As a cluster administrator, you can configure an additional network for your cluster using the macvlan Container Network Interface (CNI) plug-in with advanced customization. When a Pod is attached to the network, the plug-in creates a sub-interface from the parent interface on the host. A unique hardware mac address is generated for each sub-device.

The unique MAC addresses this plug-in generates for sub-interfaces might not be compatible with the security polices of your cloud provider.

You specify a configuration with a CNI object. This approach allows you to specify additional configuration options that are not available when using a YAML configuration.

Creating an additional network attachment with the macvlan CNI 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 CLI (oc).

  • Log in as a user with cluster-admin privileges.

Procedure

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

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

    $ oc edit networks.operator.openshift.io cluster
  2. Modify the CR that you are creating by adding the configuration for the additional network you are creating, as in the following example CR.

    The following YAML configures the macvlan CNI plug-in:

    apiVersion: operator.openshift.io/v1
    kind: Network
    metadata:
      name: cluster
    spec:
      additionalNetworks: (1)
      - name: test-network-1
        namespace: test-1
        type: Raw
        rawCNIConfig: '{
          "cniVersion": "0.3.1",
          "name": "test-network-1",
          "type": "macvlan",
          "master": "eth1",
          "ipam": {
            "type": "static",
            "addresses": [
              {
                "address": "191.168.1.23"
              }
            ]
          }
        }'
    1 Specify the configuration for the additional network attachment definition.
  3. Save your changes and quit the text editor to commit your changes.

  4. 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
    test-network-1       14m

Configuration for macvlan CNI plug-in

The configuration for an additional network attachment that uses the macvlan Container Network Interface (CNI) plug-in is provided in two parts:

  • Cluster Network Operator (CNO) configuration

  • CNI plug-in configuration

The CNO configuration specifies the name for the additional network attachment and the namespace to create the attachment in. The plug-in is configured by a JSON object specified by the rawCNIConfig parameter in the CNO configuration.

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 plug-in configuration in JSON format, which is based on the following template.

The following object describes the configuration parameters for the macvlan CNI plug-in:

macvlan CNI plug-in JSON configuration object
{
  "cniVersion": "0.3.1",
  "name": "<name>", (1)
  "type": "macvlan",
  "mode": "<mode>", (2)
  "master": "<master>", (3)
  "mtu": <mtu>, (4)
  "ipam": { (5)
    ...
  }
}
1 Specify a name for the additional network attachment that you are creating. The name must be unique within the specified namespace.
2 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.
3 The ethernet interface to associate with the virtual interface. If a value is not specified, then the host system’s primary ethernet interface is used.
4 Set the maximum transmission unit (MTU) to the specified value. The default value is automatically set by the kernel.
5 Specify a configuration object for the ipam CNI plug-in. The plug-in manages IP address assignment for the attachment definition.

macvlan configuration example

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

name: macvlan-net
namespace: work-network
type: Raw
rawCNIConfig: |-
  {
    "cniVersion": "0.3.1",
    "name": "macvlan-net",
    "type": "macvlan",
    "master": "eth1",
    "mode": "bridge",
    "ipam": {
      "type": "dhcp"
      }
  }

Configuration for ipam CNI plug-in

The ipam Container Network Interface (CNI) plug-in provides IP address management (IPAM) for other CNI plug-ins.

You can use the following methods for IP address assignment:

  • 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 plug-in.

Static IP address assignment configuration

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

Static assignment configuration
{
  "ipam": {
    "type": "static",
    "addresses": [ (1)
      {
        "address": "<address>", (2)
        "gateway": "<gateway>" (3)
      }
    ],
    "routes": [ (4)
      {
        "dst": "<dst>" (5)
        "gw": "<gw>" (6)
      }
    ],
    "dns": { (7)
      "nameservers": ["<nameserver>"], (8)
      "domain": "<domain>", (9)
      "search": ["<search_domain>"] (10)
    }
  }
}
1 An array describing IP addresses to assign to the virtual interface. Both IPv4 and IPv6 IP addresses are supported.
2 An IP address that you specify.
3 The default gateway to route egress network traffic to.
4 An array describing routes to configure inside the Pod.
5 The IP address range in CIDR format.
6 The gateway where network traffic is routed.
7 Optional: DNS configuration.
8 An of array of one or more IP addresses for to send DNS queries to.
9 The default domain to append to a host name. For example, if the domain is set to example.com, a DNS lookup query for example-host is rewritten as example-host.example.com.
10 An array of domain names to append to an unqualified host name, such as example-host, during a DNS lookup query.

Dynamic IP address 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
    rawCNIConfig: |-
    {
      "name": "dhcp-shim",
      "cniVersion": "0.3.1",
      "type": "bridge",
      "ipam": {
        "type": "dhcp"
      }
    }
DHCP assignment configuration
{
  "ipam": {
    "type": "dhcp"
  }
}

Dynamic IP address assignment configuration with Whereabouts

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

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

Whereabouts assignment configuration
{
  "ipam": {
    "type": "whereabouts",
    "range": "<range>", (1)
    "exclude": ["<exclude_part>, ..."], (2)
  }
}
1 Specify an IP address and range in CIDR notation. IP addresses are assigned from within this range of addresses.
2 Optional: Specify a list of IP addresses and ranges in CIDR notation. IP addresses within an excluded address range are not assigned.

Static IP address assignment configuration example

You can configure ipam for static IP address assignment:

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

Dynamic IP address assignment configuration example using DHCP

You can configure ipam for DHCP:

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

Dynamic IP address assignment configuration example using Whereabouts

You can configure ipam to use Whereabouts:

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