Many entities have a status attribute called state, whose value
    reflects the current operational state of the entity. The value
    of state is usually either:

    off   The entity is disabled. In this state the entity exists and
          can be manipulated in various ways (for example, by having
          its characteristics modified), but will not perform its
          primary functions.

    on    The entity is enabled. In this state the entity is fully
          operational.

    Use the disable command to place the entity in its disabled
    (off) state. Many entities do not permit you to modify their
    characteristics while they are enabled, so you must use the
    disable command before using the add, remove, or set commands.
    Also, it is often the case that you cannot delete an entity while
    it is enabled, so you must use the disable command before using
    the delete command. For example,

    ncl> disable modem connect line line-1

    disables the entity to suspend its operation temporarily and
    suspends operation of the corresponding physical line.