Assigning a secondary network to a VRF

Assigning a secondary network to a VRF
- Creating an additional network attachment with the CNI VRF plug-in

CNI VRF plug-in 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 https://access.redhat.com/support/offerings/techpreview/.

As a cluster administrator, you can configure an additional network for your VRF domain by using the CNI VRF plug-in. The virtual network created by this plug-in is associated with a physical interface that you specify.

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

Creating an additional network attachment with the CNI VRF plug-in

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.

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

Prerequisites

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

Procedure

Create the CNO CR by running the following command:
```
$ oc edit networks.operator.openshift.io cluster
```

Extend the CR that you are creating by adding the rawCNIConfig configuration for the additional network, as in the example CR below. The following YAML configures the CNI VRF plug-in:

apiVersion: operator.openshift.io/v1
kind: Network
metadata:
  name: cluster
  spec:
  additionalNetworks:
  - name: test-network-1
    namespace: test-1
    type: Raw
    rawCNIConfig: '{
      "cniVersion": "0.3.1",
      "name": "macvlan-vrf",
      "plugins": [  (1)
      {
        "type": "macvlan",  (2)
        "master": "eth1",
        "ipam": {
            "type": "static",
            "addresses": [
            {
                "address": "191.168.1.23/24"
            }
            ]
        }
      },
      {
        "type": "vrf",
        "vrfname": "example-vrf-name",  (3)
        "table": 1001   (4)
      }]
    }'

1	`plugins` must be a list. The first item in the list must be 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	`table` is the routing table ID. Optional. By default, the `tableid` parameter is used. If it is not specified, the CNI assigns a free routing table ID to the VRF.

VRF will function correctly only when the resource is of type netdevice.

Save your changes and quit the text editor to commit your changes.
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. There might be a delay before the CNO creates the CR.
```
$ oc get network-attachment-definitions -n <namespace>
```
Example output
```
NAME                       AGE
additional-network-1       14m
```

Verifying that the additional VRF network attachment is successful

To verify that the VRF CNI is correctly configured and the additional network attachment is attached, do the following:

Create a network that uses the VRF CNI.
Assign the network to a pod.
Verify that the pod network attachment is connected to the VRF additional network. SSH into the pod and run the following command:
```
$ ip vrf show
```
Example output
```
Name              Table
-----------------------
red                 10
```

Confirm the VRF interface is master of the secondary interface:

$ ip link

Example output

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