Morning_HS,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
</style>
<script>
window.addEventListener('DOMContentLoaded', function() {
var sel = document.querySelector('#ip_parameters'),
input = document.querySelectorAll('.auto');
sel.addEventListener('change', function() {
var disable = this.value == 'ip_auto';
[].forEach.call( input, function(el) {
disable ? el.setAttribute('disabled', 'disabled') :
el.removeAttribute('disabled')
});
});
});
</script>
</head>
<body>
<label for="ip_parameters">Настройка параметров IP:</label>
<select name="ip_parameters" id="ip_parameters" style="width: 250px;">
<option value="ip_auto">Автоматическая</option>
<option value="ip_hand" selected="selected">Вручную</option></select><br>
<label for="ip_address">IP-адрес:</label>
<input name="ip_address" type="text" class="auto"><br>
<label for="ip_mask">Маска подсети:</label>
<input name="ip_mask" type="text" class="auto"><br>
<label for="default_gate">Основной шлюз:</label>
<input name="ip_mask" type="text" class="auto"><br>
<label for="DNS_1">DNS_1:</label>
<input name="DNS_1" type="text" class="auto"><br>
<label for="DNS_2">DNS_2:</label>
<input name="DNS_2" type="text" class="auto"><br>
<label for="DNS_3">DNS_3:</label>
<input name="DNS_3" type="text" class="auto"><br>
</body>
</html>