CPU1507S Nanobox IPC: Resolving the X2 Network Interface Not Visible in Windows

The Siemens SIMATIC Nanobox IPC paired with the CPU 1507S software controller is a compact PROFINET-capable automation platform. A frequent commissioning symptom is that the secondary network interface (X2) appears in Windows Device Manager on first boot, then disappears after the TIA Portal project is loaded. Engineers expect two NICs to remain visible because they intend to use one for the Windows engineering station and the other for the PLC's PROFINET ring. Instead, only the X1 adapter remains, the CPU 1507S webserver stops responding on the X2 IP, and OPC UA traffic appears to drop silently. This article documents the root cause, the verification path, and the working configurations for webserver and OPC UA access.

1. Problem Statement

Typical field report after loading the TIA Portal project to the CPU 1507S:

• X1 (Windows side) IP is reachable, e.g. 192.168.0.10 / 255.255.255.0.
• X2 (PLC side) IP is configured in TIA Portal, e.g. 192.168.0.11, but Windows does not list X2 in Device Manager.
• ping 192.168.0.11 from the Nanobox itself returns Destination host unreachable.
• The CPU 1507S webserver is not reachable on http://192.168.0.11 but responds on http://localhost:81.
• OPC UA clients cannot connect to opc.tcp://192.168.0.11:4840.

Initial assumption is a driver or firewall issue. The actual root cause is a deliberate hardware-assignment design choice of the CPU 1507S runtime.

2. System Architecture of the Nanobox + CPU 1507S

The SIMATIC CPU 1507S is the software controller variant of the S7-1500 family. On a Nanobox IPC (e.g. SIMATIC IPC227G or IPC277G), the runtime is a hardened Windows service that takes exclusive ownership of one physical Ethernet port.

The runtime registers X2 as a PROFINET interface and unbinds it from the Windows TCP/IP stack. From that moment, X2 is invisible to ipconfig, Get-NetAdapter, and Device Manager. This is the same pattern as the S7-1500 Software Controller system manual documents for all supported IPC platforms.

3. Root Cause: Exclusive NIC Assignment is a Design Feature

The CPU 1507S is engineered to give the PLC an isolated, deterministic network path that the Windows OS cannot interrupt. Even if Windows crashes, blue-screens, or is being patched, the X2 link and any PROFINET devices behind it remain reachable from the runtime. The trade-off is that you cannot use X2 as a Windows-managed NIC for routing, ICMP, or shared Ethernet.

Implications for engineers who expect two visible NICs:

• No arp -a entry will show X2's MAC from the Windows stack.
• No Windows Firewall rule can be applied to X2 because the firewall cannot bind to it.
• No tracert or pathping from Windows will traverse X2.
• Any service hosted by the runtime (webserver, OPC UA, S7 communication, PROFINET) is reachable on the X2 IP only from devices physically attached to X2.

4. Initial Diagnostic Steps

Run the following on the Nanobox IPC before changing any configuration. They confirm the runtime is healthy and that X2 is correctly bound.

1. Verify the runtime is started. Open Windows Services (services.msc) and confirm Siemens SIMATIC S7-1500 Software Controller is in state Running.
2. Confirm only one NIC is visible to Windows. Open PowerShell and run Get-NetAdapter | Where-Object Status -eq 'Up'. Expect a single Up interface (X1).
3. Read the PLC's own diagnostic pages. Browse to http://localhost:81. If the S7-1500 webserver home page appears, the runtime is fully operational and owns X2.
4. Check TIA Portal online view. In TIA Portal V17 or later, Online > Accessible nodes should list the CPU 1507S by its X2 IP. If it does, the PLC side is alive even when Windows cannot ping it.
5. Inspect the runtime log. The default log location is C:\ProgramData\Siemens\Automation\Logs\S7-1500S. Look for the line PROFINET interface X2 bound.

