diff --git a/includes/common.php b/includes/common.php
index 04c681aaf..8b59ba774 100644
--- a/includes/common.php
+++ b/includes/common.php
@@ -1249,7 +1249,7 @@ function get_port_id ($ports_mapped, $port, $port_association_mode) {
     */
     $maps  = $ports_mapped['maps'];
 
-    if (in_array ($port_association_mode, array ('ifIndex', 'ifName', 'ifDescr'))) {
+    if (in_array ($port_association_mode, array ('ifIndex', 'ifName', 'ifDescr', 'ifAlias'))) {
         $port_id = $maps[$port_association_mode][$port[$port_association_mode]];
     }
 
diff --git a/includes/defaults.inc.php b/includes/defaults.inc.php
index 8dfa46c8d..bed0b577d 100644
--- a/includes/defaults.inc.php
+++ b/includes/defaults.inc.php
@@ -858,3 +858,6 @@ $config['update_channel']                               = 'master';
 
 // Default port association mode
 $config['default_port_association_mode'] = 'ifIndex';
+// Ignore ports which can't be mapped using a devices port_association_mode
+// See include/polling/ports.inc.php for a lenghty explanation.
+$config['ignore_unmapable_port'] = False;
diff --git a/includes/polling/port-adsl.inc.php b/includes/polling/port-adsl.inc.php
index e3567e26b..42b986428 100644
--- a/includes/polling/port-adsl.inc.php
+++ b/includes/polling/port-adsl.inc.php
@@ -39,10 +39,7 @@
 // adslAturPerfESs.1 = 0 seconds
 // adslAturPerfValidIntervals.1 = 0
 // adslAturPerfInvalidIntervals.1 = 0
-if (isset($port_stats[$port_id]['adslLineCoding'])) {
-    // Check to make sure Port data is cached.
-    $this_port = &$port_stats[$port_id];
-
+if (isset($this_port['adslLineCoding'])) {
     $rrdfile = get_port_rrdfile_path ($device['hostname'], $port_id, 'adsl');
 
     $rrd_create  = ' --step 300';
diff --git a/includes/polling/port-etherlike.inc.php b/includes/polling/port-etherlike.inc.php
index bf947b92d..729990162 100644
--- a/includes/polling/port-etherlike.inc.php
+++ b/includes/polling/port-etherlike.inc.php
@@ -1,11 +1,6 @@
 <?php
 
-if ($port_stats[$port_id] &&
-    $port['ifType'] == 'ethernetCsmacd' &&
-    isset($port_stats[$port_id]['dot3StatsIndex'])) {
-    // Check to make sure Port data is cached.
-    $this_port = &$port_stats[$port_id];
-
+if ($this_port['dot3StatsIndex'] and $port['ifType'] == 'ethernetCsmacd') {
     // TODO: remove legacy check?
     $old_rrdfile = $config['rrd_dir'].'/'.$device['hostname'].'/'.safename('etherlike-'.$port['ifIndex'].'.rrd');
     $rrd_file    = get_port_rrdfile_path ($device['hostname'], $port_id, 'dot3');
diff --git a/includes/polling/port-poe.inc.php b/includes/polling/port-poe.inc.php
index 7b598a6b8..f9fdc99db 100644
--- a/includes/polling/port-poe.inc.php
+++ b/includes/polling/port-poe.inc.php
@@ -35,12 +35,7 @@ $peth_oids = array(
     'pethMainPseConsumptionPower',
 );
 
-if ($port_stats[$port_id]
-    && $port['ifType'] == 'ethernetCsmacd'
-    && isset($port_stats[$port_id]['dot3StatsIndex'])) {
-    // Check to make sure Port data is cached.
-    $this_port = &$port_stats[$port_id];
-
+if ($this_port['dot3StatsIndex'] && $port['ifType'] == 'ethernetCsmacd') {
     $rrdfile = get_port_rrdfile_path ($device['hostname'], $port_id, 'poe');
     if (!file_exists($rrdfile)) {
         $rrd_create .= $config['rrd_rra'];
diff --git a/includes/polling/ports.inc.php b/includes/polling/ports.inc.php
index aabad8a2a..8f7767338 100644
--- a/includes/polling/ports.inc.php
+++ b/includes/polling/ports.inc.php
@@ -224,6 +224,7 @@ foreach ($ports_mapped['maps']['ifIndex'] as $ifIndex => $port_id) {
 }
 
 
+$ports_found = array ();
 // New interface detection
 foreach ($port_stats as $ifIndex => $port) {
     // Store ifIndex in port entry and prefetch ifName as we'll need it multiple times
@@ -238,6 +239,31 @@ foreach ($port_stats as $ifIndex => $port) {
 
