diff --git a/backend/modules/network_scanner.py b/backend/modules/network_scanner.py
new file mode 100644
index 0000000..f9c4d53
--- /dev/null
+++ b/backend/modules/network_scanner.py
@@ -0,0 +1,78 @@
+import asyncio
+import subprocess
+from typing import Any
+
+
+class NetworkScanner:
+    def __init__(self, subnet: str):
+        self.subnet = subnet
+
+    def scan(self) -> dict[str, Any]:
+        import nmap
+        nm = nmap.PortScanner()
+        nm.scan(hosts=self.subnet, arguments="-sn")
+        return {"scan": dict(nm._scan_result.get("scan", {}))}
+
+    def parse_scan_results(self, scan_data: dict[str, Any]) -> list[dict[str, Any]]:
+        nodes = []
+        for ip, data in scan_data.get("scan", {}).items():
+            hostnames = data.get("hostnames", [{}])
+            hostname = hostnames[0].get("name", "") if hostnames else ""
+            vendors = data.get("vendor", {})
+            vendor = next(iter(vendors.values()), "") if vendors else ""
+            nodes.append({
+                "ip": ip,
+                "hostname": hostname,
+                "status": data.get("status", {}).get("state", "unknown"),
+                "vendor": vendor,
+            })
+        nodes.sort(key=lambda n: tuple(int(p) for p in n["ip"].split(".")))
+        return nodes
+
+    def merge_with_config(
+        self,
+        discovered: list[dict[str, Any]],
+        configured: list[dict[str, Any]],
+    ) -> list[dict[str, Any]]:
+        config_by_ip = {n["ip"]: n for n in configured}
+        merged = []
+        seen_ips = set()
+
+        for node in discovered:
+            ip = node["ip"]
+            seen_ips.add(ip)
+            if ip in config_by_ip:
+                entry = {**config_by_ip[ip], **{"status": node["status"], "auto_discovered": True}}
+            else:
+                entry = {
+                    "name": node["hostname"] or ip,
+                    "ip": ip,
+                    "status": node["status"],
+                    "vendor": node.get("vendor", ""),
+                    "icon": "device",
+                    "auto_discovered": True,
+                    "connections": [],
+                }
+            merged.append(entry)
+
+        for node in configured:
+            if node["ip"] not in seen_ips:
+                merged.append({**node, "status": "unknown", "auto_discovered": False})
+
+        return merged
+
+    async def ping_host(self, ip: str) -> bool:
+        try:
+            proc = await asyncio.create_subprocess_exec(
+                "ping", "-c", "1", "-W", "1", ip,
+                stdout=subprocess.DEVNULL,
+                stderr=subprocess.DEVNULL,
+            )
+            code = await proc.wait()
+            return code == 0
+        except Exception:
+            return False
+
+    async def ping_all(self, ips: list[str]) -> dict[str, bool]:
+        results = await asyncio.gather(*[self.ping_host(ip) for ip in ips])
+        return dict(zip(ips, results))
diff --git a/backend/tests/test_network_scanner.py b/backend/tests/test_network_scanner.py
new file mode 100644
index 0000000..a4367e8
--- /dev/null
+++ b/backend/tests/test_network_scanner.py
@@ -0,0 +1,70 @@
+import pytest
+from unittest.mock import AsyncMock, MagicMock, patch
+from modules.network_scanner import NetworkScanner
+
+
+@pytest.fixture
+def scanner():
+    return NetworkScanner(subnet="192.168.1.0/24")
+
+
+def test_parse_scan_results(scanner):
+    mock_scan_result = {
+        "scan": {
+            "192.168.1.1": {
+                "status": {"state": "up"},
+                "hostnames": [{"name": "router.local", "type": "PTR"}],
+                "vendor": {"AA:BB:CC:DD:EE:FF": "Cisco"},
+            },
+            "192.168.1.10": {
+                "status": {"state": "up"},
+                "hostnames": [{"name": "", "type": ""}],
+                "vendor": {},
+            },
+        }
+    }
+
+    nodes = scanner.parse_scan_results(mock_scan_result)
+    assert len(nodes) == 2
+    assert nodes[0]["ip"] == "192.168.1.1"
+    assert nodes[0]["hostname"] == "router.local"
+    assert nodes[0]["status"] == "up"
+    assert nodes[1]["ip"] == "192.168.1.10"
+
+
+def test_merge_with_config(scanner):
+    discovered = [
+        {"ip": "192.168.1.1", "hostname": "router.local", "status": "up", "vendor": "Cisco"},
+        {"ip": "192.168.1.50", "hostname": "", "status": "up", "vendor": ""},
+    ]
+    configured = [
+        {
+            "name": "Router Principal",
+            "ip": "192.168.1.1",
+            "username": "admin",
+            "password": "pass",
+            "icon": "router",
+            "connections": [],
+        },
+    ]
+
+    merged = scanner.merge_with_config(discovered, configured)
+    # Router should have config data merged in
+    router = next(n for n in merged if n["ip"] == "192.168.1.1")
+    assert router["name"] == "Router Principal"
+    assert router["username"] == "admin"
+    assert router["status"] == "up"
+    # Unknown device keeps discovered data
+    unknown = next(n for n in merged if n["ip"] == "192.168.1.50")
+    assert unknown["name"] == "192.168.1.50"
+    assert unknown.get("username") is None
+
+
+@pytest.mark.asyncio
+async def test_ping_host(scanner):
+    with patch("asyncio.create_subprocess_exec", new_callable=AsyncMock) as mock_exec:
+        mock_proc = MagicMock()
+        mock_proc.wait = AsyncMock(return_value=0)
+        mock_exec.return_value = mock_proc
+        result = await scanner.ping_host("192.168.1.1")
+        assert result is True