// Module included in the following assemblies:
//
// * networking/multiple_networks/secondary_networks/creating-secondary-nwt-other-cni.adoc

//37.1. VLAN overview
//
:_mod-docs-content-type: REFERENCE
[id="nw-multus-vlan-object_{context}"]
= Configuration for a VLAN secondary network

[role="_abstract"]  
The VLAN CNI plugin JSON configuration object describes the configuration parameters for the VLAN, `vlan`, CNI plugin. The following table details these parameters:

[cols=".^2,.^2,.^6",options="header"]
|====
|Field|Type|Description

|`cniVersion`
|`string`
|The CNI specification version. The `0.3.1` value is required.

|`name`
|`string`
|The mandatory, unique identifier assigned to this CNI network attachment definition. It is used by the container runtime to select the correct network configuration and serves as the key for persistent resource state management, such as IP address allocations.

|`type`
|`string`
|The name of the CNI plugin to configure: `vlan`.

|`master`
|`string`
|The Ethernet interface to associate with the network attachment. If a `master` is not specified, the interface for the default network route is used.

|`vlanId`
|`integer`
|Set the ID of the `vlan`.

|`ipam`
|`object`
|The configuration object for the IPAM CNI plugin. The plugin manages IP address assignment for the attachment definition.

|`mtu`
|`integer`
|Optional: Set the maximum transmission unit (MTU) to the specified value. The default value is automatically set by the kernel.

|`dns`
|`integer`
|Optional: DNS information to return. For example, a priority-ordered list of DNS nameservers.

|`linkInContainer`
|`boolean`
|Optional: Specifies whether the `master` interface is in the container network namespace or the main network namespace. Set the value to `true` to request the use of a container namespace `master` interface.

|====

[IMPORTANT]
====
A `NetworkAttachmentDefinition` custom resource definition (CRD) with a `vlan` configuration can be used only on a single pod in a node because the CNI plugin cannot create multiple `vlan` subinterfaces with the same `vlanId` on the same `master` interface.
====

[id="nw-multus-vlan-config-example_{context}"]
== VLAN configuration example

The following example demonstrates a `vlan` configuration with a secondary network that is named `vlan-net`:

[source,json]
----
{
  "name": "vlan-net",
  "cniVersion": "0.3.1",
  "type": "vlan",
  "master": "eth0",
  "mtu": 1500,
  "vlanId": 5,
  "linkInContainer": false,
  "ipam": {
      "type": "host-local",
      "subnet": "10.1.1.0/24"
  },
  "dns": {
      "nameservers": [ "10.1.1.1", "8.8.8.8" ]
  }
}
----

* `ipam.type.host-local`: Allocates IPv4 and IPv6 IP addresses from a specified set of address ranges. IPAM plugin stores the IP addresses locally on the host filesystem so that the addresses remain unique to the host.