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Chapter 18. Multiple networks

18.1. Understanding multiple networks

By default, OVN-Kubernetes serves as the Container Network Interface (CNI) of an OpenShift Container Platform cluster. With OVN-Kubernetes as the default CNI of a cluster, OpenShift Container Platform administrators or users can leverage user-defined networks (UDNs) or NetworkAttachmentDefinition (NADs) to create one, or multiple, default networks that handle all ordinary network traffic of the cluster. Both user-defined networks and Network Attachment Definitions can serve as the following network types:

  • Primary networks: Act as the primary network for the pod. By default, all traffic passes through the primary network unless a pod route is configured to send traffic through other networks.
  • Secondary networks: Act as additional, non-default networks for a pod. Secondary networks provide separate interfaces dedicated to specific traffic types or purposes. Only pod traffic that is explicitly configured to use a secondary network is routed through its interface.

However, during cluster installation, OpenShift Container Platform administrators can configure alternative default secondary pod networks by leveraging the Multus CNI plugin. With Multus, multiple CNI plugins such as ipvlan, macvlan, or Network Attachment Definitions can be used together to serve as secondary networks for pods.

Note

User-defined networks are only available when OVN-Kubernetes is used as the CNI. They are not supported for use with other CNIs.

You can define an additional network based on the available CNI plugins and attach one or more of these networks to your pods. You can define more than one additional network for your cluster depending on your needs. This gives you flexibility when you configure pods that deliver network functionality, such as switching or routing.

For a complete list of supported CNI plugins, see "Additional networks in OpenShift Container Platform".

For information about user-defined networks, see About user-defined networks (UDNs).

For information about Network Attachment Definitions, see Creating primary networks using a NetworkAttachmentDefinition.

18.1.1. Usage scenarios for an additional network

You can use an additional network in situations where network isolation is needed, including data plane and control plane separation. Isolating network traffic is useful for the following performance and security reasons:

  1. Performance

    Traffic management: You can send traffic on two different planes to manage how much traffic is along each plane.

  2. Security

    Network isolation: You can send sensitive traffic onto a network plane that is managed specifically for security considerations, and you can separate private data that must not be shared between tenants or customers.

All of the pods in the cluster still use the cluster-wide default network to maintain connectivity across the cluster. Every pod has an eth0 interface that is attached to the cluster-wide pod network. You can view the interfaces for a pod by using the oc exec -it <pod_name> -- ip a command. If you add additional network interfaces that use Multus CNI, they are named net1, net2, …​, netN.

To attach additional network interfaces to a pod, you must create configurations that define how the interfaces are attached. You specify each interface by using either a UserDefinedNetwork custom resource (CR) or a NetworkAttachmentDefinition CR. A CNI configuration inside each of these CRs defines how that interface is created.

For more information about creating a UserDefinedNetwork CR, see About user-defined networks.

For more information about creating a NetworkAttachmentDefinition CR, see Creating primary networks using a NetworkAttachmentDefinition.

18.1.2. Additional networks in OpenShift Container Platform

OpenShift Container Platform provides the following CNI plugins for creating additional networks in your cluster:

18.2. Primary networks

18.2.1. About user-defined networks

Important

UserDefinedNetwork is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see Technology Preview Features Support Scope.

Before the implementation of user-defined networks (UDN), the OVN-Kubernetes CNI plugin only supported a Layer 3 topology on the primary, or main, network that all pods are attached to. This allowed for network models where all pods in the cluster were part of the same global Layer 3 network, but restricted the ability to customize primary network configurations.

User-defined networks provide cluster administrators and users with highly customizable network configuration options for both primary and secondary network types. With UDNs, administrators can create tailored network topologies with enhanced isolation, IP address management for workloads, and advanced networking features. Supporting both Layer 2 and Layer 3 topology types, UDNs enable a wide range of network architectures and topologies, enhancing network flexibility, security, and performance.

Note
  • Support for the Localnet topology on both primary and secondary networks will be added in a future version of OpenShift Container Platform.

Unlike NADs, which are only namespaced scope, UDNs offer administrators the ability to create and define additional networks spanning multiple namespaces at the cluster level by leveraging the ClusterUserDefinedNetwork custom resource (CR). UDNs also offer both administrators and users the ability to define additional networks at the namespace level with the UserDefinedNetwork CR.

The following sections further emphasize the benefits and limitations of user-defined networks, the best practices when creating a ClusterUserDefinedNetwork or UserDefinedNetwork custom resource, how to create the custom resource, and additional configuration details that might be relevant to your deployment.

18.2.1.1. Benefits of a user-defined network

User-defined networks provide the following benefits:

  1. Enhanced network isolation for security

    • Tenant isolation: Namespaces can have their own isolated primary network, similar to how tenants are isolated in Red Hat OpenStack Platform (RHOSP). This improves security by reducing the risk of cross-tenant traffic.

  2. Network flexibility

    • Layer 2 and layer 3 support: Cluster administrators can configure primary networks as layer 2 or layer 3 network types. This provides the flexibility of a secondary network to the primary network.

  3. Simplified network management

    • Reduced network configuration complexity: With user-defined networks, the need for complex network policies are eliminated because isolation can be achieved by grouping workloads in different networks.

  4. Advanced capabilities

    • Consistent and selectable IP addressing: Users can specify and reuse IP subnets across different namespaces and clusters, providing a consistent networking environment.
    • Support for multiple networks: The user-defined networking feature allows administrators to connect multiple namespaces to a single network, or to create distinct networks for different sets of namespaces.

  5. Simplification of application migration from Red Hat OpenStack Platform (RHOSP)

    • Network parity: With user-defined networking, the migration of applications from OpenStack to OpenShift Container Platform is simplified by providing similar network isolation and configuration options.

Developers and administrators can create a user-defined network that is namespace scoped using the custom resource. An overview of the process is: create a namespace, create and configure the custom resource, create pods in the namespace.

18.2.1.2. Limitations for UserDefinedNetwork custom resource

While user-defined networks (UDN) offer highly customizable network configuration options, there are limitations that cluster administrators and developers should be aware of when implementing and managing these networks. Consider the following limitations before implementing a user-defined network.

  • DNS limitations:

    • DNS lookups for pods resolve to the pod’s IP address on the cluster default network. Even if a pod is part of a user-defined network, DNS lookups will not resolve to the pod’s IP address on that user-defined network. However, DNS lookups for services and external entities will function as expected.
    • When a pod is assigned to a primary UDN, it can access the Kubernetes API (KAPI) and DNS services on the cluster’s default network.
  • Initial network assignment: You must create the namespace and network before creating pods. Assigning a namespace with pods to a new network or creating a UDN in an existing namespace will not be accepted by OVN-Kubernetes.
  • Health check limitations: Kubelet health checks are performed by the cluster default network, which does not confirm the network connectivity of the primary interface on the pod. Consequently, scenarios where a pod appears healthy by the default network, but has broken connectivity on the primary interface, are possible with user-defined networks.
  • Network policy limitations: Network policies that enable traffic between namespaces connected to different user-defined primary networks are not effective. These traffic policies do not take effect because there is no connectivity between these isolated networks.

18.2.1.3. Best practices for UserDefinedNetwork

Before setting up a UserDefinedNetwork (UDN) resource, users should consider the following information:

  • openshift-* namespaces should not be used to set up a UDN.

  • 2 masquerade IP addresses are required for user defined networks. You must reconfigure your masquerade subnet to be large enough to hold the required number of networks.

    Important
    • For OpenShift Container Platform 4.17 and later, clusters use 169.254.0.0/17 for IPv4 and fd69::/112 for IPv6 as the default masquerade subnet. These ranges should be avoided by users. For updated clusters, there is no change to the default masquerade subnet.
    • Changing the cluster’s masquerade subnet is unsupported after a user-defined network has been configured for a project. Attempting to modify the masquerade subnet after a UDN has been set up can disrupt the network connectivity and cause configuration issues.
  • Ensure tenants are using the UserDefinedNetwork resource and not the NetworkAttachmentDefinition (NAD) resource. This can create security risks between tenants.
  • When creating network segmentation, you should only use the NAD resource if user-defined network segmentation cannot be completed using the UDN resource.
  • The cluster subnet and services CIDR for a UDN cannot overlap with the default cluster subnet CIDR. OVN-Kubernetes network plugin uses 100.64.0.0/16 as the default network’s join subnet, you must not use that value to configure a UDN joinSubnets field. If the default address values are used anywhere in the cluster’s network you must override it by setting the joinSubnets field. For more information, see "Additional configuration details for a UserDefinedNetworks CR".

18.2.1.4. Creating a UserDefinedNetwork custom resource

The following procedure creates a user-defined network that is namespace scoped. Based upon your use case, create your request using either the my-layer-two-udn.yaml example for a Layer2 topology type or the my-layer-three-udn.yaml example for a Layer3 topology type.

Procedure

  1. Create a request for either a Layer2 or Layer3 topology type user-defined network:

    1. Create a YAML file, such as my-layer-two-udn.yaml, to define your request for a Layer2 topology as in the following example: 

      apiVersion: k8s.ovn.org/v1
kind: UserDefinedNetwork
metadata:
  name: udn-1 1
  namespace: <some_custom_namespace>
spec:
  topology: Layer2 2
  layer2: 3
    role: Primary 4
    subnets:
      - "10.0.0.0/24"
      - "2001:db8::/60" 5
      1
      Name of your UserDefinedNetwork resource. This should not be default or duplicate any global namespaces created by the Cluster Network Operator (CNO).
      2
      The topology field describes the network configuration; accepted values are Layer2 and Layer3. Specifying a Layer2 topology type creates one logical switch that is shared by all nodes.
      3
      This field specifies the topology configuration. It can be layer2 or layer3.
      4
      Specifies Primary or Secondary. Primary is the only role specification supported in 4.17.
      5
      For Layer2 topology types the following specifies config details for the subnet field:
      • The subnets field is optional.
      • The subnets field is of type string and accepts standard CIDR formats for both IPv4 and IPv6.
      • The subnets field accepts one or two items. For two items, they must be of a different family. For example, subnets values of 10.100.0.0/16 and 2001:db8::/64.
      • Layer2 subnets can be omitted. If omitted, users must configure IP addresses for the pods. As a consequence, port security only prevents MAC spoofing.
      • The Layer2 subnets field is mandatory when the ipamLifecycle field is specified.

    2. Create a YAML file, such as my-layer-three-udn.yaml, to define your request for a Layer3 topology as in the following example: 

      apiVersion: k8s.ovn.org/v1
kind: UserDefinedNetwork
metadata:
  name: udn-2-primary 1
  namespace: <some_custom_namespace>
spec:
  topology: Layer3 2
  layer3: 3
    role: Primary 4
    subnets: 5
      - cidr: 10.150.0.0/16
        hostSubnet: 24
      - cidr: 2001:db8::/60
        hostSubnet: 64
      1
      Name of your UserDefinedNetwork resource. This should not be default or duplicate any global namespaces created by the Cluster Network Operator (CNO).
      2
      The topology field describes the network configuration; accepted values are Layer2 and Layer3. Specifying a Layer3 topology type creates a layer 2 segment per node, each with a different subnet. Layer 3 routing is used to interconnect node subnets.
      3
      This field specifies the topology configuration. Valid values are layer2 or layer3.
      4
      Specifies a Primary or Secondary role. Primary is the only role specification supported in 4.17 .
      5
      For Layer3 topology types the following specifies config details for the subnet field:
      • The subnets field is mandatory.

      • The type for the subnets field is cidr and hostSubnet:

        • cidr is the cluster subnet and accepts a string value.
        • hostSubnet specifies the nodes subnet prefix that the cluster subnet is split to.
        • For IPv6, only a /64 length is supported for hostSubnet.

  2. Apply your request by running the following command: 

    $ oc apply -f <my_layer_two_udn.yaml>

    Where <my_layer_two_udn.yaml> is the name of your Layer2 or Layer3 configuration file.

  3. Verify that your request is successful by running the following command: 

    $ oc get userdefinednetworks udn-1 -n <some_custom_namespace> -o yaml

    Where some_custom_namespace is the namespace you created for your user-defined network.

    Example output

    apiVersion: k8s.ovn.org/v1
kind: UserDefinedNetwork
metadata:
  creationTimestamp: "2024-08-28T17:18:47Z"
  finalizers:
  - k8s.ovn.org/user-defined-network-protection
  generation: 1
  name: udn-1
  namespace: some-custom-namespace
  resourceVersion: "53313"
  uid: f483626d-6846-48a1-b88e-6bbeb8bcde8c
spec:
  layer2:
    role: Primary
    subnets:
    - 10.0.0.0/24
    - 2001:db8::/60
  topology: Layer2
status:
  conditions:
  - lastTransitionTime: "2024-08-28T17:18:47Z"
    message: NetworkAttachmentDefinition has been created
    reason: NetworkAttachmentDefinitionReady
    status: "True"
    type: NetworkReady

18.2.1.4.1. Additional configuration details for a UserDefinedNetworks CR

The following table explains additional configurations for UDN that are optional. It is not recommended to set these fields without explicit need and understanding of OVN-Kubernetes network topology.