5. Webserver Access via Localhost

Because X2 is owned by the runtime, the only IP from which the webserver is reachable without extra wiring is the Windows loopback. The runtime publishes the webserver on a loopback-shifted port set so that multiple S7-1500 Software Controllers on the same host do not collide. Typical mappings:

Loopback port mapping is configured per project. To verify or change it, open TIA Portal and navigate to CPU properties > Webserver > Port assignment for engineering access via Windows. After a project download and CPU restart, the new ports are active. Reference: CPU 1507S manual, section on webserver access from the engineering host.

6. Bridging X1 and X2 for External Access

To reach the webserver or OPC UA server from a remote engineering station, SCADA node, or MES server, the Nanobox must bridge or forward between X1 and X2. Two practical approaches are field-proven.

6.1 Physical loopback cable (recommended for bench commissioning)

1. Place an Ethernet patch cable between X1 and X2 on the Nanobox. This is a temporary loopback used only for diagnostics.
2. Set a second IP on the Windows X1 adapter inside the X2 subnet, e.g. 192.168.0.20 / 255.255.255.0.
3. Open http://192.168.0.11 from a browser on the Nanobox. The webserver responds as if you were any external device.
4. Remove the loopback cable before returning the unit to production. Production PROFINET devices must not share the same wire as Windows traffic.

6.2 Routing through a managed switch (production topology)

The managed switch carries two VLANs:

With this layout, an OPC UA client on VLAN 10 reaches opc.tcp://192.168.0.11:4840 through the switch's Layer-3 interface, or more commonly, the CPU 1507S acts as the OPC UA server and a Windows-side OPC UA forwarder on X1 republishes data on a VLAN-10 IP.

7. OPC UA Server Routing Patterns

Two patterns are commonly deployed on a Nanobox + CPU 1507S combination:

7.1 Direct OPC UA to the PLC side

SCADA or HMI connects directly to opc.tcp://192.168.0.11:4840. Works only if the SCADA node is on the X2 subnet or routed through a Layer-3 device.

7.2 Windows-side OPC UA forwarder (preferred)

1. Install an OPC UA server on the Windows side (e.g. Siemens OPC UA Scout or the S7-1500 Software Controller's bundled forwarding service).
2. Bind the forwarder to the X1 IP, e.g. opc.tcp://192.168.1.10:4840.
3. Point the forwarder at the loopback endpoint opc.tcp://localhost:4840 which the runtime already exposes on the loopback interface.
4. SCADA connects to the X1 address and never touches the PROFINET subnet.

8. Subnet Design Best Practices

Avoid putting X1 and X2 in the same subnet. Windows will route all traffic through the lowest-metric interface, which means X2-owned packets never leave the Nanobox.

9. TIA Portal Configuration Verification

Open the device configuration of the CPU 1507S and check these properties:

1. PROFINET interface > Ethernet addresses: IP address = 192.168.0.11, subnet mask = 255.255.255.0, router not required for isolated PROFINET.
2. Webserver > Activate webserver on this module: ticked.
3. Webserver > Permit access via HTTPS: ticked if remote clients use TLS.
4. OPC UA > Server > Activate OPC UA server: ticked. Port default 4840.
5. Protection > Access level: at least Full access (no protection) for engineering diagnostics; switch to password-protected for production.

After every change, perform a full project download (CPU > Download to device > Hardware and software) and restart the runtime. Hot reloads do not always rebind the exclusive NIC cleanly.

10. Advanced Windows Diagnostics

Use these commands to confirm the runtime has bound X2 correctly.

List all NICs including hidden ones:

Inspect the TCP listeners on the loopback interface:

Expect lines such as 127.0.0.1:81 and 127.0.0.1:343 listening under the S7-1500S process ID.

Confirm the runtime process owns X2 at the kernel level:

If Windows still shows X2 as Up, the exclusive-bind step has not happened. Re-trigger it by stopping the runtime, physically unplugging X2, restarting the runtime, and plugging X2 back in. The runtime will claim it on the next PROFINET stack init.

11. Field Commissioning Checklist

Use this list before signing off the Nanobox + CPU 1507S combination.

12. Frequently Asked Questions