SCALANCE XC208 Red Fault LED: Restoring PROFINET Defaults

Overview: SCALANCE XC208 Fault LED Symptom

The SCALANCE XC208 (Siemens order number 6GK5208-0BA00-2AB2) is a managed 8-port industrial Ethernet switch designed for PROFINET and standard Ethernet networks on the shop floor. As a managed PROFINET IO device, it participates in PROFINET diagnostics, exposes a GSDML file to engineering tools, and is configured primarily through Siemens TIA Portal, PRONETA, or the integrated Web-Based Management (WBM).

When the front-panel fault LED lights steady red and remains lit (does not flash), the switch has detected an unrecoverable or persistent error condition. This is distinct from a blinking fault LED, which typically indicates a transient or recoverable event. A solid red fault LED disables the PROFINET AR (Application Relationship) handshake, so the controller cannot establish cyclic IO data exchange with the switch. In TIA Portal, the device appears with a red "unreachable" status; in PRONETA, the device disappears from the topology scan; and the WBM continues to serve HTTP/HTTPS but shows an "Error" banner at the top of every page.

The recovery procedure that consistently clears this condition is to invoke the WBM command "Restart with PROFINET Defaults" while connected to the switch via the standard Ethernet (not PROFINET) channel, then re-assign the PROFINET device name with PRONETA. Escalation steps for C-PLUG, power, and link-down faults are documented below.

SCALANCE XC208 Hardware and PROFINET Role

The XC208 occupies the middle of the SCALANCE X-200 family and supports both layer-2 switching and PROFINET IO device mode. Relevant baseline specifications are summarized below.

The fault LED is the red indicator labelled "F" (or "Fault") on the lower row of the front panel. While the switch is booting the fault LED briefly illuminates red, then extinguishes once PROFINET AR and the C-PLUG have initialized cleanly. A persistent solid red state after boot means one of the conditions in the next section is active.

Reference: SCALANCE X-200 Operating Instructions (PDF).

Solid Red Fault LED: Root Cause Matrix

According to the SCALANCE X-200 operating instructions, a solid red fault LED signals one of four underlying events. The WBM exposes the same events through the top-of-page "Error" banner described in the TIA Portal Cloud documentation for SCALANCE X.

In the field case where TIA Portal reports the device as unreachable and PRONETA cannot even see the device during a topology refresh, the most likely root cause is the fourth category - PROFINET stack inconsistency (often a corrupted PROFINET name, duplicate PROFINET name in the network, or a stale IO configuration). This is the case that the WBM "Restart with PROFINET Defaults" function is designed to clear.

References: SCALANCE X-200 Operating Instructions, TIA Portal Cloud - Fault display for SCALANCE X.

Prerequisites Before the Reset

Before invoking the WBM reset, complete the following to avoid cascading the fault into another device:

1. Verify the management PC has an IP address on the same subnet as the XC208 (default 192.168.1.100 / 255.255.255.0). Configure a static IP such as 192.168.1.50 if no DHCP server is available.
2. Disconnect the XC208 from the live PROFINET ring. A solid red fault LED will disrupt AR handshakes on connected controllers; isolating the switch prevents the PLC from logging a station failure that masks the recovery.
3. Keep one patch cable connected between the PC and any XC208 RJ-45 port (P1-P8). The fault LED typically persists even with only the PG connected - this is normal during the recovery phase and is documented further below.
4. Confirm the management PC can ping 192.168.1.100. If the ping fails, connect directly and disable any firewall that blocks ICMP; some switches will not respond to ICMP until the PROFINET stack has reset.
5. Identify a recent project backup or the GSDML file for the XC208. After the reset, you will need to reassign the PROFINET device name and re-import the IO configuration in TIA Portal.

Step-by-Step: Restore PROFINET Defaults via WBM

The XC208 ships with a built-in Web-Based Management interface that runs on TCP/80 (HTTP) and TCP/443 (HTTPS). When the PROFINET stack is degraded but the switch is still forwarding frames, the WBM remains accessible through the standard Ethernet path. Use the following procedure to clear the PROFINET state.

1. Open a browser (Chrome, Firefox, or Edge - Internet Explorer is deprecated in TIA Portal V18+) and navigate to https://192.168.1.100 (or the IP you assigned via PRONETA earlier). Accept the self-signed certificate warning.
2. Log in with the configured credentials. Default credentials for a factory-fresh XC208 are admin / admin; if the password was changed during commissioning, use the current one.
3. In the WBM menu, navigate to System > Restart. Two restart options are presented:
   • Restart with default settings - full factory reset of all IP, PROFINET, and switching parameters.
   • Restart with PROFINET defaults - resets only the PROFINET device name, IO configuration, and PROFINET AR state. IP, switch ports, SNMP, and other settings are preserved.
4. Select Restart with PROFINET defaults and confirm the dialog. The switch will reboot, which takes 30-60 seconds. Do not power-cycle the device during this window.
5. After the reboot, the fault LED should extinguish within 5 seconds of boot completion. If the LED remains lit, repeat the procedure once; if the second attempt fails, escalate to the C-PLUG and power checks below.

