diff --git a/attendance.php b/attendance.php
index 8b9bda8..f702fbf 100644
--- a/attendance.php
+++ b/attendance.php
@@ -43,6 +43,13 @@ if (empty(get_config('attendance', 'studentscanmark')) || empty($attforsession->
     redirect(new moodle_url('/mod/attendance/view.php', array('id' => $cm->id)));
     exit;
 }
+
+// Check if subnet is set and if the user is in the allowed range.
+if (!empty($attendance->subnet) && !address_in_subnet(getremoteaddr(), $attendance->subnet)) {
+    notice(get_string('subnetwrong', 'attendance'));
+    exit; // Notice calls this anyway.
+}
+
 $pageparams->sessionid = $id;
 $att = new mod_attendance_structure($attendance, $cm, $course, $PAGE->context, $pageparams);
 
diff --git a/classes/structure.php b/classes/structure.php
index d4d591c..df7d823 100644
--- a/classes/structure.php
+++ b/classes/structure.php
@@ -59,6 +59,8 @@ class mod_attendance_structure {
     /** current page parameters */
     public $pageparams;
 
+    public $subnet;
+
     private $groupmode;
 
     private $statuses;
@@ -1063,4 +1065,4 @@ class mod_attendance_structure {
 
         return null;
     }
-}
+}
\ No newline at end of file
diff --git a/db/install.xml b/db/install.xml
index 5259382..0704227 100644
--- a/db/install.xml
+++ b/db/install.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8" ?>
-<XMLDB PATH="mod/attendance/db" VERSION="20160829" COMMENT="XMLDB file for Moodle mod/attendance"
+<XMLDB PATH="mod/attendance/db" VERSION="20161107" COMMENT="XMLDB file for Moodle mod/attendance"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="../../../lib/xmldb/xmldb.xsd"
         >
@@ -11,6 +11,7 @@
         <FIELD NAME="name" TYPE="char" LENGTH="255" NOTNULL="false" SEQUENCE="false"/>
         <FIELD NAME="grade" TYPE="int" LENGTH="10" NOTNULL="true" DEFAULT="100" SEQUENCE="false" COMMENT="This is maximum grade for instance"/>
         <FIELD NAME="timemodified" TYPE="int" LENGTH="10" NOTNULL="true" DEFAULT="0" SEQUENCE="false" COMMENT="The time the settings for this attendance instance were last modified."/>
+        <FIELD NAME="subnet" TYPE="char" LENGTH="255" NOTNULL="false" SEQUENCE="false" COMMENT="Restrict ability for students to mark by subnet."/>
       </FIELDS>
       <KEYS>
         <KEY NAME="primary" TYPE="primary" FIELDS="id" COMMENT="Primary key for attendance"/>
@@ -103,4 +104,4 @@
       </INDEXES>
     </TABLE>
   </TABLES>
-</XMLDB>
\ No newline at end of file
+</XMLDB>
diff --git a/db/upgrade.php b/db/upgrade.php
index 4f32399..ce819a3 100644
--- a/db/upgrade.php
+++ b/db/upgrade.php
@@ -192,6 +192,14 @@ function xmldb_attendance_upgrade($oldversion=0) {
         // Attendance savepoint reached.
         upgrade_mod_savepoint(true, 2016082900, 'attendance');
     }
+    if ($oldversion < 2016112100) {
+        $table = new xmldb_table('attendance');
+        $newfield = $table->add_field('subnet', XMLDB_TYPE_CHAR, '255', null, null, null, null, 'timemodified');
+        if (!$dbman->field_exists($table, $newfield)) {
+            $dbman->add_field($table, $newfield);
+        }
+        upgrade_mod_savepoint(true, 2016112100, 'attendance');
+    }
 
     return $result;
-}
+}
\ No newline at end of file
diff --git a/lang/en/attendance.php b/lang/en/attendance.php
index 6e04022..d0dc440 100644
--- a/lang/en/attendance.php
+++ b/lang/en/attendance.php
@@ -332,4 +332,7 @@ $string['repeatuntil'] = 'Repeat until';
 $string['repeaton'] = 'Repeat on';
 $string['invalidsessionendtime'] = 'The end time must be greater than start time';
 $string['deletedgroup'] = 'The group associated with this session has been deleted';
-$string['search:activity'] = 'Attendance - activity information';
\ No newline at end of file
+$string['extrarestrictions'] = 'Extra restrictions';
+$string['requiresubnet'] = 'Students can only record own attendance from these computers.';
+$string['subnetwrong'] = 'Attendance can only be recorded from certain locations, and this computer is not on the allowed list.';
+$string['requiresubnet_help'] = 'Attendance recording may be restricted to particular subnets by specifying a comma-separated list of partial or full IP addresses.';
\ No newline at end of file
diff --git a/mod_form.php b/mod_form.php
index 133bc87..7ad84d0 100644
--- a/mod_form.php
+++ b/mod_form.php
@@ -39,6 +39,10 @@ class mod_attendance_mod_form extends moodleform_mod {
      * @return void
      */
     public function definition() {
+        $attendanceconfig = get_config('attendance');
+        if (!isset($attendanceconfig->subnet)) {
+            $attendanceconfig->subnet = '';
+        }
         $mform    =& $this->_form;
 
         $mform->addElement('header', 'general', get_string('general', 'form'));
@@ -52,6 +56,14 @@ class mod_attendance_mod_form extends moodleform_mod {
         $this->standard_grading_coursemodule_elements();
 
         $this->standard_coursemodule_elements(true);
+
+        $mform->addElement('header', 'security', get_string('extrarestrictions', 'attendance'));
+        // IP address.
+        $mform->addElement('text', 'subnet', get_string('requiresubnet', 'attendance'), array('size' => '164'));
+        $mform->setType('subnet', PARAM_TEXT);
+        $mform->addHelpButton('subnet', 'requiresubnet', 'attendance');
+        $mform->setDefault('subnet', $attendanceconfig->subnet);
+
         $this->add_action_buttons();
     }
-}
+}
\ No newline at end of file
diff --git a/version.php b/version.php
index c726334..7a0efad 100644
--- a/version.php
+++ b/version.php
@@ -23,9 +23,9 @@
  */
 defined('MOODLE_INTERNAL') || die();
 
-$plugin->version  = 2016082900;
+$plugin->version  = 2016112100;
 $plugin->requires = 2016052300;
 $plugin->release = '3.1.1.1';
 $plugin->maturity  = MATURITY_STABLE;
 $plugin->cron     = 0;
-$plugin->component = 'mod_attendance';
+$plugin->component = 'mod_attendance';
\ No newline at end of file