diff --git a/NEXT.md b/NEXT.md
index f0ed0d8..ef33ab9 100644
--- a/NEXT.md
+++ b/NEXT.md
@@ -1,14 +1,10 @@
 # NEXT_STEPS
 
 ## Aktive Aufgaben (priorisiert)
-- [ ] [#11] Encoding- und Umlautfehler bereinigen (inkl. Anzeige in UI-Dateien und Markdown-Dokumenten)
 
 ## Verifikation (Status unklar, nicht als erledigt markieren ohne Reproduktion + Commit)
 - [ ] [#15] Neue Verbindung: Netzwerkdose auswählbar (Regressionstest in UI durchführen)
 
 ## gefundene bugs
-- [ ] device löschen geht nicht
 - [ ] TODO Design vereinheitlichen
 
-
-- [ ] Validierungsregeln fuer Topologie fest verdrahten (Patchpanel-Port nur mit Patchpanel-Port oder Netzwerkbuchsen-Port).
diff --git a/app/api/connections.php b/app/api/connections.php
index d05631b..d2c2ff5 100644
--- a/app/api/connections.php
+++ b/app/api/connections.php
@@ -77,6 +77,19 @@ function endpointExists($sql, string $type, int $id): bool
     return false;
 }
 
+function isTopologyPairAllowed(string $typeA, string $typeB): bool
+{
+    $allowed = ['device' => true, 'module' => true, 'outlet' => true, 'patchpanel' => true];
+    if (!isset($allowed[$typeA]) || !isset($allowed[$typeB])) {
+        return false;
+    }
+    if ($typeA === 'patchpanel' || $typeB === 'patchpanel') {
+        return ($typeA === 'patchpanel' && in_array($typeB, ['patchpanel', 'outlet'], true))
+            || ($typeB === 'patchpanel' && in_array($typeA, ['patchpanel', 'outlet'], true));
+    }
+    return true;
+}
+
 function loadConnections($sql): void
 {
     $contextType = strtolower(trim((string)($_GET['context_type'] ?? 'all')));
@@ -189,6 +202,9 @@ function saveConnection($sql): void
     if ($portAId <= 0 || $portBId <= 0) {
         jsonError('port_a_id und port_b_id sind erforderlich', 400);
     }
+    if (!isTopologyPairAllowed($portAType, $portBType)) {
+        jsonError('Patchpanel-Ports duerfen nur mit Patchpanel-Ports oder Netzwerkdosen-Ports verbunden werden', 400);
+    }
 
     if ($portAType === $portBType && $portAId === $portBId) {
         jsonError('Port A und Port B duerfen nicht identisch sein', 400);
diff --git a/app/assets/js/connections-edit-form.js b/app/assets/js/connections-edit-form.js
index 49ab786..6c656e8 100644
--- a/app/assets/js/connections-edit-form.js
+++ b/app/assets/js/connections-edit-form.js
@@ -51,8 +51,49 @@
         });
     }
 
+    function enforceTopologyTypeRules(typeA, typeB) {
+        const allowWithPatchpanel = { patchpanel: true, outlet: true };
+        const selectedA = typeA.value;
+        const selectedB = typeB.value;
+
+        const applyRules = (sourceType, targetSelect) => {
+            for (const option of targetSelect.options) {
+                const value = option.value;
+                if (!value) {
+                    option.disabled = false;
+                    continue;
+                }
+                if (sourceType === 'patchpanel') {
+                    option.disabled = !allowWithPatchpanel[value];
+                } else {
+                    option.disabled = false;
+                }
+            }
+            if (targetSelect.selectedOptions.length > 0 && targetSelect.selectedOptions[0].disabled) {
+                targetSelect.value = '';
+            }
+        };
+
+        applyRules(selectedA, typeB);
+        applyRules(selectedB, typeA);
+    }
+
     document.addEventListener('DOMContentLoaded', () => {
         bindPair('port_a_type', 'port_a_id');
         bindPair('port_b_type', 'port_b_id');
+
+        const typeA = document.getElementById('port_a_type');
+        const typeB = document.getElementById('port_b_type');
+        if (!typeA || !typeB) {
+            return;
+        }
+
+        const syncRules = () => {
+            enforceTopologyTypeRules(typeA, typeB);
+        };
+
+        syncRules();
+        typeA.addEventListener('change', syncRules);
+        typeB.addEventListener('change', syncRules);
     });
 })();
diff --git a/app/modules/connections/save.php b/app/modules/connections/save.php
index 8f0a51d..cd001c4 100644
--- a/app/modules/connections/save.php
+++ b/app/modules/connections/save.php
@@ -42,6 +42,18 @@ $normalizePortType = static function (string $value): string {
 $portAType = $normalizePortType((string)$portAType);
 $portBType = $normalizePortType((string)$portBType);
 
