Understanding the Kubernetes networking model

The Kubernetes networking model is based on a flat address space. All pods in a cluster can directly see each other. Each pod has its own IP address. There is no need to configure any NAT. In addition, containers in the same pod share their pod's IP address and can communicate with each other through localhost. This model is pretty opinionated, but once set up, it simplifies life considerably both for developers and administrators. It makes it particularly easy to migrate traditional network applications to Kubernetes. A pod represents a traditional node and each container represents a traditional process.

Intra-pod communication (container to container)

A running pod is always scheduled on one (physical or virtual) node. That means that all the containers run on the same node and can talk to each other in various ways, such as the local filesystem, any IPC mechanism, or using localhost and well-known ports. There is no danger of port collision...