Reassign the PROFINET Device Name with PRONETA

Once the fault LED has cleared, the XC208 no longer has a PROFINET device name, so the PLC will still mark it as unreachable. Use PRONETA (Siemens network commissioning and diagnostics tool, available free of charge from the Siemens Industry Online Support) to reassign the name.

1. Launch PRONETA on the management PC. Versions 3.x and newer support all SCALANCE X-200 switches including the XC208 and integrate with TIA Portal V16 through V20.
2. Click Network analysis and start a discovery scan. The XC208 should appear in the device list with a yellow status (no PROFINET name assigned).
3. Select the XC208 row and click Assign PROFINET name. Enter the exact device name as it is configured in the TIA Portal project (e.g., sw-cab-208). The name is case-sensitive and must match exactly.
4. Confirm the assignment. PRONETA writes the name into the switch's PROFINET stack via DCP and verifies by reading it back.
5. Reconnect the XC208 to the live PROFINET ring. The PLC should establish an AR within 10 seconds and clear the station failure diagnostic.

Verification Checklist

After the reset and name reassignment, verify the recovery with the following matrix:

Why the Fault LED Stays Lit With Only the PG Connected

A subtle observation that often confuses first-time operators is that the fault LED remains solid red even when every PROFINET cable is disconnected and only the engineering PG is patched into one RJ-45 port. This is expected behavior, not a separate fault.

The PROFINET stack on the XC208 reports a fault whenever it has not established an AR with a PROFINET controller. When the switch is isolated from the controller (only the PG is connected, or the controller is in STOP), the stack cannot form an AR and therefore reports a permanent fault. The fault LED is essentially summarizing "PROFINET not operational." Once a controller comes online and the AR is established, the LED clears.

To distinguish this benign state from a true fault:

• Check the WBM. If the "Error" banner shows a C-PLUG, power, or link-down entry, the fault is real. If the banner is empty or shows only "PROFINET not connected," it is the benign AR-pending state.
• Use PRONETA topology discovery. The switch will appear with status "PROFINET device, no name assigned" or "PROFINET device, AR pending" - both are non-error conditions.
• Temporarily plug the XC208 into a known-good controller and watch the fault LED. If it clears within 30 seconds, the prior red state was AR-pending, not a hard fault.

C-PLUG, Power, and Link-Down Subsystem Checks

If the WBM reset does not extinguish the fault LED, escalate to the underlying subsystems:

1. Power supply check. Measure 24 VDC at terminals L1/M1 and L2/M2 (if redundant) under load. Voltage must remain above 19.2 V at the terminal. The XC208 will tolerate brief sags but will latch the fault LED if the voltage drops below the threshold for more than approximately 20 ms.
2. C-PLUG integrity. Open WBM > System > C-PLUG. The status should read "OK" with the configuration version and slot count. If it reads "not present," reseat the C-PLUG. If it reads "defect" or "write-protect error," replace the C-PLUG (Siemens part 6GK1900-0AB00). Note that a corrupt C-PLUG can keep the fault LED lit even after a PROFINET-defaults reset, because the stack cannot persist the new clean state.
3. Link-down on monitored port. Open WBM > Information > Topology Discovery and confirm that all expected neighbor ports are "up." A monitored port in the "down" state will latch the fault LED until the link is restored or the port is removed from the monitored set under Layer 2 > Topology Discovery.
4. Firmware mismatch. If the switch was upgraded to a newer PROFINET conformance class (e.g., from CC-B to CC-C) but the controller still expects the older one, the AR handshake fails and the fault LED stays red. Roll back the firmware or update the GSDML import in TIA Portal to match.

TIA Portal Re-Integration Procedure

If TIA Portal still shows the XC208 as unreachable after the WBM reset and the PRONETA name assignment, perform the following:

1. In the TIA Portal project tree, right-click the XC208 device and select Online & Diagnostics > Assign PROFINET device name.
2. Click Update list to trigger a DCP discovery. The XC208 should appear with its newly assigned PROFINET name.
3. Select the device and click Assign name. Confirm the IO controller assignment (the S7-1500 / S7-1200 CPU that owns the AR).
4. Compile and download the device configuration if TIA Portal reports a configuration mismatch. This is sometimes required after the reset because the WBM-cleared PROFINET state no longer matches the project's expected slot configuration.
5. Open Online & Diagnostics for the XC208 and verify that the diagnostic buffer is empty and the maintenance status is "OK."

Reference: TIA Portal Cloud - Fault display for SCALANCE X (V20).

Firmware and C-PLUG Recovery Notes

When the WBM reset, C-PLUG reseat, and power checks all fail to clear the fault LED, the next escalation is firmware-level recovery:

1. Use SIMATIC Automation Tool or the Siemens primary setup tool (PST) to load a known-good firmware image (e.g., V6.5.x for SCALANCE X-200) via the service interface.
2. After the firmware load completes, the switch boots with default IP 192.168.1.100. Reapply the IP, subnet, and gateway via PRONETA or the WBM.
3. Reassign the PROFINET device name as described above.
4. Re-import the GSDML into TIA Portal and re-download the IO configuration.

FAQ