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Understanding the Cluster Network Operator (CNO) | Networking | OpenShift Container Platform 4.2
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Cluster Network Operator in OpenShift Container Platform

The Cluster Network Operator (CNO) deploys and manages the cluster network components on an OpenShift Container Platform cluster, including the default Container Network Interface (CNI) 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 a different SDN plug-in if selected during cluster installation, using a DaemonSet.

Procedure

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

  1. Run the following command to view the deployment status:

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

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

  2. Run the following command to view the state of the Cluster Network Operator:

    $ oc get clusteroperator/network

NAME      VERSION   AVAILABLE   PROGRESSING   DEGRADED   SINCE
network   4.2.0     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 OpenShift Container Platform 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

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 custom resource (CR)

The cluster network configuration in the Network.operator.openshift.io custom resource (CR) stores the configuration settings for the Cluster Network Operator (CNO). The Operator manages the cluster network.

You can specify the cluster network configuration for your OpenShift Container Platform cluster by setting the parameters for the defaultNetwork parameter in the CNO CR. The following CR displays the default configuration for the CNO and explains both the parameters you can configure and valid parameter values:

Cluster Network Operator CR
apiVersion: operator.openshift.io/v1
kind: Network
metadata:
  name: cluster
spec:
  clusterNetwork: (1)
  - cidr: 10.128.0.0/14
    hostPrefix: 23
  serviceNetwork: (2)
  - 172.30.0.0/16
  defaultNetwork: (3)
    ...
  kubeProxyConfig: (4)
    iptablesSyncPeriod: 30s (5)
    proxyArguments:
      iptables-min-sync-period: (6)
      - 30s
1 A list specifying the blocks of IP addresses from which Pod IPs are allocated and the subnet prefix length assigned to each individual node.
2 A block of IP addresses for services. The OpenShift SDN default Container Network Interface (CNI) network plug-in supports only a single IP address block for the service network.
3 Configures the software-defined networking (SDN) for the cluster network.
4 The parameters for this object specify the Kubernetes network proxy (kube-proxy) configuration.
5 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.
6 The minimum duration before refreshing iptables rules. This parameter ensures that the refresh does not happen too frequently. Valid suffixes include s, m, and h and are described in the Go time package

Configuration parameters for OpenShift SDN

The following YAML object describes the configuration parameters for OpenShift SDN default CNI network provider:

defaultNetwork:
  type: OpenShiftSDN (1)
  openshiftSDNConfig: (2)
    mode: NetworkPolicy (3)
    mtu: 1450 (4)
    vxlanPort: 4789 (5)
1 The default CNI network provider plug-in being used. OpenShift SDN is the only plug-in supported in OpenShift Container Platform 4.2.
2 OpenShift SDN specific configuration parameters.
3 The network isolation mode for the OpenShift SDN CNI plug-in.
4 MTU for the VXLAN overlay network. This value is normally configured automatically.
5 The port to use for all VXLAN packets. The default value is 4789.

Cluster Network Operator example CR

A complete CR for the CNO is displayed in the following example:

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