Considerations for ports and interfaces

The words "port" and "interface" have meanings that are different from other network operating systems. In the ArubaOS-CX operating system:

A port is the logical representation of a port.
An interface is the hardware representation of a port.
When creating a VLAN or LAG interface in the CLI, you are creating ports in the REST API.

Most resources have a hierarchical relationship. You must create the parent before you can create the child. However, ports and interfaces do not have a parent that is clear from the resource hierarchy. Therefore, there are some things you do differently from other resources when creating and deleting ports and interfaces:

Hardware interfaces are included in the database automatically. Considerations for interfaces apply to user-created interfaces such as VLAN interfaces or LAG interfaces.
When you insert a transceiver in the physical port, the port is automatically created. Because the port already exists, executing a POST request to create a port after a transceiver is inserted does not work.
Before you create a VLAN or LAG interface, you must create the port the interface will be referenced by.
When you create a port, if you choose a VRF other than the default VRF, you must create that VRF before you create the port.
When you create a port, you must explicitly designate either a VRF or the bridge that refers to the port. The POST method JSON model for a port includes the field referenced_by to designate this relationship.

The following example creates a port resource for a VLAN interface:
```
POST "https://192.0.2.5/rest/v1/system/ports"
{
  "name": "vlan200",
  "admin": "up",
  "interfaces": [],
  "referenced_by": "/rest/v1/system/vrfs/default",
  "vlan_tag": "/rest/v1/system/bridge/vlans/200",
  "description": "referenced by /system/bridge/vrfs/default"
}
```

When you create a VLAN or LAG interface, you must explicitly designate the port that refers to this interface. The POST method JSON model includes the field referenced_by to designate this relationship.

The following example creates a VLAN interface:

POST "https://192.0.2.5/rest/v1/system/interfaces"
{
  "name": "vlan200",
  "referenced_by": "/rest/v1/system/ports/vlan200",
  "description": "referenced by /system/bridge/ports/vlan200",
  "type": "vlansubint",
  "user_config": {
    "admin": "up"
  }
}

Only the POST method JSON models for ports and interfaces include the referenced_by field. The referenced_by field is not included in the response body for GET requests, and is not supported by the PUT method.
The ports and interfaces resources do not support the DELETE method. After the port or interface is removed from all the resources that reference it, the port or interface is removed from the system automatically. This automatic removal is done through the same process that automatically removes resources that have no parent resource.

For example, to delete the VLAN interface created in the preceding example, "/rest/v1/system/interfaces/vlan200", you must delete the port from the list of ports in the referring VRF.
Hewlett Packard Enterprise recommends that you include referenced_by information in the description field when you create the port or interface. By including this information when the port or interface is created, you avoid having to query all possible referring resources (such as all VRFs) when you want to remove the port or interface.