Table 18.1. UserDefinedNetworks optional configurations
FieldTypeDescription

spec.joinSubnets

object

When omitted, the platform sets default values for the joinSubnets field of 100.65.0.0/16 for IPv4 and fd99::/64 for IPv6. If the default address values are used anywhere in the cluster’s network you must override it by setting the joinSubnets field. If you choose to set this field, ensure it does not conflict with other subnets in the cluster such as the cluster subnet, the default network cluster subnet, and the masquerade subnet.

The joinSubnets field configures the routing between different segments within a user-defined network. Dual-stack clusters can set 2 subnets, one for each IP family; otherwise, only 1 subnet is allowed. This field is only allowed for the Primary network.

spec.IPAMLifecycle

object

The IPAMLifecycle field configures the IP address management system (IPAM). You might use this field for virtual workloads to ensure persistent IP addresses. This field is allowed when topology is layer2. The subnets field must be specified when this field is specified. Setting a value of Persistent ensures that your virtual workloads have persistent IP addresses across reboots and migration. These are assigned by the container network interface (CNI) and used by OVN-Kubernetes to program pod IP addresses. You must not change this for pod annotations.

spec.layer2.mtu and spec.layer3.mtu

integer

The maximum transmission units (MTU). The default value is 1400. The boundary for IPv4 is 574, and for IPv6 it is 1280.

18.2.2. Creating primary networks using a NetworkAttachmentDefinition

The following sections explain how to create and manage additional primary networks using the NetworkAttachmentDefinition (NAD) resource.

18.2.2.1. Approaches to managing an additional network

You can manage the life cycle of an additional network created by NAD with one of the following two approaches:

  • By modifying the Cluster Network Operator (CNO) configuration. With this method, the CNO automatically creates and manages the NetworkAttachmentDefinition object. In addition to managing the object lifecycle, the CNO ensures that a DHCP is available for an additional network that uses a DHCP assigned IP address.
  • By applying a YAML manifest. With this method, you can manage the additional network directly by creating an NetworkAttachmentDefinition object. This approach allows for the invocation of multiple CNI plugins in order to attach additional network interfaces in a pod.

Each approach is mutually exclusive and you can only use one approach for managing an additional network at a time. For either approach, the additional network is managed by a Container Network Interface (CNI) plugin that you configure.

Note

When deploying OpenShift Container Platform nodes with multiple network interfaces on Red Hat OpenStack Platform (RHOSP) with OVN SDN, DNS configuration of the secondary interface might take precedence over the DNS configuration of the primary interface. In this case, remove the DNS nameservers for the the subnet ID that is attached to the secondary interface by running the following command: 

$ openstack subnet set --dns-nameserver 0.0.0.0 <subnet_id>

18.2.2.2. Creating an additional network attachment with the Cluster Network Operator

The Cluster Network Operator (CNO) manages additional network definitions. When you specify an additional network to create, the CNO creates the NetworkAttachmentDefinition CRD automatically.

Important

Do not edit the NetworkAttachmentDefinition CRDs that the Cluster Network Operator manages. Doing so might disrupt network traffic on your additional network.

Prerequisites

  • Install the OpenShift CLI (oc).
  • Log in as a user with cluster-admin privileges.

Procedure

  1. Optional: Create the namespace for the additional networks: 

    $ oc create namespace <namespace_name>

  2. To edit the CNO configuration, enter the following command: 

    $ oc edit networks.operator.openshift.io cluster

  3. Modify the CR that you are creating by adding the configuration for the additional network that you are creating, as in the following example CR. 

    apiVersion: operator.openshift.io/v1
kind: Network
metadata:
  name: cluster
spec:
  # ...
  additionalNetworks:
  - name: tertiary-net
    namespace: namespace2
    type: Raw
    rawCNIConfig: |-
      {
        "cniVersion": "0.3.1",
        "name": "tertiary-net",
        "type": "ipvlan",
        "master": "eth1",
        "mode": "l2",
        "ipam": {
          "type": "static",
          "addresses": [
            {
              "address": "192.168.1.23/24"
            }
          ]
        }
      }
  4. Save your changes and quit the text editor to commit your changes.

Verification

  • Confirm that the CNO created the NetworkAttachmentDefinition CRD by running the following command. There might be a delay before the CNO creates the CRD. 

    $ oc get network-attachment-definitions -n <namespace>

    where:

    <namespace>
    Specifies the namespace for the network attachment that you added to the CNO configuration.

    Example output

    NAME                 AGE
test-network-1       14m

18.2.2.2.1. Configuration for an additional network attachment

An additional network is configured by using the NetworkAttachmentDefinition API in the k8s.cni.cncf.io API group.

The configuration for the API is described in the following table:

Table 18.2. NetworkAttachmentDefinition API fields
FieldTypeDescription

metadata.name

string

The name for the additional network.

metadata.namespace

string

The namespace that the object is associated with.

spec.config

string

The CNI plugin configuration in JSON format.

18.2.2.3. Creating an additional network attachment by applying a YAML manifest

Prerequisites

  • Install the OpenShift CLI (oc).
  • Log in as a user with cluster-admin privileges.

Procedure

  1. Create a YAML file with your additional network configuration, such as in the following example: 

    apiVersion: k8s.cni.cncf.io/v1
kind: NetworkAttachmentDefinition
metadata:
  name: next-net
spec:
  config: |-
    {
      "cniVersion": "0.3.1",
      "name": "work-network",
      "type": "host-device",
      "device": "eth1",
      "ipam": {
        "type": "dhcp"
      }
    }

  2. To create the additional network, enter the following command: 

    $ oc apply -f <file>.yaml

    where:

    <file>
    Specifies the name of the file contained the YAML manifest.

18.3. Secondary networks

18.3.1. Creating secondary networks on OVN-Kubernetes

As a cluster administrator, you can configure an additional secondary network for your cluster using the NetworkAttachmentDefinition (NAD) resource.

Note

Support for user-defined networks as a secondary network will be added in a future version of OpenShift Container Platform.

18.3.1.1. Configuration for an OVN-Kubernetes additional network

The Red Hat OpenShift Networking OVN-Kubernetes network plugin allows the configuration of secondary network interfaces for pods. To configure secondary network interfaces, you must define the configurations in the NetworkAttachmentDefinition custom resource definition (CRD).

Note

Pod and multi-network policy creation might remain in a pending state until the OVN-Kubernetes control plane agent in the nodes processes the associated network-attachment-definition CRD.

You can configure an OVN-Kubernetes additional network in either layer 2 or localnet topologies.

  • A layer 2 topology supports east-west cluster traffic, but does not allow access to the underlying physical network.
  • A localnet topology allows connections to the physical network, but requires additional configuration of the underlying Open vSwitch (OVS) bridge on cluster nodes.

The following sections provide example configurations for each of the topologies that OVN-Kubernetes currently allows for secondary networks.

Note

Networks names must be unique. For example, creating multiple NetworkAttachmentDefinition CRDs with different configurations that reference the same network is unsupported.

18.3.1.1.1. Supported platforms for OVN-Kubernetes additional network

You can use an OVN-Kubernetes additional network with the following supported platforms:

  • Bare metal
  • IBM Power®
  • IBM Z®
  • IBM® LinuxONE
  • VMware vSphere
  • Red Hat OpenStack Platform (RHOSP)
18.3.1.1.2. OVN-Kubernetes network plugin JSON configuration table

The following table describes the configuration parameters for the OVN-Kubernetes CNI network plugin:

Table 18.3. OVN-Kubernetes network plugin JSON configuration table
FieldTypeDescription

cniVersion

string

The CNI specification version. The required value is 0.3.1.

name

string

The name of the network. These networks are not namespaced. For example, you can have a network named l2-network referenced from two different NetworkAttachmentDefinition CRDs that exist on two different namespaces. This ensures that pods making use of the NetworkAttachmentDefinition CRD on their own different namespaces can communicate over the same secondary network. However, those two different NetworkAttachmentDefinition CRDs must also share the same network specific parameters such as topology, subnets, mtu, and excludeSubnets.

type

string

The name of the CNI plugin to configure. This value must be set to ovn-k8s-cni-overlay.

topology

string

The topological configuration for the network. Must be one of layer2 or localnet.

subnets

string

The subnet to use for the network across the cluster.

For "topology":"layer2" deployments, IPv6 (2001:DBB::/64) and dual-stack (192.168.100.0/24,2001:DBB::/64) subnets are supported.

When omitted, the logical switch implementing the network only provides layer 2 communication, and users must configure IP addresses for the pods. Port security only prevents MAC spoofing.

mtu

string

The maximum transmission unit (MTU). The default value, 1300, is automatically set by the kernel.

netAttachDefName

string

The metadata namespace and name of the network attachment definition CRD where this configuration is included. For example, if this configuration is defined in a NetworkAttachmentDefinition CRD in namespace ns1 named l2-network, this should be set to ns1/l2-network.

excludeSubnets

string

A comma-separated list of CIDRs and IP addresses. IP addresses are removed from the assignable IP address pool and are never passed to the pods.

vlanID

integer

If topology is set to localnet, the specified VLAN tag is assigned to traffic from this additional network. The default is to not assign a VLAN tag.

18.3.1.1.3. Compatibility with multi-network policy

The multi-network policy API, which is provided by the MultiNetworkPolicy custom resource definition (CRD) in the k8s.cni.cncf.io API group, is compatible with an OVN-Kubernetes secondary network. When defining a network policy, the network policy rules that can be used depend on whether the OVN-Kubernetes secondary network defines the subnets field. Refer to the following table for details:

Table 18.4. Supported multi-network policy selectors based on subnets CNI configuration
subnets field specifiedAllowed multi-network policy selectors

Yes

  • podSelector and namespaceSelector
  • ipBlock

No

  • ipBlock

For example, the following multi-network policy is valid only if the subnets field is defined in the additional network CNI configuration for the additional network named blue2:

Example multi-network policy that uses a pod selector

apiVersion: k8s.cni.cncf.io/v1beta1
kind: MultiNetworkPolicy
metadata:
  name: allow-same-namespace
  annotations:
    k8s.v1.cni.cncf.io/policy-for: blue2
spec:
  podSelector:
  ingress:
  - from:
    - podSelector: {}

The following example uses the ipBlock network policy selector, which is always valid for an OVN-Kubernetes additional network:

Example multi-network policy that uses an IP block selector

apiVersion: k8s.cni.cncf.io/v1beta1
kind: MultiNetworkPolicy
metadata:
  name:  ingress-ipblock
  annotations:
    k8s.v1.cni.cncf.io/policy-for: default/flatl2net
spec:
  podSelector:
    matchLabels:
      name: access-control
  policyTypes:
  - Ingress
  ingress:
  - from:
    - ipBlock:
        cidr: 10.200.0.0/30

18.3.1.1.4. Configuration for a localnet switched topology

The switched localnet topology interconnects the workloads created as Network Attachment Definitions (NADs) through a cluster-wide logical switch to a physical network.

You must map an additional network to the OVN bridge to use it as an OVN-Kubernetes additional network. Bridge mappings allow network traffic to reach the physical network. A bridge mapping associates a physical network name, also known as an interface label, to a bridge created with Open vSwitch (OVS).

You can create an NodeNetworkConfigurationPolicy object, part of the nmstate.io/v1 API group, to declaratively create the mapping. This API is provided by the NMState Operator. By using this API you can apply the bridge mapping to nodes that match your specified nodeSelector expression, such as node-role.kubernetes.io/worker: ''.

When attaching an additional network, you can either use the existing br-ex bridge or create a new bridge. Which approach to use depends on your specific network infrastructure.

  • If your nodes include only a single network interface, you must use the existing bridge. This network interface is owned and managed by OVN-Kubernetes and you must not remove it from the br-ex bridge or alter the interface configuration. If you remove or alter the network interface, your cluster network will stop working correctly.
  • If your nodes include several network interfaces, you can attach a different network interface to a new bridge, and use that for your additional network. This approach provides for traffic isolation from your primary cluster network.

The localnet1 network is mapped to the br-ex bridge in the following example:

Example mapping for sharing a bridge

apiVersion: nmstate.io/v1
kind: NodeNetworkConfigurationPolicy
metadata:
  name: mapping 1
spec:
  nodeSelector:
    node-role.kubernetes.io/worker: '' 2
  desiredState:
    ovn:
      bridge-mappings:
      - localnet: localnet1 3
        bridge: br-ex 4
        state: present 5

1
The name for the configuration object.
2
A node selector that specifies the nodes to apply the node network configuration policy to.
3
The name for the additional network from which traffic is forwarded to the OVS bridge. This additional network must match the name of the spec.config.name field of the NetworkAttachmentDefinition CRD that defines the OVN-Kubernetes additional network.
4
The name of the OVS bridge on the node. This value is required only if you specify state: present.
5
The state for the mapping. Must be either present to add the bridge or absent to remove the bridge. The default value is present.

In the following example, the localnet2 network interface is attached to the ovs-br1 bridge. Through this attachment, the network interface is available to the OVN-Kubernetes network plugin as an additional network.

