diff --git a/android/app/src/main/java/de/data_it_solution/netdiag/NetDiagScannerPlugin.kt b/android/app/src/main/java/de/data_it_solution/netdiag/NetDiagScannerPlugin.kt
index 272a6ab..8a75408 100644
--- a/android/app/src/main/java/de/data_it_solution/netdiag/NetDiagScannerPlugin.kt
+++ b/android/app/src/main/java/de/data_it_solution/netdiag/NetDiagScannerPlugin.kt
@@ -82,14 +82,18 @@ class NetDiagScannerPlugin : Plugin() {
     @PluginMethod
     fun ipScan(call: PluginCall) {
         val subnet = call.getString("subnet") ?: return call.reject("subnet fehlt")
-        val base = subnet.substringBeforeLast('.', "192.168.1")
+        val hosts = hostsInSubnet(subnet)
+        if (hosts.isEmpty()) {
+            return call.reject("Subnetz ungültig oder zu groß (max /16): $subnet")
+        }
         io.launch {
             try {
-                // Parallel-Ping über das gesamte /24
+                // Parallel-Ping über ALLE Host-Adressen des Subnetzes — CIDR-genau,
+                // also exakt der Bereich, den die Netzmaske aufspannt (/24, /23, /22 …).
                 val alive = withContext(Dispatchers.IO) {
-                    (1..254).map { host ->
+                    hosts.map { ipInt ->
                         async {
-                            val ip = "$base.$host"
+                            val ip = intToIpv4(ipInt)
                             if (InetAddress.getByName(ip).isReachable(350)) ip else null
                         }
                     }.awaitAll().filterNotNull()
@@ -112,6 +116,51 @@ class NetDiagScannerPlugin : Plugin() {
         }
     }
 
+    /**
+     * Alle Host-IPs (als Int) eines CIDR-Subnetzes.
+     * "192.168.1.0/24" -> .1 bis .254, "10.0.0.0/22" -> 1022 Hosts usw.
+     * Ohne Praefix wird /24 angenommen. Netz- und Broadcast-Adresse sind
+     * ausgenommen (ausser /31, /32). Leer bei ungueltig oder > /16.
+     */
+    private fun hostsInSubnet(cidr: String): List<Int> {
+        val parts = cidr.trim().split('/')
+        val ipInt = ipv4ToInt(parts[0].trim()) ?: return emptyList()
+        val prefix = if (parts.size > 1) (parts[1].trim().toIntOrNull() ?: 24) else 24
+        if (prefix < 0 || prefix > 32) return emptyList()
+        val mask = if (prefix == 0) 0 else (-1 shl (32 - prefix))
+        val network = ipInt and mask
+        val broadcast = network or mask.inv()
+        val out = ArrayList<Int>()
+        if (prefix >= 31) {
+            var i = network
+            while (true) { out.add(i); if (i == broadcast) break; i++ }
+            return out
+        }
+        val count = (broadcast.toLong() and 0xFFFFFFFFL) - (network.toLong() and 0xFFFFFFFFL) - 1L
+        if (count < 1L || count > 65534L) return emptyList()
+        var i = network + 1
+        val last = broadcast - 1
+        while (true) { out.add(i); if (i == last) break; i++ }
+        return out
+    }
+
+    /** "192.168.1.50" -> 32-Bit-Int (big-endian), null bei ungueltig */
+    private fun ipv4ToInt(s: String): Int? {
+        val o = s.split('.')
+        if (o.size != 4) return null
+        var v = 0
+        for (part in o) {
+            val n = part.toIntOrNull() ?: return null
+            if (n < 0 || n > 255) return null
+            v = (v shl 8) or n
+        }
+        return v
+    }
+
+    /** 32-Bit-Int (big-endian) -> "192.168.1.50" */
+    private fun intToIpv4(i: Int): String =
+        "${(i shr 24) and 0xFF}.${(i shr 16) and 0xFF}.${(i shr 8) and 0xFF}.${i and 0xFF}"
+
     /* --------------------------------------------------------------------- */
     /* Port-Scan                                                              */
     /* --------------------------------------------------------------------- */