YANG Basics

It’s not really necessary to understand how YANG works to write a profile but you need some basic understanding.

Basic Types

• container - A container is just a placeholder, sort of like a map or dictionary. A container doesn’t store any information per se, instead, it contains attributes of any type. For example, the following config object would be a valid container with three attributes of various types:

  container config:
      leaf description: string
      leaf mtu: uint16
      leaf enabled: boolean
  

• leaf - A leaf is an attribute that stores information. Leafs are of a type and values have to be valid for the given type. For example:

  leaf descrpition: string # Any string is valid
  leaf mtu: uint16         # -1 is not valid but 1500 is
  leaf enabled: boolean    # true, false, 1, 0, True, False are valid
  

Note

There can be further restrictions, for example the leaf prefix-length is of type uint8 but it’s further restricted with the option range 0..32

• YANG lists - A YANG list represents a container in the tree that will represent individual members of a list. For example:

  container interfaces:
      list interface:
          container config:
              leaf description: string
              leaf mtu: uint16
              leaf enabled: boolean
  

As we start adding elements to the interface list, each individual interface will have it’s own attributes. For example:

interfaces:
    interface["eth1"]:
        config:
            description: "An interface"
            mtu: 1500
            enabled: true
    interface["eth2"]:
        config:
            description: "Another interface"
            mtu: 9000
            enabled: false