librenms-librenms/includes/polling/os/nos.inc.php

<?php

$version      = trim(snmp_get($device, "1.3.6.1.4.1.1588.2.1.1.1.1.6.0", "-Ovq"), '"');
$hardware     = trim(snmp_get($device, "ENTITY-MIB::entPhysicalDescr.1", "-Ovq"), '"');
$serial       = trim(snmp_get($device, "1.3.6.1.2.1.47.1.1.1.1.11.1", "-Ovq"), '"');