Example mapping for nodes with multiple interfaces

apiVersion: nmstate.io/v1
kind: NodeNetworkConfigurationPolicy
metadata:
  name: ovs-br1-multiple-networks 1
spec:
  nodeSelector:
    node-role.kubernetes.io/worker: '' 2
  desiredState:
    interfaces:
    - name: ovs-br1 3
      description: |-
        A dedicated OVS bridge with eth1 as a port
        allowing all VLANs and untagged traffic
      type: ovs-bridge
      state: up
      bridge:
        allow-extra-patch-ports: true
        options:
          stp: false
        port:
        - name: eth1 4
    ovn:
      bridge-mappings:
      - localnet: localnet2 5
        bridge: ovs-br1 6
        state: present 7

1
The name for the configuration object.
2
A node selector that specifies the nodes to apply the node network configuration policy to.
3
A new OVS bridge, separate from the default bridge used by OVN-Kubernetes for all cluster traffic.
4
A network device on the host system to associate with this new OVS bridge.
5
The name for the additional network from which traffic is forwarded to the OVS bridge. This additional network must match the name of the spec.config.name field of the NetworkAttachmentDefinition CRD that defines the OVN-Kubernetes additional network.
6
The name of the OVS bridge on the node. This value is required only if you specify state: present.
7
The state for the mapping. Must be either present to add the bridge or absent to remove the bridge. The default value is present.

This declarative approach is recommended because the NMState Operator applies additional network configuration to all nodes specified by the node selector automatically and transparently.

The following JSON example configures a localnet secondary network: 

{
  "cniVersion": "0.3.1",
  "name": "ns1-localnet-network",
  "type": "ovn-k8s-cni-overlay",
  "topology":"localnet",
  "subnets": "202.10.130.112/28",
  "vlanID": 33,
  "mtu": 1500,
  "netAttachDefName": "ns1/localnet-network"
  "excludeSubnets": "10.100.200.0/29"
}
18.3.1.1.4.1. Configuration for a layer 2 switched topology

The switched (layer 2) topology networks interconnect the workloads through a cluster-wide logical switch. This configuration can be used for IPv6 and dual-stack deployments.

Note

Layer 2 switched topology networks only allow for the transfer of data packets between pods within a cluster.

The following JSON example configures a switched secondary network: 

{
  "cniVersion": "0.3.1",
  "name": "l2-network",
  "type": "ovn-k8s-cni-overlay",
  "topology":"layer2",
  "subnets": "10.100.200.0/24",
  "mtu": 1300,
  "netAttachDefName": "ns1/l2-network",
  "excludeSubnets": "10.100.200.0/29"
}
18.3.1.1.5. Configuring pods for additional networks

You must specify the secondary network attachments through the k8s.v1.cni.cncf.io/networks annotation.

The following example provisions a pod with two secondary attachments, one for each of the attachment configurations presented in this guide. 

apiVersion: v1
kind: Pod
metadata:
  annotations:
    k8s.v1.cni.cncf.io/networks: l2-network
  name: tinypod
  namespace: ns1
spec:
  containers:
  - args:
    - pause
    image: k8s.gcr.io/e2e-test-images/agnhost:2.36
    imagePullPolicy: IfNotPresent
    name: agnhost-container
18.3.1.1.6. Configuring pods with a static IP address

The following example provisions a pod with a static IP address.

Note
  • You can only specify the IP address for a pod’s secondary network attachment for layer 2 attachments.
  • Specifying a static IP address for the pod is only possible when the attachment configuration does not feature subnets. 
apiVersion: v1
kind: Pod
metadata:
  annotations:
    k8s.v1.cni.cncf.io/networks: '[
      {
        "name": "l2-network", 1
        "mac": "02:03:04:05:06:07", 2
        "interface": "myiface1", 3
        "ips": [
          "192.0.2.20/24"
          ] 4
      }
    ]'
  name: tinypod
  namespace: ns1
spec:
  containers:
  - args:
    - pause
    image: k8s.gcr.io/e2e-test-images/agnhost:2.36
    imagePullPolicy: IfNotPresent
    name: agnhost-container
1
The name of the network. This value must be unique across all NetworkAttachmentDefinition CRDs.
2
The MAC address to be assigned for the interface.
3
The name of the network interface to be created for the pod.
4
The IP addresses to be assigned to the network interface.

18.3.2. Creating secondary networks with other CNI plugins

The specific configuration fields for additional networks are described in the following sections.

18.3.2.1. Configuration for a bridge additional network

The following object describes the configuration parameters for the Bridge CNI plugin:

Table 18.5. Bridge CNI plugin JSON configuration object
FieldTypeDescription

cniVersion

string

The CNI specification version. The 0.3.1 value is required.

name

string

The value for the name parameter you provided previously for the CNO configuration.

type

string

The name of the CNI plugin to configure: bridge.

ipam

object

The configuration object for the IPAM CNI plugin. The plugin manages IP address assignment for the attachment definition.

bridge

string

Optional: Specify the name of the virtual bridge to use. If the bridge interface does not exist on the host, it is created. The default value is cni0.

ipMasq

boolean

Optional: Set to true to enable IP masquerading for traffic that leaves the virtual network. The source IP address for all traffic is rewritten to the bridge’s IP address. If the bridge does not have an IP address, this setting has no effect. The default value is false.

isGateway

boolean

Optional: Set to true to assign an IP address to the bridge. The default value is false.

isDefaultGateway

boolean

Optional: Set to true to configure the bridge as the default gateway for the virtual network. The default value is false. If isDefaultGateway is set to true, then isGateway is also set to true automatically.

forceAddress

boolean

Optional: Set to true to allow assignment of a previously assigned IP address to the virtual bridge. When set to false, if an IPv4 address or an IPv6 address from overlapping subsets is assigned to the virtual bridge, an error occurs. The default value is false.

hairpinMode

boolean

Optional: Set to true to allow the virtual bridge to send an Ethernet frame back through the virtual port it was received on. This mode is also known as reflective relay. The default value is false.

promiscMode

boolean

Optional: Set to true to enable promiscuous mode on the bridge. The default value is false.

vlan

string

Optional: Specify a virtual LAN (VLAN) tag as an integer value. By default, no VLAN tag is assigned.

preserveDefaultVlan

string

Optional: Indicates whether the default vlan must be preserved on the veth end connected to the bridge. Defaults to true.

vlanTrunk

list

Optional: Assign a VLAN trunk tag. The default value is none.

mtu

integer

Optional: Set the maximum transmission unit (MTU) to the specified value. The default value is automatically set by the kernel.

enabledad

boolean

Optional: Enables duplicate address detection for the container side veth. The default value is false.

macspoofchk

boolean

Optional: Enables mac spoof check, limiting the traffic originating from the container to the mac address of the interface. The default value is false.

Note

The VLAN parameter configures the VLAN tag on the host end of the veth and also enables the vlan_filtering feature on the bridge interface.

Note

To configure an uplink for an L2 network, you must allow the VLAN on the uplink interface by using the following command: 

$  bridge vlan add vid VLAN_ID dev DEV
18.3.2.1.1. Bridge CNI plugin configuration example

The following example configures an additional network named bridge-net: 

{
  "cniVersion": "0.3.1",
  "name": "bridge-net",
  "type": "bridge",
  "isGateway": true,
  "vlan": 2,
  "ipam": {
    "type": "dhcp"
    }
}

18.3.2.2. Configuration for a host device additional network

Note

Specify your network device by setting only one of the following parameters: device,hwaddr, kernelpath, or pciBusID.

The following object describes the configuration parameters for the host-device CNI plugin:

Table 18.6. Host device CNI plugin JSON configuration object
FieldTypeDescription

cniVersion

string

The CNI specification version. The 0.3.1 value is required.

name

string

The value for the name parameter you provided previously for the CNO configuration.

type

string

The name of the CNI plugin to configure: host-device.

device

string

Optional: The name of the device, such as eth0.

hwaddr

string

Optional: The device hardware MAC address.

kernelpath

string

Optional: The Linux kernel device path, such as /sys/devices/pci0000:00/0000:00:1f.6.

pciBusID

string

Optional: The PCI address of the network device, such as 0000:00:1f.6.

18.3.2.2.1. host-device configuration example

The following example configures an additional network named hostdev-net: 

{
  "cniVersion": "0.3.1",
  "name": "hostdev-net",
  "type": "host-device",
  "device": "eth1"
}

18.3.2.3. Configuration for a VLAN additional network

The following object describes the configuration parameters for the VLAN, vlan, CNI plugin:

Table 18.7. VLAN CNI plugin JSON configuration object
FieldTypeDescription

cniVersion

string

The CNI specification version. The 0.3.1 value is required.

name

string

The value for the name parameter you provided previously for the CNO configuration.

type

string

The name of the CNI plugin to configure: vlan.

master

string

The Ethernet interface to associate with the network attachment. If a master is not specified, the interface for the default network route is used.

vlanId

integer

Set the ID of the vlan.

ipam

object

The configuration object for the IPAM CNI plugin. The plugin manages IP address assignment for the attachment definition.

mtu

integer

Optional: Set the maximum transmission unit (MTU) to the specified value. The default value is automatically set by the kernel.

dns

integer

Optional: DNS information to return. For example, a priority-ordered list of DNS nameservers.

linkInContainer

boolean

Optional: Specifies whether the master interface is in the container network namespace or the main network namespace. Set the value to true to request the use of a container namespace master interface.

Important

A NetworkAttachmentDefinition custom resource definition (CRD) with a vlan configuration can be used only on a single pod in a node because the CNI plugin cannot create multiple vlan subinterfaces with the same vlanId on the same master interface.

18.3.2.3.1. VLAN configuration example

The following example demonstrates a vlan configuration with an additional network that is named vlan-net: 

{
  "name": "vlan-net",
  "cniVersion": "0.3.1",
  "type": "vlan",
  "master": "eth0",
  "mtu": 1500,
  "vlanId": 5,
  "linkInContainer": false,
  "ipam": {
      "type": "host-local",
      "subnet": "10.1.1.0/24"
  },
  "dns": {
      "nameservers": [ "10.1.1.1", "8.8.8.8" ]
  }
}

18.3.2.4. Configuration for an IPVLAN additional network

The following object describes the configuration parameters for the IPVLAN, ipvlan, CNI plugin:

Table 18.8. IPVLAN CNI plugin JSON configuration object
FieldTypeDescription

cniVersion

string

The CNI specification version. The 0.3.1 value is required.

name

string

The value for the name parameter you provided previously for the CNO configuration.

type

string

The name of the CNI plugin to configure: ipvlan.

ipam

object

The configuration object for the IPAM CNI plugin. The plugin manages IP address assignment for the attachment definition. This is required unless the plugin is chained.

mode

string

Optional: The operating mode for the virtual network. The value must be l2, l3, or l3s. The default value is l2.

master

string

Optional: The Ethernet interface to associate with the network attachment. If a master is not specified, the interface for the default network route is used.

mtu

integer

Optional: Set the maximum transmission unit (MTU) to the specified value. The default value is automatically set by the kernel.

linkInContainer

boolean

Optional: Specifies whether the master interface is in the container network namespace or the main network namespace. Set the value to true to request the use of a container namespace master interface.

Important
  • The ipvlan object does not allow virtual interfaces to communicate with the master interface. Therefore the container is not able to reach the host by using the ipvlan interface. Be sure that the container joins a network that provides connectivity to the host, such as a network supporting the Precision Time Protocol (PTP).
  • A single master interface cannot simultaneously be configured to use both macvlan and ipvlan.
  • For IP allocation schemes that cannot be interface agnostic, the ipvlan plugin can be chained with an earlier plugin that handles this logic. If the master is omitted, then the previous result must contain a single interface name for the ipvlan plugin to enslave. If ipam is omitted, then the previous result is used to configure the ipvlan interface.
18.3.2.4.1. IPVLAN CNI plugin configuration example

The following example configures an additional network named ipvlan-net: 

{
  "cniVersion": "0.3.1",
  "name": "ipvlan-net",
  "type": "ipvlan",
  "master": "eth1",
  "linkInContainer": false,
  "mode": "l3",
  "ipam": {
    "type": "static",
    "addresses": [
       {
         "address": "192.168.10.10/24"
       }
    ]
  }
}

18.3.2.5. Configuration for a macvlan additional network

The following object describes the configuration parameters for the MACVLAN CNI plugin:

Table 18.9. MACVLAN CNI plugin JSON configuration object
FieldTypeDescription

cniVersion

string

The CNI specification version. The 0.3.1 value is required.

name

string

The value for the name parameter you provided previously for the CNO configuration.

type

string

The name of the CNI plugin to configure: macvlan.

ipam

object

The configuration object for the IPAM CNI plugin. The plugin manages IP address assignment for the attachment definition.

mode

string

Optional: Configures traffic visibility on the virtual network. Must be either bridge, passthru, private, or vepa. If a value is not provided, the default value is bridge.

master

string

Optional: The host network interface to associate with the newly created macvlan interface. If a value is not specified, then the default route interface is used.

mtu

string

Optional: The maximum transmission unit (MTU) to the specified value. The default value is automatically set by the kernel.

linkInContainer

boolean

Optional: Specifies whether the master interface is in the container network namespace or the main network namespace. Set the value to true to request the use of a container namespace master interface.

