When using quiz restriction by ip address, using range type 1: xxx.xxx.xxx.xxx/xx, on 64 bit CPU, result is unexpected. Add the '+' line :
+++ lib/moodlelib.php
@@ -7029,6 +7029,7 @@
if (strpos($subnet, '/') !== false)
else if (strpos($subnet, '-') !== false) {/// type 3
$subnetparts = explode('.', $subnet);