Cluster Network Operator in OKD

Cluster Network Operator in OKD

The Cluster Network Operator (CNO) deploys and manages the cluster network components on an OKD cluster, including the Container Network Interface (CNI) default network provider plug-in selected for the cluster during installation.

Cluster Network Operator

The Cluster Network Operator implements the network API from the operator.openshift.io API group. The Operator deploys the OpenShift SDN default Container Network Interface (CNI) network provider plug-in, or the default network provider plug-in that you selected during cluster installation, by using a daemon set.

Procedure

The Cluster Network Operator is deployed during installation as a Kubernetes Deployment.

Run the following command to view the Deployment status:

$ oc get -n openshift-network-operator deployment/network-operator

Example output

NAME               READY   UP-TO-DATE   AVAILABLE   AGE
network-operator   1/1     1            1           56m

Run the following command to view the state of the Cluster Network Operator:
```
$ oc get clusteroperator/network
```
Example output
```
NAME      VERSION   AVAILABLE   PROGRESSING   DEGRADED   SINCE
network   4.5.4     True        False         False      50m
```
The following fields provide information about the status of the operator: AVAILABLE, PROGRESSING, and DEGRADED. The AVAILABLE field is True when the Cluster Network Operator reports an available status condition.

Viewing the cluster network configuration

Every new OKD installation has a network.config object named cluster.

Procedure

Use the oc describe command to view the cluster network configuration:

$ oc describe network.config/cluster

Example output

Name:         cluster
Namespace:
Labels:       <none>
Annotations:  <none>
API Version:  config.openshift.io/v1
Kind:         Network
Metadata:
  Self Link:           /apis/config.openshift.io/v1/networks/cluster
Spec: (1)
  Cluster Network:
    Cidr:         10.128.0.0/14
    Host Prefix:  23
  Network Type:   OpenShiftSDN
  Service Network:
    172.30.0.0/16
Status: (2)
  Cluster Network:
    Cidr:               10.128.0.0/14
    Host Prefix:        23
  Cluster Network MTU:  8951
  Network Type:         OpenShiftSDN
  Service Network:
    172.30.0.0/16
Events:  <none>

1	The `Spec` field displays the configured state of the cluster network.
2	The `Status` field displays the current state of the cluster network configuration.

Viewing Cluster Network Operator status

You can inspect the status and view the details of the Cluster Network Operator using the oc describe command.

Procedure

Run the following command to view the status of the Cluster Network Operator:
```
$ oc describe clusteroperators/network
```

Viewing Cluster Network Operator logs

You can view Cluster Network Operator logs by using the oc logs command.

Procedure

Run the following command to view the logs of the Cluster Network Operator:

$ oc logs --namespace=openshift-network-operator deployment/network-operator

Cluster Network Operator configuration

The configuration for the cluster network is specified as part of the Cluster Network Operator (CNO) configuration and stored in a custom resource (CR) object that is named cluster. The CR specifies the fields for the Network API in the operator.openshift.io API group.

The CNO configuration inherits the following fields during cluster installation from the Network API in the Network.config.openshift.io API group and these fields cannot be changed:

clusterNetwork

IP address pools from which pod IP addresses are allocated.

serviceNetwork

IP address pool for services.

defaultNetwork.type

Cluster network provider, such as OpenShift SDN or OVN-Kubernetes.

After cluster installation, you cannot modify the fields listed in the previous section.

You can specify the cluster network provider configuration for your cluster by setting the fields for the defaultNetwork object in the CNO object named cluster.

Cluster Network Operator configuration object

The fields for the Cluster Network Operator (CNO) are described in the following table:

