OKD uses a software-defined networking (SDN) approach to provide a unified cluster network that enables communication between Pods across the OKD cluster. This Pod network is established and maintained by the OpenShift SDN, which configures an overlay network using Open vSwitch (OVS).
OpenShift SDN provides three SDN modes for configuring the Pod network:
The network policy mode allows project administrators to configure their own isolation policies using NetworkPolicy objects. Network policy is the default mode in OKD Latest.
The multitenant mode provides project-level isolation for Pods and Services. Pods from different projects cannot send packets to or receive packets from Pods and Services of a different project. You can disable isolation for a project, allowing it to send network traffic to all Pods and Services in the entire cluster and receive network traffic from those Pods and Services.
The subnet mode provides a flat Pod network where every Pod can communicate with every other Pod and Service. The network policy mode provides the same functionality as the subnet mode.