kubernetes-networking-networking-and-pod-to-pod-communication

Networking and Pod to Pod Communication

Networking is crucial for communication between pods and resources in a Kubernetes cluster. Each pod has a unique IP address and can communicate with other pods directly. Container networking interface (CNI) plugins are used to configure pod network interfaces and provide isolation between pods. Kubernetes also provides networking services such as load balancing, service discovery, and ingress, which enable external traffic to access pods and services. These services are implemented using Kubernetes objects such as Services, Ingress, and NetworkPolicies. Networking and pod-to-pod communication are essential for scalability, reliability, and flexibility in Kubernetes clusters.

Learn more from the following resources:

Network Policies in Kubernetes

Default Behavior (No Network Policies)

By default, all pods are non-isolated
All ingress (incoming) traffic is allowed
All egress (outgoing) traffic is allowed

With Network Policies

Policies can restrict both ingress and egress traffic
Pod A (Source) has egress policies defining:

Which namespaces it can send to
Which IP ranges it can connect to

Pod B (Destination) has ingress policies defining:

Which namespaces can connect to it
Which pods (by label) can connect to it

Special Cases

Node traffic is always allowed (to/from the node where pod is running)
Pods cannot block access to themselves
Policies are additive (combine with OR logic)

Policy Evaluation

For a connection to be allowed:
- Source pod’s egress policy must allow it AND
- Destination pod’s ingress policy must allow it
If either policy blocks the connection, it won’t be allowed

Policy Selectors can be based on

Pod labels
Namespace labels
IP blocks (CIDR ranges)

kubernetes-networking-networking-and-pod-to-pod-communication

Contents

Networking and Pod to Pod Communication

Network Policies in Kubernetes