The **ifconfig up** command is used to bring up an interface with the
specified configuration.

@static
@category ifconfig
@param {object} options The interface configuration.
@param {function} callback The callback function.
@returns {process} The child process.
@example

var options = {
interface: 'wlan0',
ipv4_address: '192.168.10.1',
ipv4_broadcast: '192.168.10.255',
ipv4_subnet_mask: '255.255.255.0'
};

ifconfig.up(options, function(err) {
// the interface is up
});
function up(options, callback) {
  return this.exec('ifconfig ' + options.interface +
    ' ' + options.ipv4_address +
    ' netmask ' + options.ipv4_subnet_mask +
    ' broadcast ' + options.ipv4_broadcast +
    ' up', callback);
}