About the OpenShift SDN network plugin - OpenShift SDN network plugin | Networking

OpenShift SDN network isolation modes
Supported network plugin feature matrix

Part of Red Hat OpenShift Networking, OpenShift SDN is a network plugin that 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 OpenShift SDN, which configures an overlay network by using Open vSwitch (OVS).

For a cloud controller manager (CCM) with the --cloud-provider=external option set to cloud-provider-vsphere, a known issue exists for a cluster that operates in a networking environment with multiple subnets.

When you upgrade your cluster from OKD 4.12 to OKD 4.13, the CCM selects a wrong node IP address and this operation generates an error message in the namespaces/openshift-cloud-controller-manager/pods/vsphere-cloud-controller-manager logs. The error message indicates a mismatch with the node IP address and the vsphere-cloud-controller-manager pod IP address in your cluster.

The known issue might not impact the cluster upgrade operation, but you can set the correct IP address in both the nodeNetworking.external.networkSubnetCidr and the nodeNetworking.internal.networkSubnetCidr parameters for the nodeNetworking object that your cluster uses for its networking requirements.

OpenShift SDN network isolation modes

OpenShift SDN provides three SDN modes for configuring the pod network:

Network policy mode allows project administrators to configure their own isolation policies using NetworkPolicy objects. Network policy is the default mode in OKD 4.13.
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.
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 subnet mode.

Supported network plugin feature matrix

Red Hat OpenShift Networking offers two options for the network plugin, OpenShift SDN and OVN-Kubernetes, for the network plugin. The following table summarizes the current feature support for both network plugins:

Table 1. Default CNI network plugin feature comparison
Feature	OpenShift SDN	OVN-Kubernetes
egress IPs	Supported	Supported
egress firewall	Supported	Supported ^[1]
egress router	Supported	Supported ^[2]
Hybrid networking	Not supported	Supported
IPsec encryption for intra-cluster communication	Not supported	Supported
IPv4 single-stack	Supported	Supported
IPv6 single-stack	Not supported	Supported ^[3]
IPv4/IPv6 dual-stack	Not Supported	Supported ^[4]
IPv6/IPv4 dual-stack	Not supported	Supported ^[5]
Kubernetes network policy	Supported	Supported
Kubernetes network policy logs	Not supported	Supported
Hardware offloading	Not supported	Supported
Multicast	Supported	Supported

egress firewall is also known as egress network policy in OpenShift SDN. This is not the same as network policy egress.
egress router for OVN-Kubernetes supports only redirect mode.
IPv6 single-stack networking on a bare-metal platform.
IPv4/IPv6 dual-stack networking on bare-metal, VMware vSphere (installer-provisioned infrastructure installations only), IBM Power®, and IBM Z® platforms. On VMware vSphere, dual-stack networking limitations exist.
IPv6/IPv4 dual-stack networking on bare-metal and IBM Power® platforms.

Additional resources

For more information about dual-stack networking limitations on VMware vSphere, see Optional: Deploying with dual-stack networking.