         // Port newly discovered?
         if (! $ports[$port_id]) {
+            /**
+              * When using the ifName or ifDescr as means to map discovered ports to
+              * known ports in the DB (think of port association mode) it's possible
+              * that we're facing the problem that the ifName or ifDescr polled from
+              * the device is unset or an empty string (like when querying some ubnt
+              * devices...). If this happends we have no way to map this port to any
+              * port found in the database. As reported this situation may occur for
+              * the time of one poll and might resolve automagically before the next
+              * poller run happens. Without this special case this would lead to new
+              * ports added to the database each time this situation occurs. To give
+              * the user the choice between »a lot of new ports« and »some poll runs
+              * are missed but ports stay stable« the 'ignore_unmapable_port' option
+              * has been added to configure this behaviour. To skip the port in this
+              * loop is sufficient as the next loop is looping only over ports found
+              * in the database and "maps back". As we did not add a new port to the
+              * DB here, there's no port to be mapped to.
+              *
+              * I'm using the in_array() check here, as I'm not sure if an "ifIndex"
+              * can be legally set to 0, which would yield True when checking if the
+              * value is empty().
+              */
+            if ($config['ignore_unmapable_port'] === True and in_array ($port[$port_association_mode], array ('', Null))) {
+                continue;
+            }
+
             $port_id         = dbInsert(array('device_id' => $device['device_id'], 'ifIndex' => $ifIndex, 'ifName' => $ifName), 'ports');
             dbInsert(array('port_id' => $port_id), 'ports_statistics');
             $ports[$port_id] = dbFetchRow('SELECT * FROM `ports` WHERE `port_id` = ?', array($port_id));
@@ -255,9 +281,18 @@ foreach ($port_stats as $ifIndex => $port) {
             dbInsert(array('port_id' => $port_id), 'ports_statistics');
         }
 
-        // Assure stable mapping
-        $port_stats[$ifIndex]['port_id'] = $port_id;
+        /** Assure stable bidirectional port mapping between DB and polled data
+          *
+          * Store the *current* ifIndex in the port info array containing all port information
+          * fetched from the database, as this is the only means we have to map ports_stats we
+          * just polled from the device to a port in $ports. All code below an includeed below
+          * will and has to map a port using it's ifIndex.
+          */
         $ports[$port_id]['ifIndex'] = $ifIndex;
+        $port_stats[$ifIndex]['port_id'] = $port_id;
+
+	/* Build a list of all ports, identified by their port_id, found within this poller run. */
+	$ports_found[] = $port_id;
     }
 
     // Port vanished (mark as deleted)
@@ -274,11 +309,32 @@ echo "\n";
 // Loop ports in the DB and update where necessary
 foreach ($ports as $port) {
     $port_id = $port['port_id'];
+    $ifIndex = $port['ifIndex'];
 
-    echo 'Port ' . $port['ifName'] . ': ' . $port['ifDescr'] . '(' . $port['ifIndex'] . ') ';
-    if ($port_stats[$port['ifIndex']] && $port['disabled'] != '1') {
+    $port_info_string = 'Port ' . $port['ifName'] . ': ' . $port['ifDescr'] . " ($ifIndex / #$port_id) ";
+
+    /* We don't care for disabled ports, go on */
+    if ($port['disabled'] == 1) {
+        echo "$port_info_string disabled.\n";
+        continue;
+    }
+
+    /**
+     * If this port did not show up in $port_stats before it has been deleted
+     * since the last poller run. Mark it deleted in the database and go on.
+     */
+    if (! in_array ($port_id, $ports_found)) {
+        if ($port['deleted'] != '1') {
+            dbUpdate(array('deleted' => '1'), 'ports', '`device_id` = ? AND `port_id` = ?', array($device['device_id'], $port_id));
+            echo "$port_info_string deleted.\n";
+        }
+        continue;
+    }
+
+    echo $port_info_string;
+    if ($port_stats[$ifIndex]) {
         // Check to make sure Port data is cached.
-        $this_port = &$port_stats[$port['ifIndex']];
+        $this_port = &$port_stats[$ifIndex];
 
         if ($device['os'] == 'vmware' && preg_match('/Device ([a-z0-9]+) at .*/', $this_port['ifDescr'], $matches)) {
             $this_port['ifDescr'] = $matches[1];
@@ -625,19 +681,8 @@ foreach ($ports as $port) {
             $updated += dbUpdate($port['update_extended'], 'ports_statistics', '`port_id` = ?', array($port_id));
             d_echo("$updated updated");
         }
-
         // End Update Database
     }
-    else if ($port['disabled'] != '1') {
-        echo 'Port Deleted';
-        // Port missing from SNMP cache.
-        if ($port['deleted'] != '1') {
-            dbUpdate(array('deleted' => '1'), 'ports', '`device_id` = ? AND `port_id` = ?', array($device['device_id'], $port_id));
-        }
-    }
-    else {
-        echo 'Port Disabled.';
-    }//end if
 
     echo "\n";
 
@@ -647,3 +692,4 @@ foreach ($ports as $port) {
 
 // Clear Variables Here
 unset($port_stats);
+unset($ports_found);
diff --git a/sql-schema/100.sql b/sql-schema/100.sql
new file mode 100644
index 000000000..646e4c4e1
--- /dev/null
+++ b/sql-schema/100.sql
@@ -0,0 +1 @@
+INSERT INTO port_association_mode (name) values ('ifAlias');