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Networking overview

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OpenShift Virtualization provides advanced networking functionality by using custom resources and plugins. Virtual machines (VMs) are integrated with Red Hat OpenShift Service on AWS networking and its ecosystem.

You cannot run OpenShift Virtualization on a single-stack IPv6 cluster.

The following figure illustrates the typical network setup of OpenShift Virtualization. Other configurations are also possible.

OpenShift Virtualization networking architecture
Figure 1. OpenShift Virtualization networking overview

20 Pods and VMs run on the same network infrastructure which allows you to easily connect your containerized and virtualized workloads.

20 You can connect VMs to the default pod network and to any number of secondary networks.

20 The default pod network provides connectivity between all its members, service abstraction, IP management, micro segmentation, and other functionality.

20 Multus is a "meta" CNI plugin that enables a pod or virtual machine to connect to additional network interfaces by using other compatible CNI plugins.

20 The default pod network is overlay-based, tunneled through the underlying machine network.

20 The machine network can be defined over a selected set of network interface controllers (NICs).

20 Secondary VM networks are typically bridged directly to a physical network, with or without VLAN encapsulation. It is also possible to create virtual overlay networks for secondary networks.

Connecting VMs directly to the underlay network is not supported on Red Hat OpenShift Service on AWS.

20 Secondary VM networks can be defined on dedicated set of NICs, as shown in Figure 1, or they can use the machine network.

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OpenShift Virtualization networking glossary

The following terms are used throughout OpenShift Virtualization documentation:

Container Network Interface (CNI)

A Cloud Native Computing Foundation project, focused on container network connectivity. OpenShift Virtualization uses CNI plugins to build upon the basic Kubernetes networking functionality.

Multus

A "meta" CNI plugin that allows multiple CNIs to exist so that a pod or virtual machine can use the interfaces it needs.

Custom resource definition (CRD)

A Kubernetes API resource that allows you to define custom resources, or an object defined by using the CRD API resource.

Network attachment definition (NAD)

A CRD introduced by the Multus project that allows you to attach pods, virtual machines, and virtual machine instances to one or more networks.

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Using the default pod network

Connecting a virtual machine to the default pod network

Each VM is connected by default to the default internal pod network. You can add or remove network interfaces by editing the VM specification.

Exposing a virtual machine as a service

You can expose a VM within the cluster or outside the cluster by creating a Service object.

Configuring VM secondary network interfaces

You can connect a virtual machine to a secondary network by using an OVN-Kubernetes Container Network Interface (CNI) plugin. It is not required to specify the primary pod network in the VM specification when connecting to a secondary network interface.

Connecting a virtual machine to an OVN-Kubernetes secondary network

You can connect a VM to an Open Virtual Network (OVN)-Kubernetes secondary network. OpenShift Virtualization supports the layer2 topology for OVN-Kubernetes.

A layer2 topology connects workloads by a cluster-wide logical switch. The OVN-Kubernetes CNI plugin uses the Geneve (Generic Network Virtualization Encapsulation) protocol to create an overlay network between nodes. You can use this overlay network to connect VMs on different nodes, without having to configure any additional physical networking infrastructure.

To configure an OVN-Kubernetes secondary network and attach a VM to that network, perform the following steps:

  1. Configure an OVN-Kubernetes secondary network by creating a network attachment definition (NAD).

  2. Connect the VM to the OVN-Kubernetes secondary network by adding the network details to the VM specification.

Hot plugging secondary network interfaces

You can add or remove secondary network interfaces without stopping your VM. OpenShift Virtualization supports hot plugging and hot unplugging for secondary interfaces that use bridge binding and the OVN-Kubernetes layer2 topology.

Configuring and viewing IP addresses

You can configure an IP address of a secondary network interface when you create a VM. The IP address is provisioned with cloud-init. You can view the IP address of a VM by using the Red Hat OpenShift Service on AWS web console or the command line. The network information is collected by the QEMU guest agent.

Integrating with OpenShift Service Mesh

Connecting a virtual machine to a service mesh

OpenShift Virtualization is integrated with OpenShift Service Mesh. You can monitor, visualize, and control traffic between pods and virtual machines.

Managing MAC address pools

Managing MAC address pools for network interfaces

The KubeMacPool component allocates MAC addresses for VM network interfaces from a shared MAC address pool. This ensures that each network interface is assigned a unique MAC address. A virtual machine instance created from that VM retains the assigned MAC address across reboots.

Configuring SSH access

Configuring SSH access to virtual machines

You can configure SSH access to VMs by using the following methods:

  • virtctl ssh command

    You create an SSH key pair, add the public key to a VM, and connect to the VM by running the virtctl ssh command with the private key.

    You can add public SSH keys to Red Hat Enterprise Linux (RHEL) 9 VMs at runtime or at first boot to VMs with guest operating systems that can be configured by using a cloud-init data source.

  • virtctl port-forward command

    You add the virtctl port-foward command to your .ssh/config file and connect to the VM by using OpenSSH.

  • Service

    You create a service, associate the service with the VM, and connect to the IP address and port exposed by the service.

  • Secondary network

    You configure a secondary network, attach a VM to the secondary network interface, and connect to its allocated IP address.