Network Design Principles
Source: https://kubernetes.io/docs/concepts/cluster-administration/networking/#kubernetes-ip-address-ranges
Node Network
The Node Network consists of Kubernetes worker nodes and control plane nodes. All nodes can communicate with each other.
Every node in the Kubernetes cluster should be able to communicate with every other node without NAT (Network Address Translation).
Kubernetes assumes a flat network where all nodes can talk freely.
Nodes usually have a routable IP address within the cluster.
To see Nodes IP we can use command kubectl get nodes -o wide.
➜ kubectl get nodes -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP
minikube Ready control-plane 19h v1.31.0 192.168.49.2
EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
<none> Ubuntu 22.04.4 LTS 6.10.14-linuxkit docker://27.2.0Pod Network
The Pod Network is where all Kubernetes pods communicate. Pods within the cluster communicate using direct IP routing.
Every pod gets a unique IP Address.
Every pod in a Kubernetes cluster gets a unique IP address.
Pod-to-pod communication happens directly without NAT.
The Container Network Interface (CNI) plugin is responsible for managing pod networking.
Container inside the same pod communicate by
localhost.
We can test pod to pod communication by ping from a pod to other pod.
➜ kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE
postgres-f8f589d5b-59rw8 1/1 Running 0 4h37m
simple-go-5dc4557ffc-c24fp 1/1 Running 0 4h8m
simple-go-5dc4557ffc-d6tz6 1/1 Running 0 4h8m
simple-go-5dc4557ffc-gv4fv 1/1 Running 0 4h8m
IP NODE NOMINATED NODE READINESS GATES
10.244.0.11 minikube <none> <none>
10.244.0.17 minikube <none> <none>
10.244.0.15 minikube <none> <none>
10.244.0.16 minikube <none> <none>➜ kubectl exec -it simple-go-5dc4557ffc-c24fp -- ping 10.244.0.11
PING 10.244.0.11 (10.244.0.11): 56 data bytes
64 bytes from 10.244.0.11: seq=0 ttl=64 time=97.104 ms
64 bytes from 10.244.0.11: seq=1 ttl=64 time=0.219 ms
64 bytes from 10.244.0.11: seq=2 ttl=64 time=0.292 ms
64 bytes from 10.244.0.11: seq=3 ttl=64 time=0.160 ms
64 bytes from 10.244.0.11: seq=4 ttl=64 time=0.395 ms
^C
--- 10.244.0.11 ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max = 0.160/19.634/97.104 msService Network
The Service Network is a virtual network used for Kubernetes Services. Services get a stable ClusterIP that does not change. Kubernetes load-balances traffic across backend pods.
Kubernetes rewrites outbound traffic from a pod if it's destined for a Service.This ensures that the request is routed correctly to a backend pod.
Services use ClusterIP (virtual IP) to route traffic to pods.
kube-proxy manages service traffic using iptables or IPVS.
Get service endpoints:
➜ kubectl get endpoints
NAME ENDPOINTS AGE
kubernetes 192.168.49.2:8443 24h
postgres 10.244.0.11:5432 4h35m
simple-go 10.244.0.15:8080,10.244.0.16:8080,10.244.0.17:8080 4h11mReferences
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