Table 1. Cluster Network Operator configuration object
Field	Type	Description
`metadata.name`	`string`	The name of the CNO object. This name is always `cluster`.
`spec.clusterNetwork`	`array`	A list specifying the blocks of IP addresses from which pod IP addresses are allocated and the subnet prefix length assigned to each individual node in the cluster. For example: `spec:` `clusterNetwork:` `- cidr: 10.128.0.0/19` `hostPrefix: 23` `- cidr: 10.128.32.0/19` `hostPrefix: 23` This value is ready-only and inherited from the `Network.config.openshift.io` object named `cluster` during cluster installation.
`spec.serviceNetwork`	`array`	A block of IP addresses for services. The OpenShift SDN and OVN-Kubernetes Container Network Interface (CNI) network providers support only a single IP address block for the service network. For example: `spec:` `serviceNetwork:` `- 172.30.0.0/14` This value is ready-only and inherited from the `Network.config.openshift.io` object named `cluster` during cluster installation.
`spec.defaultNetwork`	`object`	Configures the Container Network Interface (CNI) cluster network provider for the cluster network.
`spec.kubeProxyConfig`	`object`	The fields for this object specify the kube-proxy configuration. If you are using the OVN-Kubernetes cluster network provider, the kube-proxy configuration has no effect.

defaultNetwork object configuration

The values for the defaultNetwork object are defined in the following table:

Field Type Description

type

string

Either OpenShiftSDN or OVNKubernetes. The cluster network provider is selected during installation. This value cannot be changed after cluster installation.

OKD uses the OVN-Kubernetes Container Network Interface (CNI) cluster network provider by default.

openshiftSDNConfig

object

This object is only valid for the OpenShift SDN cluster network provider.

ovnKubernetesConfig

object

This object is only valid for the OVN-Kubernetes cluster network provider.

Configuration for the OpenShift SDN CNI cluster network provider

The following table describes the configuration fields for the OpenShift SDN Container Network Interface (CNI) cluster network provider.

Table 3. `openshiftSDNConfig` object
Field	Type	Description
`mode`	`string`	The network isolation mode for OpenShift SDN.
`mtu`	`integer`	The maximum transmission unit (MTU) for the VXLAN overlay network. This value is normally configured automatically.
`vxlanPort`	`integer`	The port to use for all VXLAN packets. The default value is `4789`.

You can only change the configuration for your cluster network provider during cluster installation.

Example OpenShift SDN configuration

defaultNetwork:
  type: OpenShiftSDN
  openshiftSDNConfig:
    mode: NetworkPolicy
    mtu: 1450
    vxlanPort: 4789

Configuration for the OVN-Kubernetes CNI cluster network provider

The following table describes the configuration fields for the OVN-Kubernetes CNI cluster network provider.

Table 4. `ovnKubernetesConfig` object
Field	Type	Description
`mtu`	`integer`	The maximum transmission unit (MTU) for the Geneve (Generic Network Virtualization Encapsulation) overlay network. This value is normally configured automatically.
`genevePort`	`integer`	The UDP port for the Geneve overlay network.

You can only change the configuration for your cluster network provider during cluster installation.

Example OVN-Kubernetes configuration

defaultNetwork:
  type: OVNKubernetes
  ovnKubernetesConfig:
    mtu: 1400
    genevePort: 6081

kubeProxyConfig object configuration

The values for the kubeProxyConfig object are defined in the following table:

Field Type Description

iptablesSyncPeriod

string

The refresh period for iptables rules. The default value is 30s. Valid suffixes include s, m, and h and are described in the Go time package documentation.

Because of performance improvements introduced in OKD 4.3 and greater, adjusting the iptablesSyncPeriod parameter is no longer necessary.

proxyArguments.iptables-min-sync-period

array

The minimum duration before refreshing iptables rules. This field ensures that the refresh does not happen too frequently. Valid suffixes include s, m, and h and are described in the Go time package. The default value is:

kubeProxyConfig:
  proxyArguments:
    iptables-min-sync-period:
    - 0s

Cluster Network Operator example configuration

A complete CNO configuration is specified in the following example:

Example Cluster Network Operator object

apiVersion: operator.openshift.io/v1
kind: Network
metadata:
  name: cluster
spec:
  clusterNetwork: (1)
  - cidr: 10.128.0.0/14
    hostPrefix: 23
  serviceNetwork: (1)
  - 172.30.0.0/16
  defaultNetwork: (1)
    type: OpenShiftSDN
    openshiftSDNConfig:
      mode: NetworkPolicy
      mtu: 1450
      vxlanPort: 4789
  kubeProxyConfig:
    iptablesSyncPeriod: 30s
    proxyArguments:
      iptables-min-sync-period:
      - 0s