+$isTopologyPairAllowed = static function (string $typeA, string $typeB): bool {
+    $allowed = ['device' => true, 'module' => true, 'outlet' => true, 'patchpanel' => true];
+    if (!isset($allowed[$typeA]) || !isset($allowed[$typeB])) {
+        return false;
+    }
+    if ($typeA === 'patchpanel' || $typeB === 'patchpanel') {
+        return ($typeA === 'patchpanel' && in_array($typeB, ['patchpanel', 'outlet'], true))
+            || ($typeB === 'patchpanel' && in_array($typeA, ['patchpanel', 'outlet'], true));
+    }
+    return true;
+};
+
 // =========================
 // Validierung (einfach)
 // =========================
@@ -50,6 +62,9 @@ $errors = [];
 if ($portAId <= 0 || $portBId <= 0) {
     $errors[] = "Beide Ports sind erforderlich";
 }
+if (!$isTopologyPairAllowed($portAType, $portBType)) {
+    $errors[] = "Patchpanel-Ports duerfen nur mit Patchpanel-Ports oder Netzwerkdosen-Ports verbunden werden";
+}
 
 $otherConnections = $sql->get(
     "SELECT id, port_a_type, port_a_id, port_b_type, port_b_id
diff --git a/app/modules/devices/delete.php b/app/modules/devices/delete.php
index a4e66da..06fc9ed 100644
--- a/app/modules/devices/delete.php
+++ b/app/modules/devices/delete.php
@@ -56,10 +56,10 @@ $dependencies = $sql->single(
         (
             SELECT COUNT(*)
             FROM connections c
-            WHERE (c.port_a_type = 'device' AND c.port_a_id IN (
+            WHERE ((c.port_a_type = 'device' OR c.port_a_type = 'device_ports') AND c.port_a_id IN (
                     SELECT dp3.id FROM device_ports dp3 WHERE dp3.device_id = ?
                   ))
-               OR (c.port_b_type = 'device' AND c.port_b_id IN (
+               OR ((c.port_b_type = 'device' OR c.port_b_type = 'device_ports') AND c.port_b_id IN (
                     SELECT dp4.id FROM device_ports dp4 WHERE dp4.device_id = ?
                   ))
         ) AS connection_count",
@@ -108,8 +108,8 @@ if ($hasDependencies && !$forceDelete) {
 // Connections referenzieren device_ports nur logisch, daher manuell entfernen.
 $sql->set(
     "DELETE FROM connections
-     WHERE (port_a_type = 'device' AND port_a_id IN (SELECT id FROM device_ports WHERE device_id = ?))
-        OR (port_b_type = 'device' AND port_b_id IN (SELECT id FROM device_ports WHERE device_id = ?))",
+     WHERE ((port_a_type = 'device' OR port_a_type = 'device_ports') AND port_a_id IN (SELECT id FROM device_ports WHERE device_id = ?))
+        OR ((port_b_type = 'device' OR port_b_type = 'device_ports') AND port_b_id IN (SELECT id FROM device_ports WHERE device_id = ?))",
     "ii",
     [$deviceId, $deviceId]
 );
diff --git a/app/modules/devices/edit.php b/app/modules/devices/edit.php
index 72d87cf..5fd3cbd 100644
--- a/app/modules/devices/edit.php
+++ b/app/modules/devices/edit.php
@@ -47,10 +47,10 @@ if ($isEdit) {
             (
                 SELECT COUNT(*)
                 FROM connections c
-                WHERE (c.port_a_type = 'device' AND c.port_a_id IN (
+                WHERE ((c.port_a_type = 'device' OR c.port_a_type = 'device_ports') AND c.port_a_id IN (
                         SELECT dp3.id FROM device_ports dp3 WHERE dp3.device_id = ?
                       ))
-                   OR (c.port_b_type = 'device' AND c.port_b_id IN (
+                   OR ((c.port_b_type = 'device' OR c.port_b_type = 'device_ports') AND c.port_b_id IN (
                         SELECT dp4.id FROM device_ports dp4 WHERE dp4.device_id = ?
                       ))
             ) AS connection_count",
diff --git a/app/modules/devices/list.php b/app/modules/devices/list.php
index c41a448..eb02118 100644
--- a/app/modules/devices/list.php
+++ b/app/modules/devices/list.php
@@ -97,10 +97,10 @@ $devices = $sql->get(
         (
             SELECT COUNT(*)
             FROM connections c
-            WHERE (c.port_a_type = 'device' AND c.port_a_id IN (
+            WHERE ((c.port_a_type = 'device' OR c.port_a_type = 'device_ports') AND c.port_a_id IN (
                     SELECT dp3.id FROM device_ports dp3 WHERE dp3.device_id = d.id
                   ))
-               OR (c.port_b_type = 'device' AND c.port_b_id IN (
+               OR ((c.port_b_type = 'device' OR c.port_b_type = 'device_ports') AND c.port_b_id IN (
                     SELECT dp4.id FROM device_ports dp4 WHERE dp4.device_id = d.id
                   ))
         ) AS connection_count