KodeCloud Kubernetes Networking

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Networking¶

In Docker an IP address is assigned to a container whereas in k8s IP address is always assigned to a pod.

When k8s is initially configured an internal private network is configured with the address range of 10.244.0.0 and all the pods are attached to it.
- When we deploy multiple pods they are assigned a specific IP address from this address.
- The pods can communicate each other through this IP.
  - Not the ideal way of establishing communication since the IP addresses can change when pods are recreated.
How does networking work in a cluster (multiple nodes)?
From the above example if we have 2 nodes which are not a part of a cluster they will have the same IP address range.
- This isn't going to work
When a k8s cluster is setup it doesn't automatically setup a network to handle networking.
K8s expects us to setup networking to meet certain requirements.
- Kubernetes dictates the networking requirements and it is the responsibility of CNI (plugins) to ensure that these requirements are met.
These requirements are:
- All containers/PODs can communicate to one another WITHOUT NAT.
- All nodes can communicate with all containers and vice-versa WITHOUT NAT.
Some CNI plugins are:
Once setup they are responsible for managing the networking.
- It assigns different network address for each network in the node thereby creating a virtual network.
- Notice that different nodes have different network ranges.
Different ways of accessing the pod inside k8s cluster
- SSH into the worker node
- Using a node port service:

Last updated: 2023-05-16