have multiple containers running at the same time!
cni plugin - the tool to help k8s do all the n/w ing
- container networking interface plugin
- provides n/w connectivity to containers in the cluster
- configures network interfaces in containers
- assigns ip addresses and sets up routes → iptables on nodes
- when we setup a cluster from scratch we often have to choose a cni plugin:
- Cilium
- Calico
- Flannel - rancher desktop uses this as its CNI plugin!
Note:
to checkout we can use the rdctl shell command to enter into the rancher desktop VM that runs the cluster and we can navigate to /etc/cni to checkout the CNI plugin.
checkout k8s services
Links:
202508311241