Note

If you specify the master key for the plugin configuration, use a different physical network interface than the one that is associated with your primary network plugin to avoid possible conflicts.

18.3.2.5.1. MACVLAN CNI plugin configuration example

The following example configures an additional network named macvlan-net: 

{
  "cniVersion": "0.3.1",
  "name": "macvlan-net",
  "type": "macvlan",
  "master": "eth1",
  "linkInContainer": false,
  "mode": "bridge",
  "ipam": {
    "type": "dhcp"
    }
}

18.3.2.6. Configuration for a TAP additional network

The following object describes the configuration parameters for the TAP CNI plugin:

Table 18.10. TAP CNI plugin JSON configuration object
FieldTypeDescription

cniVersion

string

The CNI specification version. The 0.3.1 value is required.

name

string

The value for the name parameter you provided previously for the CNO configuration.

type

string

The name of the CNI plugin to configure: tap.

mac

string

Optional: Request the specified MAC address for the interface.

mtu

integer

Optional: Set the maximum transmission unit (MTU) to the specified value. The default value is automatically set by the kernel.

selinuxcontext

string

Optional: The SELinux context to associate with the tap device.

Note

The value system_u:system_r:container_t:s0 is required for OpenShift Container Platform.

multiQueue

boolean

Optional: Set to true to enable multi-queue.

owner

integer

Optional: The user owning the tap device.

group

integer

Optional: The group owning the tap device.

bridge

string

Optional: Set the tap device as a port of an already existing bridge.

18.3.2.6.1. Tap configuration example

The following example configures an additional network named mynet: 

{
 "name": "mynet",
 "cniVersion": "0.3.1",
 "type": "tap",
 "mac": "00:11:22:33:44:55",
 "mtu": 1500,
 "selinuxcontext": "system_u:system_r:container_t:s0",
 "multiQueue": true,
 "owner": 0,
 "group": 0
 "bridge": "br1"
}
18.3.2.6.2. Setting SELinux boolean for the TAP CNI plugin

To create the tap device with the container_t SELinux context, enable the container_use_devices boolean on the host by using the Machine Config Operator (MCO).

Prerequisites

  • You have installed the OpenShift CLI (oc).

Procedure

  1. Create a new YAML file named, such as setsebool-container-use-devices.yaml, with the following details: 

    apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfig
metadata:
  labels:
    machineconfiguration.openshift.io/role: worker
  name: 99-worker-setsebool
spec:
  config:
    ignition:
      version: 3.2.0
    systemd:
      units:
      - enabled: true
        name: setsebool.service
        contents: |
          [Unit]
          Description=Set SELinux boolean for the TAP CNI plugin
          Before=kubelet.service

          [Service]
          Type=oneshot
          ExecStart=/usr/sbin/setsebool container_use_devices=on
          RemainAfterExit=true

          [Install]
          WantedBy=multi-user.target graphical.target

  2. Create the new MachineConfig object by running the following command: 

    $ oc apply -f setsebool-container-use-devices.yaml
    Note

    Applying any changes to the MachineConfig object causes all affected nodes to gracefully reboot after the change is applied. This update can take some time to be applied.

  3. Verify the change is applied by running the following command: 

    $ oc get machineconfigpools

    Expected output

    NAME        CONFIG                                                UPDATED   UPDATING   DEGRADED   MACHINECOUNT   READYMACHINECOUNT   UPDATEDMACHINECOUNT   DEGRADEDMACHINECOUNT   AGE
master      rendered-master-e5e0c8e8be9194e7c5a882e047379cfa      True      False      False      3              3                   3                     0                      7d2h
worker      rendered-worker-d6c9ca107fba6cd76cdcbfcedcafa0f2      True      False      False      3              3                   3                     0                      7d

    Note

    All nodes should be in the updated and ready state.

Additional resources

18.3.3. Attaching a pod to an additional network

As a cluster user you can attach a pod to an additional network.

18.3.3.1. Adding a pod to an additional network

You can add a pod to an additional network. The pod continues to send normal cluster-related network traffic over the default network.

When a pod is created additional networks are attached to it. However, if a pod already exists, you cannot attach additional networks to it.

The pod must be in the same namespace as the additional network.

Prerequisites

  • Install the OpenShift CLI (oc).
  • Log in to the cluster.

Procedure

  1. Add an annotation to the Pod object. Only one of the following annotation formats can be used:

    1. To attach an additional network without any customization, add an annotation with the following format. Replace <network> with the name of the additional network to associate with the pod: 

      metadata:
  annotations:
    k8s.v1.cni.cncf.io/networks: <network>[,<network>,...] 1
      1
      To specify more than one additional network, separate each network with a comma. Do not include whitespace between the comma. If you specify the same additional network multiple times, that pod will have multiple network interfaces attached to that network.

    2. To attach an additional network with customizations, add an annotation with the following format: 

      metadata:
  annotations:
    k8s.v1.cni.cncf.io/networks: |-
      [
        {
          "name": "<network>", 1
          "namespace": "<namespace>", 2
          "default-route": ["<default-route>"] 3
        }
      ]
      1
      Specify the name of the additional network defined by a NetworkAttachmentDefinition object.
      2
      Specify the namespace where the NetworkAttachmentDefinition object is defined.
      3
      Optional: Specify an override for the default route, such as 192.168.17.1.

  2. To create the pod, enter the following command. Replace <name> with the name of the pod. 

    $ oc create -f <name>.yaml

  3. Optional: To Confirm that the annotation exists in the Pod CR, enter the following command, replacing <name> with the name of the pod. 

    $ oc get pod <name> -o yaml

    In the following example, the example-pod pod is attached to the net1 additional network: 

    $ oc get pod example-pod -o yaml
apiVersion: v1
kind: Pod
metadata:
  annotations:
    k8s.v1.cni.cncf.io/networks: macvlan-bridge
    k8s.v1.cni.cncf.io/network-status: |- 1
      [{
          "name": "ovn-kubernetes",
          "interface": "eth0",
          "ips": [
              "10.128.2.14"
          ],
          "default": true,
          "dns": {}
      },{
          "name": "macvlan-bridge",
          "interface": "net1",
          "ips": [
              "20.2.2.100"
          ],
          "mac": "22:2f:60:a5:f8:00",
          "dns": {}
      }]
  name: example-pod
  namespace: default
spec:
  ...
status:
  ...
    1
    The k8s.v1.cni.cncf.io/network-status parameter is a JSON array of objects. Each object describes the status of an additional network attached to the pod. The annotation value is stored as a plain text value.
18.3.3.1.1. Specifying pod-specific addressing and routing options

When attaching a pod to an additional network, you may want to specify further properties about that network in a particular pod. This allows you to change some aspects of routing, as well as specify static IP addresses and MAC addresses. To accomplish this, you can use the JSON formatted annotations.

Prerequisites

  • The pod must be in the same namespace as the additional network.
  • Install the OpenShift CLI (oc).
  • You must log in to the cluster.

Procedure

To add a pod to an additional network while specifying addressing and/or routing options, complete the following steps:

  1. Edit the Pod resource definition. If you are editing an existing Pod resource, run the following command to edit its definition in the default editor. Replace <name> with the name of the Pod resource to edit. 

    $ oc edit pod <name>

  2. In the Pod resource definition, add the k8s.v1.cni.cncf.io/networks parameter to the pod metadata mapping. The k8s.v1.cni.cncf.io/networks accepts a JSON string of a list of objects that reference the name of NetworkAttachmentDefinition custom resource (CR) names in addition to specifying additional properties. 

    metadata:
  annotations:
    k8s.v1.cni.cncf.io/networks: '[<network>[,<network>,...]]' 1
    1
    Replace <network> with a JSON object as shown in the following examples. The single quotes are required.

  3. In the following example the annotation specifies which network attachment will have the default route, using the default-route parameter. 

    apiVersion: v1
kind: Pod
metadata:
  name: example-pod
  annotations:
    k8s.v1.cni.cncf.io/networks: '[
    {
      "name": "net1"
    },
    {
      "name": "net2", 1
      "default-route": ["192.0.2.1"] 2
    }]'
spec:
  containers:
  - name: example-pod
    command: ["/bin/bash", "-c", "sleep 2000000000000"]
    image: centos/tools
    1
    The name key is the name of the additional network to associate with the pod.
    2
    The default-route key specifies a value of a gateway for traffic to be routed over if no other routing entry is present in the routing table. If more than one default-route key is specified, this will cause the pod to fail to become active.

The default route will cause any traffic that is not specified in other routes to be routed to the gateway.

Important

Setting the default route to an interface other than the default network interface for OpenShift Container Platform may cause traffic that is anticipated for pod-to-pod traffic to be routed over another interface.

To verify the routing properties of a pod, the oc command may be used to execute the ip command within a pod. 

$ oc exec -it <pod_name> -- ip route
Note

You may also reference the pod’s k8s.v1.cni.cncf.io/network-status to see which additional network has been assigned the default route, by the presence of the default-route key in the JSON-formatted list of objects.

To set a static IP address or MAC address for a pod you can use the JSON formatted annotations. This requires you create networks that specifically allow for this functionality. This can be specified in a rawCNIConfig for the CNO.

  1. Edit the CNO CR by running the following command: 

    $ oc edit networks.operator.openshift.io cluster

The following YAML describes the configuration parameters for the CNO:

Cluster Network Operator YAML configuration

name: <name> 1
namespace: <namespace> 2
rawCNIConfig: '{ 3
  ...
}'
type: Raw

1
Specify a name for the additional network attachment that you are creating. The name must be unique within the specified namespace.
2
Specify the namespace to create the network attachment in. If you do not specify a value, then the default namespace is used.
3
Specify the CNI plugin configuration in JSON format, which is based on the following template.

The following object describes the configuration parameters for utilizing static MAC address and IP address using the macvlan CNI plugin:

macvlan CNI plugin JSON configuration object using static IP and MAC address

{
  "cniVersion": "0.3.1",
  "name": "<name>", 1
  "plugins": [{ 2
      "type": "macvlan",
      "capabilities": { "ips": true }, 3
      "master": "eth0", 4
      "mode": "bridge",
      "ipam": {
        "type": "static"
      }
    }, {
      "capabilities": { "mac": true }, 5
      "type": "tuning"
    }]
}

1
Specifies the name for the additional network attachment to create. The name must be unique within the specified namespace.
2
Specifies an array of CNI plugin configurations. The first object specifies a macvlan plugin configuration and the second object specifies a tuning plugin configuration.
3
Specifies that a request is made to enable the static IP address functionality of the CNI plugin runtime configuration capabilities.
4
Specifies the interface that the macvlan plugin uses.
5
Specifies that a request is made to enable the static MAC address functionality of a CNI plugin.

The above network attachment can be referenced in a JSON formatted annotation, along with keys to specify which static IP and MAC address will be assigned to a given pod.

Edit the pod with: 

$ oc edit pod <name>

macvlan CNI plugin JSON configuration object using static IP and MAC address

apiVersion: v1
kind: Pod
metadata:
  name: example-pod
  annotations:
    k8s.v1.cni.cncf.io/networks: '[
      {
        "name": "<name>", 1
        "ips": [ "192.0.2.205/24" ], 2
        "mac": "CA:FE:C0:FF:EE:00" 3
      }
    ]'

1
Use the <name> as provided when creating the rawCNIConfig above.
2
Provide an IP address including the subnet mask.
3
Provide the MAC address.
Note

Static IP addresses and MAC addresses do not have to be used at the same time, you may use them individually, or together.

To verify the IP address and MAC properties of a pod with additional networks, use the oc command to execute the ip command within a pod. 

$ oc exec -it <pod_name> -- ip a

18.3.4. Configuring multi-network policy

Administrators can use the MultiNetworkPolicy API to create multiple network policies that manage traffic for pods attached to secondary networks. For example, you can create policies that allow or deny traffic based on specific ports, IPs/ranges, or labels.

Multi-network policies can be used to manage traffic on secondary networks in the cluster. They cannot managed the cluster’s default network or primary network of user-defined networks.

As a cluster administrator, you can configure a multi-network policy for any of the following network types:

  • Single-Root I/O Virtualization (SR-IOV)
  • MAC Virtual Local Area Network (MacVLAN)
  • IP Virtual Local Area Network (IPVLAN)
  • Bond Container Network Interface (CNI) over SR-IOV
  • OVN-Kubernetes additional networks
Note

Support for configuring multi-network policies for SR-IOV additional networks is only supported with kernel network interface controllers (NICs). SR-IOV is not supported for Data Plane Development Kit (DPDK) applications.

18.3.4.1. Differences between multi-network policy and network policy

Although the MultiNetworkPolicy API implements the NetworkPolicy API, there are several important differences:

  • You must use the MultiNetworkPolicy API: 

    apiVersion: k8s.cni.cncf.io/v1beta1
kind: MultiNetworkPolicy
  • You must use the multi-networkpolicy resource name when using the CLI to interact with multi-network policies. For example, you can view a multi-network policy object with the oc get multi-networkpolicy <name> command where <name> is the name of a multi-network policy.

