Configuration and State Data

YANG can model state data and configuration data based on the "config" statement. If a node is tagged with "config false", its subhierarchy is flagged as state data. If a node is tagged with "config true", its subhierarchy is flagged as configuration data. When state data is queried using NETCONF's <get> operation, parent containers, lists, and key leaf nodes are also reported, providing a specific context for the state data.

In the following example, two leaf nodes are defined for each interface, a configured interface status and an observed speed. The observed speed is not configurable, so it can be returned with NETCONF's <get> operations, but not with <get-config> operations.

container interfaces {

  list interface {
    key "name";
  
    leaf name {
      type string;
    }

    leaf status {
      type boolean;
      default "true";
    }

    leaf observed-speed  {
      type yang:gauge64;
      units "bits/second";
      config false;
    }
  }
}