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) network plugin 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 OVN-Kubernetes network plugin, or the network provider plugin 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 plugin, 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 plugin 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 network plugins 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 network plugin 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 plugin, 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 Red Hat OpenShift Networking network plugin is selected during installation. This value cannot be changed after cluster installation.

OKD uses the OVN-Kubernetes network plugin by default.

openshiftSDNConfig

object

This object is only valid for the OpenShift SDN network plugin.

ovnKubernetesConfig

object

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

Configuration for the OpenShift SDN network plugin

The following table describes the configuration fields for the OpenShift SDN network plugin:

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 plugin during cluster installation.

Example OpenShift SDN configuration

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

Configuration for the OVN-Kubernetes network plugin

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

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.

ipsecConfig

object

If the field is present, IPsec is enabled for the cluster.

policyAuditConfig

object

Specify a configuration object for customizing network policy audit logging. If unset, the defaults audit log settings are used.

gatewayConfig

object

Optional: Specify a configuration object for customizing how egress traffic is sent to the node gateway.

While migrating egress traffic, you can expect some disruption to workloads and service traffic until the Cluster Network Operator (CNO) successfully rolls out the changes.

v4InternalSubnet

If your existing network infrastructure overlaps with the 100.64.0.0/16 IPv4 subnet, you can specify a different IP address range for internal use by OVN-Kubernetes. You must ensure that the IP address range does not overlap with any other subnet used by your OKD installation. The IP address range must be larger than the maximum number of nodes that can be added to the cluster.

For example, if the clusterNetwork.cidr is 10.128.0.0/14 and the clusterNetwork.hostPrefix is /23, then the maximum number of nodes is 2^(23-14)=128. An IP address is also required for the gateway, network, and broadcast addresses. Therefore the internal IP address range must be at least a /24.

This field cannot be changed after installation.

The default value is 100.64.0.0/16.

v6InternalSubnet

If your existing network infrastructure overlaps with the fd98::/48 IPv6 subnet, you can specify a different IP address range for internal use by OVN-Kubernetes. You must ensure that the IP address range does not overlap with any other subnet used by your OKD installation. The IP address range must be larger than the maximum number of nodes that can be added to the cluster.

This field cannot be changed after installation.

The default value is fd98::/48.

Table 5. `policyAuditConfig` object
Field	Type	Description
`rateLimit`	integer	The maximum number of messages to generate every second per node. The default value is `20` messages per second.
`maxFileSize`	integer	The maximum size for the audit log in bytes. The default value is `50000000` or 50 MB.
`destination`	string	One of the following additional audit log targets: `libc` The libc `syslog()` function of the journald process on the host. `udp:<host>:<port>` A syslog server. Replace `<host>:<port>` with the host and port of the syslog server. `unix:<file>` A Unix Domain Socket file specified by `<file>`. `null` Do not send the audit logs to any additional target.
`syslogFacility`	string	The syslog facility, such as `kern`, as defined by RFC5424. The default value is `local0`.

Table 6. `gatewayConfig` object
Field	Type	Description
`routingViaHost`	`boolean`	Set this field to `true` to send egress traffic from pods to the host networking stack. For highly-specialized installations and applications that rely on manually configured routes in the kernel routing table, you might want to route egress traffic to the host networking stack. By default, egress traffic is processed in OVN to exit the cluster and is not affected by specialized routes in the kernel routing table. The default value is `false`. This field has an interaction with the Open vSwitch hardware offloading feature. If you set this field to `true`, you do not receive the performance benefits of the offloading because egress traffic is processed by the host networking stack.

You can only change the configuration for your cluster network plugin during cluster installation, except for the gatewayConfig field that can be changed at runtime as a post-installation activity.

Example OVN-Kubernetes configuration with IPSec enabled

defaultNetwork:
  type: OVNKubernetes
  ovnKubernetesConfig:
    mtu: 1400
    genevePort: 6081
    ipsecConfig: {}

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