librenms-librenms/includes/discovery/sensors/fanspeed/xos.inc.php

<?php

echo(" EXTREME-BASE-MIB ");

// Fan Speed
$oid = ".1.3.6.1.4.1.1916.1.1.1.9.1.4";
$oids = snmpwalk_cache_multi_oid($device, $oid, [], "EXTREME-BASE-MIB");

foreach ($oids as $index => $entry) {
    // fix index to a proper int
    preg_match('/^.*\.([^\.]*)$/', "$index", $matches);
    $index = $matches[1];
    // substract 100 from index to start from 1 instead of 101
    $modindex = ($index - 100);
    $oid = ".1.3.6.1.4.1.1916.1.1.1.9.1.4.$index";
    $value = snmp_get($device, $oid, '-Oqv', 'EXTREME-BASE-MIB');
    $descr = "Fan Speed $modindex";
    // round function used to round limit values to hundreds to avoid h/w/l limits being changed on every discovery as a change of 1rpm for fan speed would cause the limit values to change since they're dynamically calculated
    $high_limit      = round_Nth(($value * 1.5), 100);
    $high_warn_limit = round_Nth(($value * 1.25), 100);
    $low_warn_limit  = round_Nth(($value * 0.75), 100);
    $low_limit       = round_Nth(($value * 0.5), 100);
    if (is_numeric($value)) {
        discover_sensor($valid['sensor'], 'fanspeed', $device, $oid, $index, 'extreme-fanspeed', $descr, '1', '1', $low_limit, $low_warn_limit, $high_warn_limit, $high_limit, $value);
    }
}