def get_config_ipv4_commands(delta, interface, existing):
    """Returns list of commands to be configured on a Layer 3 interface

    Args:
        delta (set): params to be configured
        interface (string): full name of logical interface,
            i.e. vla10, loopback10, port-channel20
        existing (dict): object created in the module that is from
           get_ipv4_interface() module

    Returns:
      list: ordered list of commands to be configured on the
       switch to get interface into desired state

    Note:
        Specific for Ansible module(s).  Not to be called otherwise.

    """
    commands = []
    delta = dict(delta)

    # loop used in the situation that just an IP address or just a
    # mask is changing, not both.
    for each in ['ip_addr', 'mask']:
        if each not in delta.keys():
            delta[each] = existing[each]

    command = 'ip address {ip_addr}/{mask}'.format(**delta)
    commands.append(command)
    commands.insert(0, 'interface ' + interface)

    return commands