  • You must specify an annotation with the name of the network attachment definition that defines the macvlan or SR-IOV additional network: 

    apiVersion: k8s.cni.cncf.io/v1beta1
kind: MultiNetworkPolicy
metadata:
  annotations:
    k8s.v1.cni.cncf.io/policy-for: <network_name>

    where:

    <network_name>
    Specifies the name of a network attachment definition.

18.3.4.2. Enabling multi-network policy for the cluster

As a cluster administrator, you can enable multi-network policy support on your cluster.

Prerequisites

  • Install the OpenShift CLI (oc).
  • Log in to the cluster with a user with cluster-admin privileges.

Procedure

  1. Create the multinetwork-enable-patch.yaml file with the following YAML: 

    apiVersion: operator.openshift.io/v1
kind: Network
metadata:
  name: cluster
spec:
  useMultiNetworkPolicy: true

  2. Configure the cluster to enable multi-network policy: 

    $ oc patch network.operator.openshift.io cluster --type=merge --patch-file=multinetwork-enable-patch.yaml

    Example output

    network.operator.openshift.io/cluster patched

18.3.4.3. Supporting multi-network policies in IPv6 networks

The ICMPv6 Neighbor Discovery Protocol (NDP) is a set of messages and processes that enable devices to discover and maintain information about neighboring nodes. NDP plays a crucial role in IPv6 networks, facilitating the interaction between devices on the same link.

The Cluster Network Operator (CNO) deploys the iptables implementation of multi-network policy when the useMultiNetworkPolicy parameter is set to true.

To support multi-network policies in IPv6 networks the Cluster Network Operator deploys the following set of rules in every pod affected by a multi-network policy:

Multi-network policy custom rules

kind: ConfigMap
apiVersion: v1
metadata:
  name: multi-networkpolicy-custom-rules
  namespace: openshift-multus
data:

  custom-v6-rules.txt: |
    # accept NDP
    -p icmpv6 --icmpv6-type neighbor-solicitation -j ACCEPT 1
    -p icmpv6 --icmpv6-type neighbor-advertisement -j ACCEPT 2
    # accept RA/RS
    -p icmpv6 --icmpv6-type router-solicitation -j ACCEPT 3
    -p icmpv6 --icmpv6-type router-advertisement -j ACCEPT 4

1
This rule allows incoming ICMPv6 neighbor solicitation messages, which are part of the neighbor discovery protocol (NDP). These messages help determine the link-layer addresses of neighboring nodes.
2
This rule allows incoming ICMPv6 neighbor advertisement messages, which are part of NDP and provide information about the link-layer address of the sender.
3
This rule permits incoming ICMPv6 router solicitation messages. Hosts use these messages to request router configuration information.
4
This rule allows incoming ICMPv6 router advertisement messages, which give configuration information to hosts.
Note

You cannot edit these predefined rules.

These rules collectively enable essential ICMPv6 traffic for correct network functioning, including address resolution and router communication in an IPv6 environment. With these rules in place and a multi-network policy denying traffic, applications are not expected to experience connectivity issues.

18.3.4.4. Working with multi-network policy

As a cluster administrator, you can create, edit, view, and delete multi-network policies.

18.3.4.4.1. Prerequisites
  • You have enabled multi-network policy support for your cluster.
18.3.4.4.2. Creating a multi-network policy using the CLI

To define granular rules describing ingress or egress network traffic allowed for namespaces in your cluster, you can create a multi-network policy.

Prerequisites

  • Your cluster uses a network plugin that supports NetworkPolicy objects, such as the OVN-Kubernetes network plugin, with mode: NetworkPolicy set.
  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with cluster-admin privileges.
  • You are working in the namespace that the multi-network policy applies to.

Procedure

  1. Create a policy rule:

    1. Create a <policy_name>.yaml file: 

      $ touch <policy_name>.yaml

      where:

      <policy_name>
      Specifies the multi-network policy file name.

    2. Define a multi-network policy in the file that you just created, such as in the following examples:

      Deny ingress from all pods in all namespaces

      This is a fundamental policy, blocking all cross-pod networking other than cross-pod traffic allowed by the configuration of other Network Policies. 

      apiVersion: k8s.cni.cncf.io/v1beta1
kind: MultiNetworkPolicy
metadata:
  name: deny-by-default
  annotations:
    k8s.v1.cni.cncf.io/policy-for:<namespace_name>/<network_name>
spec:
  podSelector: {}
  policyTypes:
  - Ingress
  ingress: []

      where:

      <network_name>
      Specifies the name of a network attachment definition.

      Allow ingress from all pods in the same namespace

      apiVersion: k8s.cni.cncf.io/v1beta1
kind: MultiNetworkPolicy
metadata:
  name: allow-same-namespace
  annotations:
    k8s.v1.cni.cncf.io/policy-for: <network_name>
spec:
  podSelector:
  ingress:
  - from:
    - podSelector: {}

      where:

      <network_name>
      Specifies the name of a network attachment definition.

      Allow ingress traffic to one pod from a particular namespace

      This policy allows traffic to pods labelled pod-a from pods running in namespace-y. 

      apiVersion: k8s.cni.cncf.io/v1beta1
kind: MultiNetworkPolicy
metadata:
  name: allow-traffic-pod
  annotations:
    k8s.v1.cni.cncf.io/policy-for: <network_name>
spec:
  podSelector:
   matchLabels:
      pod: pod-a
  policyTypes:
  - Ingress
  ingress:
  - from:
    - namespaceSelector:
        matchLabels:
           kubernetes.io/metadata.name: namespace-y

      where:

      <network_name>
      Specifies the name of a network attachment definition.

      Restrict traffic to a service

      This policy when applied ensures every pod with both labels app=bookstore and role=api can only be accessed by pods with label app=bookstore. In this example the application could be a REST API server, marked with labels app=bookstore and role=api.

      This example addresses the following use cases:

      • Restricting the traffic to a service to only the other microservices that need to use it.

      • Restricting the connections to a database to only permit the application using it. 

        apiVersion: k8s.cni.cncf.io/v1beta1
kind: MultiNetworkPolicy
metadata:
  name: api-allow
  annotations:
    k8s.v1.cni.cncf.io/policy-for: <network_name>
spec:
  podSelector:
    matchLabels:
      app: bookstore
      role: api
  ingress:
  - from:
      - podSelector:
          matchLabels:
            app: bookstore

        where:

        <network_name>
        Specifies the name of a network attachment definition.

  2. To create the multi-network policy object, enter the following command: 

    $ oc apply -f <policy_name>.yaml -n <namespace>

    where:

    <policy_name>
    Specifies the multi-network policy file name.
    <namespace>
    Optional: Specifies the namespace if the object is defined in a different namespace than the current namespace.

    Example output

    multinetworkpolicy.k8s.cni.cncf.io/deny-by-default created

Note

If you log in to the web console with cluster-admin privileges, you have a choice of creating a network policy in any namespace in the cluster directly in YAML or from a form in the web console.

18.3.4.4.3. Editing a multi-network policy

You can edit a multi-network policy in a namespace.

Prerequisites

  • Your cluster uses a network plugin that supports NetworkPolicy objects, such as the OVN-Kubernetes network plugin, with mode: NetworkPolicy set.
  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with cluster-admin privileges.
  • You are working in the namespace where the multi-network policy exists.

Procedure

  1. Optional: To list the multi-network policy objects in a namespace, enter the following command: 

    $ oc get multi-networkpolicy

    where:

    <namespace>
    Optional: Specifies the namespace if the object is defined in a different namespace than the current namespace.

  2. Edit the multi-network policy object.

    • If you saved the multi-network policy definition in a file, edit the file and make any necessary changes, and then enter the following command. 

      $ oc apply -n <namespace> -f <policy_file>.yaml

      where:

      <namespace>
      Optional: Specifies the namespace if the object is defined in a different namespace than the current namespace.
      <policy_file>
      Specifies the name of the file containing the network policy.

    • If you need to update the multi-network policy object directly, enter the following command: 

      $ oc edit multi-networkpolicy <policy_name> -n <namespace>

      where:

      <policy_name>
      Specifies the name of the network policy.
      <namespace>
      Optional: Specifies the namespace if the object is defined in a different namespace than the current namespace.

  3. Confirm that the multi-network policy object is updated. 

    $ oc describe multi-networkpolicy <policy_name> -n <namespace>

    where:

    <policy_name>
    Specifies the name of the multi-network policy.
    <namespace>
    Optional: Specifies the namespace if the object is defined in a different namespace than the current namespace.
Note

If you log in to the web console with cluster-admin privileges, you have a choice of editing a network policy in any namespace in the cluster directly in YAML or from the policy in the web console through the Actions menu.

18.3.4.4.4. Viewing multi-network policies using the CLI

You can examine the multi-network policies in a namespace.

Prerequisites

  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with cluster-admin privileges.
  • You are working in the namespace where the multi-network policy exists.

Procedure

  • List multi-network policies in a namespace:

    • To view multi-network policy objects defined in a namespace, enter the following command: 

      $ oc get multi-networkpolicy

    • Optional: To examine a specific multi-network policy, enter the following command: 

      $ oc describe multi-networkpolicy <policy_name> -n <namespace>

      where:

      <policy_name>
      Specifies the name of the multi-network policy to inspect.
      <namespace>
      Optional: Specifies the namespace if the object is defined in a different namespace than the current namespace.
Note

If you log in to the web console with cluster-admin privileges, you have a choice of viewing a network policy in any namespace in the cluster directly in YAML or from a form in the web console.

18.3.4.4.5. Deleting a multi-network policy using the CLI

You can delete a multi-network policy in a namespace.

Prerequisites

  • Your cluster uses a network plugin that supports NetworkPolicy objects, such as the OVN-Kubernetes network plugin, with mode: NetworkPolicy set.
  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with cluster-admin privileges.
  • You are working in the namespace where the multi-network policy exists.

Procedure

  • To delete a multi-network policy object, enter the following command: 

    $ oc delete multi-networkpolicy <policy_name> -n <namespace>

    where:

    <policy_name>
    Specifies the name of the multi-network policy.
    <namespace>
    Optional: Specifies the namespace if the object is defined in a different namespace than the current namespace.

    Example output

    multinetworkpolicy.k8s.cni.cncf.io/default-deny deleted

Note

If you log in to the web console with cluster-admin privileges, you have a choice of deleting a network policy in any namespace in the cluster directly in YAML or from the policy in the web console through the Actions menu.

18.3.4.4.6. Creating a default deny all multi-network policy

This is a fundamental policy, blocking all cross-pod networking other than network traffic allowed by the configuration of other deployed network policies. This procedure enforces a default deny-by-default policy.

Note

If you log in with a user with the cluster-admin role, then you can create a network policy in any namespace in the cluster.

Prerequisites

  • Your cluster uses a network plugin that supports NetworkPolicy objects, such as the OVN-Kubernetes network plugin, with mode: NetworkPolicy set.
  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with cluster-admin privileges.
  • You are working in the namespace that the multi-network policy applies to.

Procedure

  1. Create the following YAML that defines a deny-by-default policy to deny ingress from all pods in all namespaces. Save the YAML in the deny-by-default.yaml file: 

    apiVersion: k8s.cni.cncf.io/v1beta1
kind: MultiNetworkPolicy
metadata:
  name: deny-by-default
  namespace: default 1
  annotations:
    k8s.v1.cni.cncf.io/policy-for: <namespace_name>/<network_name> 2
spec:
  podSelector: {} 3
  policyTypes: 4
  - Ingress 5
  ingress: [] 6
    1
    namespace: default deploys this policy to the default namespace.
    2
    network_name: specifies the name of a network attachment definition.
    3
    podSelector: is empty, this means it matches all the pods. Therefore, the policy applies to all pods in the default namespace.
    4
    policyTypes: a list of rule types that the NetworkPolicy relates to.
    5
    Specifies as Ingress only policyType.
    6
    There are no ingress rules specified. This causes incoming traffic to be dropped to all pods.

  2. Apply the policy by entering the following command: 

    $ oc apply -f deny-by-default.yaml

    Example output

    multinetworkpolicy.k8s.cni.cncf.io/deny-by-default created

18.3.4.4.7. Creating a multi-network policy to allow traffic from external clients

With the deny-by-default policy in place you can proceed to configure a policy that allows traffic from external clients to a pod with the label app=web.

Note

If you log in with a user with the cluster-admin role, then you can create a network policy in any namespace in the cluster.

Follow this procedure to configure a policy that allows external service from the public Internet directly or by using a Load Balancer to access the pod. Traffic is only allowed to a pod with the label app=web.

Prerequisites

  • Your cluster uses a network plugin that supports NetworkPolicy objects, such as the OVN-Kubernetes network plugin, with mode: NetworkPolicy set.
  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with cluster-admin privileges.
  • You are working in the namespace that the multi-network policy applies to.

