def METHOD_NAME(self, ifacename, cmd_prefix=None):
    if os.path.exists('/sbin/dhclient3'):
        cmd = ['/sbin/dhclient3', '-x', '-pf',
               '/run/dhclient.%s.pid' %ifacename, '-lf',
               '/var/lib/dhcp3/dhclient.%s.leases' %ifacename,
               '%s' %ifacename]
    else:
        cmd = ['/sbin/dhclient', '-x', '-pf',
               '/run/dhclient.%s.pid' %ifacename,
               '-lf', '/var/lib/dhcp/dhclient.%s.leases' %ifacename,
               '%s' %ifacename]
    self._run_dhclient_cmd(cmd, cmd_prefix)