Procedure

  1. Create a policy that allows traffic from the public Internet directly or by using a load balancer to access the pod. Save the YAML in the web-allow-external.yaml file: 

    apiVersion: k8s.cni.cncf.io/v1beta1
kind: MultiNetworkPolicy
metadata:
  name: web-allow-external
  namespace: default
  annotations:
    k8s.v1.cni.cncf.io/policy-for: <network_name>
spec:
  policyTypes:
  - Ingress
  podSelector:
    matchLabels:
      app: web
  ingress:
    - {}

  2. Apply the policy by entering the following command: 

    $ oc apply -f web-allow-external.yaml

    Example output

    multinetworkpolicy.k8s.cni.cncf.io/web-allow-external created

    This policy allows traffic from all resources, including external traffic as illustrated in the following diagram:

Allow traffic from external clients
18.3.4.4.8. Creating a multi-network policy allowing traffic to an application from all namespaces
Note

If you log in with a user with the cluster-admin role, then you can create a network policy in any namespace in the cluster.

Follow this procedure to configure a policy that allows traffic from all pods in all namespaces to a particular application.

Prerequisites

  • Your cluster uses a network plugin that supports NetworkPolicy objects, such as the OVN-Kubernetes network plugin, with mode: NetworkPolicy set.
  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with cluster-admin privileges.
  • You are working in the namespace that the multi-network policy applies to.

Procedure

  1. Create a policy that allows traffic from all pods in all namespaces to a particular application. Save the YAML in the web-allow-all-namespaces.yaml file: 

    apiVersion: k8s.cni.cncf.io/v1beta1
kind: MultiNetworkPolicy
metadata:
  name: web-allow-all-namespaces
  namespace: default
  annotations:
    k8s.v1.cni.cncf.io/policy-for: <network_name>
spec:
  podSelector:
    matchLabels:
      app: web 1
  policyTypes:
  - Ingress
  ingress:
  - from:
    - namespaceSelector: {} 2
    1
    Applies the policy only to app:web pods in default namespace.
    2
    Selects all pods in all namespaces.
    Note

    By default, if you omit specifying a namespaceSelector it does not select any namespaces, which means the policy allows traffic only from the namespace the network policy is deployed to.

  2. Apply the policy by entering the following command: 

    $ oc apply -f web-allow-all-namespaces.yaml

    Example output

    multinetworkpolicy.k8s.cni.cncf.io/web-allow-all-namespaces created

Verification

  1. Start a web service in the default namespace by entering the following command: 

    $ oc run web --namespace=default --image=nginx --labels="app=web" --expose --port=80

  2. Run the following command to deploy an alpine image in the secondary namespace and to start a shell: 

    $ oc run test-$RANDOM --namespace=secondary --rm -i -t --image=alpine -- sh

  3. Run the following command in the shell and observe that the request is allowed: 

    # wget -qO- --timeout=2 http://web.default

    Expected output

    <!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

18.3.4.4.9. Creating a multi-network policy allowing traffic to an application from a namespace
Note

If you log in with a user with the cluster-admin role, then you can create a network policy in any namespace in the cluster.

Follow this procedure to configure a policy that allows traffic to a pod with the label app=web from a particular namespace. You might want to do this to:

  • Restrict traffic to a production database only to namespaces where production workloads are deployed.
  • Enable monitoring tools deployed to a particular namespace to scrape metrics from the current namespace.

Prerequisites

  • Your cluster uses a network plugin that supports NetworkPolicy objects, such as the OVN-Kubernetes network plugin, with mode: NetworkPolicy set.
  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with cluster-admin privileges.
  • You are working in the namespace that the multi-network policy applies to.

Procedure

  1. Create a policy that allows traffic from all pods in a particular namespaces with a label purpose=production. Save the YAML in the web-allow-prod.yaml file: 

    apiVersion: k8s.cni.cncf.io/v1beta1
kind: MultiNetworkPolicy
metadata:
  name: web-allow-prod
  namespace: default
  annotations:
    k8s.v1.cni.cncf.io/policy-for: <network_name>
spec:
  podSelector:
    matchLabels:
      app: web 1
  policyTypes:
  - Ingress
  ingress:
  - from:
    - namespaceSelector:
        matchLabels:
          purpose: production 2
    1
    Applies the policy only to app:web pods in the default namespace.
    2
    Restricts traffic to only pods in namespaces that have the label purpose=production.

  2. Apply the policy by entering the following command: 

    $ oc apply -f web-allow-prod.yaml

    Example output

    multinetworkpolicy.k8s.cni.cncf.io/web-allow-prod created

Verification

  1. Start a web service in the default namespace by entering the following command: 

    $ oc run web --namespace=default --image=nginx --labels="app=web" --expose --port=80

  2. Run the following command to create the prod namespace: 

    $ oc create namespace prod

  3. Run the following command to label the prod namespace: 

    $ oc label namespace/prod purpose=production

  4. Run the following command to create the dev namespace: 

    $ oc create namespace dev

  5. Run the following command to label the dev namespace: 

    $ oc label namespace/dev purpose=testing

  6. Run the following command to deploy an alpine image in the dev namespace and to start a shell: 

    $ oc run test-$RANDOM --namespace=dev --rm -i -t --image=alpine -- sh

  7. Run the following command in the shell and observe that the request is blocked: 

    # wget -qO- --timeout=2 http://web.default

    Expected output

    wget: download timed out

  8. Run the following command to deploy an alpine image in the prod namespace and start a shell: 

    $ oc run test-$RANDOM --namespace=prod --rm -i -t --image=alpine -- sh

  9. Run the following command in the shell and observe that the request is allowed: 

    # wget -qO- --timeout=2 http://web.default

    Expected output

    <!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

18.3.4.5. Additional resources

18.3.5. Removing a pod from an additional network

As a cluster user you can remove a pod from an additional network.

18.3.5.1. Removing a pod from an additional network

You can remove a pod from an additional network only by deleting the pod.

Prerequisites

  • An additional network is attached to the pod.
  • Install the OpenShift CLI (oc).
  • Log in to the cluster.

Procedure

  • To delete the pod, enter the following command: 

    $ oc delete pod <name> -n <namespace>
    • <name> is the name of the pod.
    • <namespace> is the namespace that contains the pod.

18.3.6. Editing an additional network

As a cluster administrator you can modify the configuration for an existing additional network.

18.3.6.1. Modifying an additional network attachment definition

As a cluster administrator, you can make changes to an existing additional network. Any existing pods attached to the additional network will not be updated.

Prerequisites

  • You have configured an additional network for your cluster.
  • Install the OpenShift CLI (oc).
  • Log in as a user with cluster-admin privileges.

Procedure

To edit an additional network for your cluster, complete the following steps:

  1. Run the following command to edit the Cluster Network Operator (CNO) CR in your default text editor: 

    $ oc edit networks.operator.openshift.io cluster
  2. In the additionalNetworks collection, update the additional network with your changes.
  3. Save your changes and quit the text editor to commit your changes.

  4. Optional: Confirm that the CNO updated the NetworkAttachmentDefinition object by running the following command. Replace <network-name> with the name of the additional network to display. There might be a delay before the CNO updates the NetworkAttachmentDefinition object to reflect your changes. 

    $ oc get network-attachment-definitions <network-name> -o yaml

    For example, the following console output displays a NetworkAttachmentDefinition object that is named net1: 

    $ oc get network-attachment-definitions net1 -o go-template='{{printf "%s\n" .spec.config}}'
{ "cniVersion": "0.3.1", "type": "macvlan",
"master": "ens5",
"mode": "bridge",
"ipam":       {"type":"static","routes":[{"dst":"0.0.0.0/0","gw":"10.128.2.1"}],"addresses":[{"address":"10.128.2.100/23","gateway":"10.128.2.1"}],"dns":{"nameservers":["172.30.0.10"],"domain":"us-west-2.compute.internal","search":["us-west-2.compute.internal"]}} }

18.3.7. Configuring IP address assignment on secondary networks

The following sections provide instructions and information for how to configure IP address assignments for secondary networks.

18.3.7.1. Configuration of IP address assignment for an additional network

The IP address management (IPAM) Container Network Interface (CNI) plugin provides IP addresses for other CNI plugins.

You can use the following IP address assignment types:

  • Static assignment.
  • Dynamic assignment through a DHCP server. The DHCP server you specify must be reachable from the additional network.
  • Dynamic assignment through the Whereabouts IPAM CNI plugin.
18.3.7.1.1. Static IP address assignment configuration

The following table describes the configuration for static IP address assignment:

Table 18.11. ipam static configuration object
FieldTypeDescription

type

string

The IPAM address type. The value static is required.

addresses

array

An array of objects specifying IP addresses to assign to the virtual interface. Both IPv4 and IPv6 IP addresses are supported.

routes

array

An array of objects specifying routes to configure inside the pod.

dns

array

Optional: An array of objects specifying the DNS configuration.

The addresses array requires objects with the following fields:

Table 18.12. ipam.addresses[] array
FieldTypeDescription

address

string

An IP address and network prefix that you specify. For example, if you specify 10.10.21.10/24, then the additional network is assigned an IP address of 10.10.21.10 and the netmask is 255.255.255.0.

gateway

string

The default gateway to route egress network traffic to.

Table 18.13. ipam.routes[] array
FieldTypeDescription

dst

string

The IP address range in CIDR format, such as 192.168.17.0/24 or 0.0.0.0/0 for the default route.

gw

string

The gateway where network traffic is routed.

Table 18.14. ipam.dns object
FieldTypeDescription

nameservers

array

An array of one or more IP addresses for to send DNS queries to.

domain

array

The default domain to append to a hostname. For example, if the domain is set to example.com, a DNS lookup query for example-host is rewritten as example-host.example.com.

search

array

An array of domain names to append to an unqualified hostname, such as example-host, during a DNS lookup query.

Static IP address assignment configuration example

{
  "ipam": {
    "type": "static",
      "addresses": [
        {
          "address": "191.168.1.7/24"
        }
      ]
  }
}

18.3.7.1.2. Dynamic IP address (DHCP) assignment configuration

The following JSON describes the configuration for dynamic IP address address assignment with DHCP.

Renewal of DHCP leases

A pod obtains its original DHCP lease when it is created. The lease must be periodically renewed by a minimal DHCP server deployment running on the cluster.

To trigger the deployment of the DHCP server, you must create a shim network attachment by editing the Cluster Network Operator configuration, as in the following example:

Example shim network attachment definition

apiVersion: operator.openshift.io/v1
kind: Network
metadata:
  name: cluster
spec:
  additionalNetworks:
  - name: dhcp-shim
    namespace: default
    type: Raw
    rawCNIConfig: |-
      {
        "name": "dhcp-shim",
        "cniVersion": "0.3.1",
        "type": "bridge",
        "ipam": {
          "type": "dhcp"
        }
      }
  # ...

Table 18.15. ipam DHCP configuration object
FieldTypeDescription

type

string

The IPAM address type. The value dhcp is required.

Dynamic IP address (DHCP) assignment configuration example

{
  "ipam": {
    "type": "dhcp"
  }
}

18.3.7.1.3. Dynamic IP address assignment configuration with Whereabouts

The Whereabouts CNI plugin allows the dynamic assignment of an IP address to an additional network without the use of a DHCP server.

The Whereabouts CNI plugin also supports overlapping IP address ranges and configuration of the same CIDR range multiple times within separate NetworkAttachmentDefinition CRDs. This provides greater flexibility and management capabilities in multi-tenant environments.

18.3.7.1.3.1. Dynamic IP address configuration objects

The following table describes the configuration objects for dynamic IP address assignment with Whereabouts:

Table 18.16. ipam whereabouts configuration object
FieldTypeDescription

type

string

The IPAM address type. The value whereabouts is required.

range

string

An IP address and range in CIDR notation. IP addresses are assigned from within this range of addresses.

exclude

array

Optional: A list of zero or more IP addresses and ranges in CIDR notation. IP addresses within an excluded address range are not assigned.

network_name

string

Optional: Helps ensure that each group or domain of pods gets its own set of IP addresses, even if they share the same range of IP addresses. Setting this field is important for keeping networks separate and organized, notably in multi-tenant environments.

18.3.7.1.3.2. Dynamic IP address assignment configuration that uses Whereabouts

The following example shows a dynamic address assignment configuration that uses Whereabouts:

Whereabouts dynamic IP address assignment

{
  "ipam": {
    "type": "whereabouts",
    "range": "192.0.2.192/27",
    "exclude": [
       "192.0.2.192/30",
       "192.0.2.196/32"
    ]
  }
}

18.3.7.1.3.3. Dynamic IP address assignment that uses Whereabouts with overlapping IP address ranges

The following example shows a dynamic IP address assignment that uses overlapping IP address ranges for multi-tenant networks.

NetworkAttachmentDefinition 1

{
  "ipam": {
    "type": "whereabouts",
    "range": "192.0.2.192/29",
    "network_name": "example_net_common", 1
  }
}

1
Optional. If set, must match the network_name of NetworkAttachmentDefinition 2.

NetworkAttachmentDefinition 2

{
  "ipam": {
    "type": "whereabouts",
    "range": "192.0.2.192/24",
    "network_name": "example_net_common", 1
  }
}

1
Optional. If set, must match the network_name of NetworkAttachmentDefinition 1.
18.3.7.1.4. Creating a whereabouts-reconciler daemon set

The Whereabouts reconciler is responsible for managing dynamic IP address assignments for the pods within a cluster by using the Whereabouts IP Address Management (IPAM) solution. It ensures that each pod gets a unique IP address from the specified IP address range. It also handles IP address releases when pods are deleted or scaled down.

Note

You can also use a NetworkAttachmentDefinition custom resource definition (CRD) for dynamic IP address assignment.

The whereabouts-reconciler daemon set is automatically created when you configure an additional network through the Cluster Network Operator. It is not automatically created when you configure an additional network from a YAML manifest.

To trigger the deployment of the whereabouts-reconciler daemon set, you must manually create a whereabouts-shim network attachment by editing the Cluster Network Operator custom resource (CR) file.

Use the following procedure to deploy the whereabouts-reconciler daemon set.

Procedure

  1. Edit the Network.operator.openshift.io custom resource (CR) by running the following command: 

    $ oc edit network.operator.openshift.io cluster

  2. Include the additionalNetworks section shown in this example YAML extract within the spec definition of the custom resource (CR): 

    apiVersion: operator.openshift.io/v1
kind: Network
metadata:
  name: cluster
# ...
spec:
  additionalNetworks:
  - name: whereabouts-shim
    namespace: default
    rawCNIConfig: |-
      {
       "name": "whereabouts-shim",
       "cniVersion": "0.3.1",
       "type": "bridge",
       "ipam": {
         "type": "whereabouts"
       }
      }
    type: Raw
# ...
  3. Save the file and exit the text editor.

  4. Verify that the whereabouts-reconciler daemon set deployed successfully by running the following command: 

    $ oc get all -n openshift-multus | grep whereabouts-reconciler

    Example output

    pod/whereabouts-reconciler-jnp6g 1/1 Running 0 6s
pod/whereabouts-reconciler-k76gg 1/1 Running 0 6s
pod/whereabouts-reconciler-k86t9 1/1 Running 0 6s
pod/whereabouts-reconciler-p4sxw 1/1 Running 0 6s
pod/whereabouts-reconciler-rvfdv 1/1 Running 0 6s
pod/whereabouts-reconciler-svzw9 1/1 Running 0 6s
daemonset.apps/whereabouts-reconciler 6 6 6 6 6 kubernetes.io/os=linux 6s

18.3.7.1.5. Configuring the Whereabouts IP reconciler schedule

The Whereabouts IPAM CNI plugin runs the IP reconciler daily. This process cleans up any stranded IP allocations that might result in exhausting IPs and therefore prevent new pods from getting an IP allocated to them.

Use this procedure to change the frequency at which the IP reconciler runs.

Prerequisites

  • You installed the OpenShift CLI (oc).
  • You have access to the cluster as a user with the cluster-admin role.
  • You have deployed the whereabouts-reconciler daemon set, and the whereabouts-reconciler pods are up and running.

Procedure

  1. Run the following command to create a ConfigMap object named whereabouts-config in the openshift-multus namespace with a specific cron expression for the IP reconciler: 

    $ oc create configmap whereabouts-config -n openshift-multus --from-literal=reconciler_cron_expression="*/15 * * * *"

    This cron expression indicates the IP reconciler runs every 15 minutes. Adjust the expression based on your specific requirements.

    Note

    The whereabouts-reconciler daemon set can only consume a cron expression pattern that includes five asterisks. The sixth, which is used to denote seconds, is currently not supported.

  2. Retrieve information about resources related to the whereabouts-reconciler daemon set and pods within the openshift-multus namespace by running the following command: 

    $ oc get all -n openshift-multus | grep whereabouts-reconciler

    Example output

    pod/whereabouts-reconciler-2p7hw                   1/1     Running   0             4m14s
pod/whereabouts-reconciler-76jk7                   1/1     Running   0             4m14s
pod/whereabouts-reconciler-94zw6                   1/1     Running   0             4m14s
pod/whereabouts-reconciler-mfh68                   1/1     Running   0             4m14s
pod/whereabouts-reconciler-pgshz                   1/1     Running   0             4m14s
pod/whereabouts-reconciler-xn5xz                   1/1     Running   0             4m14s
daemonset.apps/whereabouts-reconciler          6         6         6       6            6           kubernetes.io/os=linux   4m16s

  3. Run the following command to verify that the whereabouts-reconciler pod runs the IP reconciler with the configured interval: 

    $ oc -n openshift-multus logs whereabouts-reconciler-2p7hw

    Example output

    2024-02-02T16:33:54Z [debug] event not relevant: "/cron-schedule/..2024_02_02_16_33_54.1375928161": CREATE
2024-02-02T16:33:54Z [debug] event not relevant: "/cron-schedule/..2024_02_02_16_33_54.1375928161": CHMOD
2024-02-02T16:33:54Z [debug] event not relevant: "/cron-schedule/..data_tmp": RENAME
2024-02-02T16:33:54Z [verbose] using expression: */15 * * * *
2024-02-02T16:33:54Z [verbose] configuration updated to file "/cron-schedule/..data". New cron expression: */15 * * * *
2024-02-02T16:33:54Z [verbose] successfully updated CRON configuration id "00c2d1c9-631d-403f-bb86-73ad104a6817" - new cron expression: */15 * * * *
2024-02-02T16:33:54Z [debug] event not relevant: "/cron-schedule/config": CREATE
2024-02-02T16:33:54Z [debug] event not relevant: "/cron-schedule/..2024_02_02_16_26_17.3874177937": REMOVE
2024-02-02T16:45:00Z [verbose] starting reconciler run
2024-02-02T16:45:00Z [debug] NewReconcileLooper - inferred connection data
2024-02-02T16:45:00Z [debug] listing IP pools
2024-02-02T16:45:00Z [debug] no IP addresses to cleanup
2024-02-02T16:45:00Z [verbose] reconciler success

18.3.7.1.6. Creating a configuration for assignment of dual-stack IP addresses dynamically

Dual-stack IP address assignment can be configured with the ipRanges parameter for:

  • IPv4 addresses
  • IPv6 addresses
  • multiple IP address assignment

Procedure

  1. Set type to whereabouts.

  2. Use ipRanges to allocate IP addresses as shown in the following example: 

    cniVersion: operator.openshift.io/v1
kind: Network
=metadata:
  name: cluster
spec:
  additionalNetworks:
  - name: whereabouts-shim
    namespace: default
    type: Raw
    rawCNIConfig: |-
      {
       "name": "whereabouts-dual-stack",
       "cniVersion": "0.3.1,
       "type": "bridge",
       "ipam": {
         "type": "whereabouts",
         "ipRanges": [
                  {"range": "192.168.10.0/24"},
                  {"range": "2001:db8::/64"}
              ]
       }
      }
  3. Attach network to a pod. For more information, see "Adding a pod to an additional network".
  4. Verify that all IP addresses are assigned.

  5. Run the following command to ensure the IP addresses are assigned as metadata. 

    $ oc exec -it mypod -- ip a

18.3.8. Configuring the master interface in the container network namespace

The following section provides instructions and information for how to create and manage a MAC-VLAN, IP-VLAN, and VLAN subinterface based on a master interface.

18.3.8.1. About configuring the master interface in the container network namespace

You can create a MAC-VLAN, an IP-VLAN, or a VLAN subinterface that is based on a master interface that exists in a container namespace. You can also create a master interface as part of the pod network configuration in a separate network attachment definition CRD.

To use a container namespace master interface, you must specify true for the linkInContainer parameter that exists in the subinterface configuration of the NetworkAttachmentDefinition CRD.

18.3.8.1.1. Creating multiple VLANs on SR-IOV VFs

An example use case for utilizing this feature is to create multiple VLANs based on SR-IOV VFs. To do so, begin by creating an SR-IOV network and then define the network attachments for the VLAN interfaces.

The following example shows how to configure the setup illustrated in this diagram.

Figure 18.1. Creating VLANs

Creating VLANs

Prerequisites

  • You installed the OpenShift CLI (oc).
  • You have access to the cluster as a user with the cluster-admin role.
  • You have installed the SR-IOV Network Operator.

Procedure

  1. Create a dedicated container namespace where you want to deploy your pod by using the following command: 

    $ oc new-project test-namespace

  2. Create an SR-IOV node policy:

    1. Create an SriovNetworkNodePolicy object, and then save the YAML in the sriov-node-network-policy.yaml file: 

      apiVersion: sriovnetwork.openshift.io/v1
kind: SriovNetworkNodePolicy
metadata:
 name: sriovnic
 namespace: openshift-sriov-network-operator
spec:
 deviceType: netdevice
 isRdma: false
 needVhostNet: true
 nicSelector:
   vendor: "15b3" 1
   deviceID: "101b" 2
   rootDevices: ["00:05.0"]
 numVfs: 10
 priority: 99
 resourceName: sriovnic
 nodeSelector:
    feature.node.kubernetes.io/network-sriov.capable: "true"
      Note

      The SR-IOV network node policy configuration example, with the setting deviceType: netdevice, is tailored specifically for Mellanox Network Interface Cards (NICs).

      1
      The vendor hexadecimal code of the SR-IOV network device. The value 15b3 is associated with a Mellanox NIC.
      2
      The device hexadecimal code of the SR-IOV network device.

    2. Apply the YAML by running the following command: 

      $ oc apply -f sriov-node-network-policy.yaml
      Note

      Applying this might take some time due to the node requiring a reboot.

  3. Create an SR-IOV network:

    1. Create the SriovNetwork custom resource (CR) for the additional SR-IOV network attachment as in the following example CR. Save the YAML as the file sriov-network-attachment.yaml: 

      apiVersion: sriovnetwork.openshift.io/v1
kind: SriovNetwork
metadata:
 name: sriov-network
 namespace: openshift-sriov-network-operator
spec:
 networkNamespace: test-namespace
 resourceName: sriovnic
 spoofChk: "off"
 trust: "on"

    2. Apply the YAML by running the following command: 

      $ oc apply -f sriov-network-attachment.yaml

  4. Create the VLAN additional network:

    1. Using the following YAML example, create a file named vlan100-additional-network-configuration.yaml: 

      apiVersion: k8s.cni.cncf.io/v1
kind: NetworkAttachmentDefinition
metadata:
  name: vlan-100
  namespace: test-namespace
spec:
  config: |
    {
      "cniVersion": "0.4.0",
      "name": "vlan-100",
      "plugins": [
        {
          "type": "vlan",
          "master": "ext0", 1
          "mtu": 1500,
          "vlanId": 100,
          "linkInContainer": true, 2
          "ipam": {"type": "whereabouts", "ipRanges": [{"range": "1.1.1.0/24"}]}
        }
      ]
    }
      1
      The VLAN configuration needs to specify the master name. This can be configured in the pod networks annotation.
      2
      The linkInContainer parameter must be specified.

    2. Apply the YAML file by running the following command: 

      $ oc apply -f vlan100-additional-network-configuration.yaml

  5. Create a pod definition by using the earlier specified networks:

    1. Using the following YAML example, create a file named pod-a.yaml file:

      Note

      The manifest below includes 2 resources:

      • Namespace with security labels
      • Pod definition with appropriate network annotation 
      apiVersion: v1
kind: Namespace
metadata:
  name: test-namespace
  labels:
    pod-security.kubernetes.io/enforce: privileged
    pod-security.kubernetes.io/audit: privileged
    pod-security.kubernetes.io/warn: privileged
    security.openshift.io/scc.podSecurityLabelSync: "false"
---
apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  namespace: test-namespace
  annotations:
    k8s.v1.cni.cncf.io/networks: '[
      {
        "name": "sriov-network",
        "namespace": "test-namespace",
        "interface": "ext0" 1
      },
      {
        "name": "vlan-100",
        "namespace": "test-namespace",
        "interface": "ext0.100"
      }
    ]'
spec:
  securityContext:
    runAsNonRoot: true
  containers:
    - name: nginx-container
      image: nginxinc/nginx-unprivileged:latest
      securityContext:
        allowPrivilegeEscalation: false
        capabilities:
          drop: ["ALL"]
      ports:
        - containerPort: 80
      seccompProfile:
        type: "RuntimeDefault"
      1
      The name to be used as the master for the VLAN interface.

    2. Apply the YAML file by running the following command: 

      $ oc apply -f pod-a.yaml

  6. Get detailed information about the nginx-pod within the test-namespace by running the following command: 

    $ oc describe pods nginx-pod -n test-namespace

    Example output

    Name:         nginx-pod
Namespace:    test-namespace
Priority:     0
Node:         worker-1/10.46.186.105
Start Time:   Mon, 14 Aug 2023 16:23:13 -0400
Labels:       <none>
Annotations:  k8s.ovn.org/pod-networks:
                {"default":{"ip_addresses":["10.131.0.26/23"],"mac_address":"0a:58:0a:83:00:1a","gateway_ips":["10.131.0.1"],"routes":[{"dest":"10.128.0.0...
              k8s.v1.cni.cncf.io/network-status:
                [{
                    "name": "ovn-kubernetes",
                    "interface": "eth0",
                    "ips": [
                        "10.131.0.26"
                    ],
                    "mac": "0a:58:0a:83:00:1a",
                    "default": true,
                    "dns": {}
                },{
                    "name": "test-namespace/sriov-network",
                    "interface": "ext0",
                    "mac": "6e:a7:5e:3f:49:1b",
                    "dns": {},
                    "device-info": {
                        "type": "pci",
                        "version": "1.0.0",
                        "pci": {
                            "pci-address": "0000:d8:00.2"
                        }
                    }
                },{
                    "name": "test-namespace/vlan-100",
                    "interface": "ext0.100",
                    "ips": [
                        "1.1.1.1"
                    ],
                    "mac": "6e:a7:5e:3f:49:1b",
                    "dns": {}
                }]
              k8s.v1.cni.cncf.io/networks:
                [ { "name": "sriov-network", "namespace": "test-namespace", "interface": "ext0" }, { "name": "vlan-100", "namespace": "test-namespace", "i...
              openshift.io/scc: privileged
Status:       Running
IP:           10.131.0.26
IPs:
  IP:  10.131.0.26

18.3.8.1.2. Creating a subinterface based on a bridge master interface in a container namespace

You can create a subinterface based on a bridge master interface that exists in a container namespace. Creating a subinterface can be applied to other types of interfaces.

Prerequisites

  • You have installed the OpenShift CLI (oc).
  • You are logged in to the OpenShift Container Platform cluster as a user with cluster-admin privileges.

Procedure

  1. Create a dedicated container namespace where you want to deploy your pod by entering the following command: 

    $ oc new-project test-namespace

  2. Using the following YAML example, create a bridge NetworkAttachmentDefinition custom resource definition (CRD) file named bridge-nad.yaml: 

    apiVersion: "k8s.cni.cncf.io/v1"
kind: NetworkAttachmentDefinition
metadata:
  name: bridge-network
spec:
  config: '{
    "cniVersion": "0.4.0",
    "name": "bridge-network",
    "type": "bridge",
    "bridge": "br-001",
    "isGateway": true,
    "ipMasq": true,
    "hairpinMode": true,
    "ipam": {
      "type": "host-local",
      "subnet": "10.0.0.0/24",
      "routes": [{"dst": "0.0.0.0/0"}]
    }
  }'

  3. Run the following command to apply the NetworkAttachmentDefinition CRD to your OpenShift Container Platform cluster: 

    $ oc apply -f bridge-nad.yaml

  4. Verify that you successfully created a NetworkAttachmentDefinition CRD by entering the following command: 

    $ oc get network-attachment-definitions

    Example output

    NAME             AGE
bridge-network   15s

  5. Using the following YAML example, create a file named ipvlan-additional-network-configuration.yaml for the IPVLAN additional network configuration: 

    apiVersion: k8s.cni.cncf.io/v1
kind: NetworkAttachmentDefinition
metadata:
  name: ipvlan-net
  namespace: test-namespace
spec:
  config: '{
    "cniVersion": "0.3.1",
    "name": "ipvlan-net",
    "type": "ipvlan",
    "master": "ext0", 1
    "mode": "l3",
    "linkInContainer": true, 2
    "ipam": {"type": "whereabouts", "ipRanges": [{"range": "10.0.0.0/24"}]}
  }'
    1
    Specifies the ethernet interface to associate with the network attachment. This is subsequently configured in the pod networks annotation.
    2
    Specifies that the master interface is in the container network namespace.

  6. Apply the YAML file by running the following command: 

    $ oc apply -f ipvlan-additional-network-configuration.yaml

  7. Verify that the NetworkAttachmentDefinition CRD has been created successfully by running the following command: 

    $ oc get network-attachment-definitions

    Example output

    NAME             AGE
bridge-network   87s
ipvlan-net       9s

  8. Using the following YAML example, create a file named pod-a.yaml for the pod definition: 

    apiVersion: v1
kind: Pod
metadata:
  name: pod-a
  namespace: test-namespace
  annotations:
    k8s.v1.cni.cncf.io/networks: '[
      {
        "name": "bridge-network",
        "interface": "ext0" 1
      },
      {
        "name": "ipvlan-net",
        "interface": "ext1"
      }
    ]'
spec:
  securityContext:
    runAsNonRoot: true
    seccompProfile:
      type: RuntimeDefault
  containers:
  - name: test-pod
    image: quay.io/openshifttest/hello-sdn@sha256:c89445416459e7adea9a5a416b3365ed3d74f2491beb904d61dc8d1eb89a72a4
    securityContext:
      allowPrivilegeEscalation: false
      capabilities:
        drop: [ALL]
    1
    Specifies the name to be used as the master for the IPVLAN interface.

  9. Apply the YAML file by running the following command: 

    $ oc apply -f pod-a.yaml

  10. Verify that the pod is running by using the following command: 

    $ oc get pod -n test-namespace

    Example output

    NAME    READY   STATUS    RESTARTS   AGE
pod-a   1/1     Running   0          2m36s

  11. Show network interface information about the pod-a resource within the test-namespace by running the following command: 

    $ oc exec -n test-namespace pod-a -- ip a

    Example output

    1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
3: eth0@if105: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1400 qdisc noqueue state UP group default
    link/ether 0a:58:0a:d9:00:5d brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 10.217.0.93/23 brd 10.217.1.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::488b:91ff:fe84:a94b/64 scope link
       valid_lft forever preferred_lft forever
4: ext0@if107: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default
    link/ether be:da:bd:7e:f4:37 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 10.0.0.2/24 brd 10.0.0.255 scope global ext0
       valid_lft forever preferred_lft forever
    inet6 fe80::bcda:bdff:fe7e:f437/64 scope link
       valid_lft forever preferred_lft forever
5: ext1@ext0: <BROADCAST,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default
    link/ether be:da:bd:7e:f4:37 brd ff:ff:ff:ff:ff:ff
    inet 10.0.0.1/24 brd 10.0.0.255 scope global ext1
       valid_lft forever preferred_lft forever
    inet6 fe80::beda:bd00:17e:f437/64 scope link
       valid_lft forever preferred_lft forever

    This output shows that the network interface ext1 is associated with the physical interface ext0.

18.3.9. Removing an additional network

As a cluster administrator you can remove an additional network attachment.

18.3.9.1. Removing an additional network attachment definition

As a cluster administrator, you can remove an additional network from your OpenShift Container Platform cluster. The additional network is not removed from any pods it is attached to.

Prerequisites

  • Install the OpenShift CLI (oc).
  • Log in as a user with cluster-admin privileges.

Procedure

To remove an additional network from your cluster, complete the following steps:

  1. Edit the Cluster Network Operator (CNO) in your default text editor by running the following command: 

    $ oc edit networks.operator.openshift.io cluster

  2. Modify the CR by removing the configuration from the additionalNetworks collection for the network attachment definition you are removing. 

    apiVersion: operator.openshift.io/v1
kind: Network
metadata:
  name: cluster
spec:
  additionalNetworks: [] 1
    1
    If you are removing the configuration mapping for the only additional network attachment definition in the additionalNetworks collection, you must specify an empty collection.
  3. Save your changes and quit the text editor to commit your changes.

  4. Optional: Confirm that the additional network CR was deleted by running the following command: 

    $ oc get network-attachment-definition --all-namespaces

18.4. Virtual routing and forwarding

18.4.1. About virtual routing and forwarding

Virtual routing and forwarding (VRF) devices combined with IP rules provide the ability to create virtual routing and forwarding domains. VRF reduces the number of permissions needed by CNF, and provides increased visibility of the network topology of secondary networks. VRF is used to provide multi-tenancy functionality, for example, where each tenant has its own unique routing tables and requires different default gateways.

Processes can bind a socket to the VRF device. Packets through the binded socket use the routing table associated with the VRF device. An important feature of VRF is that it impacts only OSI model layer 3 traffic and above so L2 tools, such as LLDP, are not affected. This allows higher priority IP rules such as policy based routing to take precedence over the VRF device rules directing specific traffic.

18.4.1.1. Benefits of secondary networks for pods for telecommunications operators

In telecommunications use cases, each CNF can potentially be connected to multiple different networks sharing the same address space. These secondary networks can potentially conflict with the cluster’s main network CIDR. Using the CNI VRF plugin, network functions can be connected to different customers' infrastructure using the same IP address, keeping different customers isolated. IP addresses are overlapped with OpenShift Container Platform IP space. The CNI VRF plugin also reduces the number of permissions needed by CNF and increases the visibility of network topologies of secondary networks.

18.5. Assigning a secondary network to a VRF

As a cluster administrator, you can configure an additional network for a virtual routing and forwarding (VRF) domain by using the CNI VRF plugin. The virtual network that this plugin creates is associated with the physical interface that you specify.

Using a secondary network with a VRF instance has the following advantages:

Workload isolation
Isolate workload traffic by configuring a VRF instance for the additional network.
Improved security
Enable improved security through isolated network paths in the VRF domain.
Multi-tenancy support
Support multi-tenancy through network segmentation with a unique routing table in the VRF domain for each tenant.
Note

Applications that use VRFs must bind to a specific device. The common usage is to use the SO_BINDTODEVICE option for a socket. The SO_BINDTODEVICE option binds the socket to the device that is specified in the passed interface name, for example, eth1. To use the SO_BINDTODEVICE option, the application must have CAP_NET_RAW capabilities.

Using a VRF through the ip vrf exec command is not supported in OpenShift Container Platform pods. To use VRF, bind applications directly to the VRF interface.

Additional resources

18.5.1. Creating an additional network attachment with the CNI VRF plugin

The Cluster Network Operator (CNO) manages additional network definitions. When you specify an additional network to create, the CNO creates the NetworkAttachmentDefinition custom resource (CR) automatically.

Note

Do not edit the NetworkAttachmentDefinition CRs that the Cluster Network Operator manages. Doing so might disrupt network traffic on your additional network.

To create an additional network attachment with the CNI VRF plugin, perform the following procedure.

Prerequisites

  • Install the OpenShift Container Platform CLI (oc).
  • Log in to the OpenShift cluster as a user with cluster-admin privileges.

Procedure

  1. Create the Network custom resource (CR) for the additional network attachment and insert the rawCNIConfig configuration for the additional network, as in the following example CR. Save the YAML as the file additional-network-attachment.yaml. 

    apiVersion: operator.openshift.io/v1
kind: Network
metadata:
  name: cluster
spec:
  additionalNetworks:
    - name: test-network-1
      namespace: additional-network-1
      type: Raw
      rawCNIConfig: '{
        "cniVersion": "0.3.1",
        "name": "macvlan-vrf",
        "plugins": [  1
        {
          "type": "macvlan",
          "master": "eth1",
          "ipam": {
              "type": "static",
              "addresses": [
              {
                  "address": "191.168.1.23/24"
              }
              ]
          }
        },
        {
          "type": "vrf", 2
          "vrfname": "vrf-1",  3
          "table": 1001   4
        }]
      }'
    1
    plugins must be a list. The first item in the list must be the secondary network underpinning the VRF network. The second item in the list is the VRF plugin configuration.
    2
    type must be set to vrf.
    3
    vrfname is the name of the VRF that the interface is assigned to. If it does not exist in the pod, it is created.
    4
    Optional. table is the routing table ID. By default, the tableid parameter is used. If it is not specified, the CNI assigns a free routing table ID to the VRF.
    Note

    VRF functions correctly only when the resource is of type netdevice.

  2. Create the Network resource: 

    $ oc create -f additional-network-attachment.yaml

  3. Confirm that the CNO created the NetworkAttachmentDefinition CR by running the following command. Replace <namespace> with the namespace that you specified when configuring the network attachment, for example, additional-network-1. 

    $ oc get network-attachment-definitions -n <namespace>

    Example output

    NAME                       AGE
additional-network-1       14m

    Note

    There might be a delay before the CNO creates the CR.

Verification

  1. Create a pod and assign it to the additional network with the VRF instance:

    1. Create a YAML file that defines the Pod resource:

      Example pod-additional-net.yaml file

      apiVersion: v1
kind: Pod
metadata:
 name: pod-additional-net
 annotations:
   k8s.v1.cni.cncf.io/networks: '[
       {
               "name": "test-network-1" 1
       }
 ]'
spec:
 containers:
 - name: example-pod-1
   command: ["/bin/bash", "-c", "sleep 9000000"]
   image: centos:8

      1
      Specify the name of the additional network with the VRF instance.

    2. Create the Pod resource by running the following command: 

      $ oc create -f pod-additional-net.yaml

      Example output

      pod/test-pod created

  2. Verify that the pod network attachment is connected to the VRF additional network. Start a remote session with the pod and run the following command: 

    $ ip vrf show

    Example output

    Name              Table
-----------------------
vrf-1             1001

  3. Confirm that the VRF interface is the controller for the additional interface: 

    $ ip link

    Example output

    5: net1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master red state UP mode

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