1. Problem Overview
The IWLAN/PB Link PN IO (article number 6GK1417-5AB00) is a compact industrial router that bridges Industrial Wireless LAN (IWLAN) with PROFIBUS DP and PROFINET IO. It is commonly used to attach remote PROFIBUS slaves (e.g., ET 200S with IM 151-1) to a PROFINET controller over an 802.11 a/b/g link through a SCALANCE W access point such as the W788-1PRO.
On a fresh-from-the-box unit, a typical failure mode presents as follows:
- SF LED (red): ON continuously
- ON LED (green): flashing slowly (not steady ON)
- The device is not reachable via Edit Ethernet Node in SIMATIC Manager, nor via the Primary Setup Tool (PST), nor via ICMP ping.
- The PROFINET controller CPU (e.g., S7-315-2PN/DP) reports a diagnostic buffer entry such as "Station failure" or "Cannot access module" for the wireless link.
The slow-flashing ON LED plus a solid SF LED is the canonical signature of a device that has completed power-on self-test but is stuck in STOP / system error and has not yet been commissioned with a valid WLAN configuration. In the field, this is almost always a configuration problem, not a hardware fault, and is correctable without RMA.
2. Hardware Identification and LED States
Confirm the exact article number and firmware version before troubleshooting. The relevant variants share the prefix 6GK1417-5AB but differ in firmware revision and approvals.
| Article No. | Firmware | MLFB Revision | Notes |
|---|---|---|---|
| 6GK1417-5AB00 | V1.1 | 1 | Original release. Known to exhibit SF LED on first startup if not commissioned. |
| 6GK1417-5AB00 | V1.3 | 2 | Recommended upgrade; addresses startup/SSID behavior issues. |
| 6GK1417-5AB01 | V2.0 | — | Later hardware revision, improved diagnostics. |
Decoding the LED matrix is the fastest first diagnostic. Refer to the operating instructions IWLAN/PB Link PN IO Manual (MN_Iwlanlink_76.pdf).
| LED | Color | State | Meaning | Action |
|---|---|---|---|---|
| ON | Green | ON steady | Power OK, firmware running, link operationally ready | None — proceed to STEP 7 configuration |
| Green | Flashing slow (~0.5 Hz) | Device in STOP / no valid configuration / waiting for commissioning | Perform first startup with PST or STEP 7 | |
| — | OFF | No power or hardware defect | Check 24 V supply on terminal block | |
| SF | Red | ON steady | System fault, group error, PROFINET/PROFIBUS diagnostic pending | Read diagnostic buffer via Web Based Management (WBM) |
| — | OFF | No fault | None | |
| WLAN | Green | Flashing | WLAN data traffic present | None |
| PB / PN | Green | ON/Flashing | PROFIBUS or PROFINET link state | Cross-check with PLC diagnostic buffer |
3. System Topology and Network Architecture
The wireless PROFINET island that the source describes uses three distinct network layers. The IWLAN/PB Link is acting as a PROFINET IO device and as a PROFIBUS gateway simultaneously. This dual role is the source of most first-time-commissioning confusion.
+-------------------+ PROFINET +-----------------+ WLAN +-------------------+
| CPU 315-2PN/DP | <----------> | SCALANCE W788-1 | <------> | IWLAN/PB Link |
| (IO Controller) | (PN/PN) | PRO (AP) | 802.11g | PN IO 6GK1417-5 |
+-------------------+ +-----------------+ +---------+---------+
| PROFIBUS DP
v
+-----------------+
| IM 151-1 (Std) |
| + PM-E + 8DI |
| + 8DO |
+-----------------+
Key architectural constraints from the TIA Portal documentation Configuration using IWLAN/PN link (TIA Portal V20):
- When multiple IWLAN/PB links share one WLAN segment, they must share the available wireless bandwidth. There is no per-link QoS on 802.11g at the application layer.
- The IWLAN/PB Link has exactly one PROFINET port and exactly one PROFIBUS master interface. As a PN device it accepts a single AR (Application Relationship) from one IO controller.
- The PROFINET device name must be unique on the subnet, including across the wireless bridge. Two identical names on the WLAN side will trigger an SF LED on at least one device.
- The default shipped PROFINET device name is
IWLAN-PB-Link-PN-IO. If two unconfigured devices boot on the same AP, they will collide.
4. First Startup Configuration Procedure
When the IWLAN/PB Link is shipped, it is pre-configured to associate with the SSID WLAN_CONFIG_AP. The configuration AP must be operated in a specific mode to allow this initial association.
4.1 Prerequisites
- SCALANCE W788-1PRO set to factory defaults
- Country code:
Germany(regulatory domain) - Security: Open System (no WPA/WPA2, no 802.1X)
- iPCF disabled (iPCF is for PROFINET-over-WLAN deterministic roaming and must be OFF during commissioning)
- Mode:
802.11g(mixed b/g acceptable for V1.x firmware) - SSID:
WLAN_CONFIG_AP
4.2 Step-by-Step First Startup
- Power the SCALANCE W788-1PRO and the IWLAN/PB Link PN IO. Verify 24 V DC on the Link's power terminals (terminals 1L+, 2L+).
- Verify the W788-1PRO LEDs:
L1/L2link,P1power,R1ready should all be ON with no fault pattern. - From a PG/PC, launch the Primary Setup Tool (PST) or use STEP 7 PLC > Edit Ethernet Node > Browse to discover the link on the wired side of the AP.
- The IWLAN/PB Link should appear in the browse list with MAC address prefix
00-0E-8C(Siemens SCALANCE/IWLAN OUI). Select the device. - Assign an IP address, subnet mask, and a unique PROFINET device name (e.g.,
iwlan-pb-link-01). Click Assign Name. - Verify ICMP reachability:
ping <assigned-IP>from the PG. A reply confirms the WLAN association and IP stack. - Open the Web Based Management (WBM) at
https://<IP>and check:- Information > WLAN > Associated Clients — the link should be listed.
- Information > PROFINET > Device Name — must match the name assigned in step 5.
- Diagnostics > System > Log Table — read any SF LED cause codes.
5. Resetting the IWLAN/PB Link PN IO
If the device was previously configured with a wrong SSID, name, or IP, the reset procedure is documented in the operating instructions. Locate the recessed RESET button behind the front panel.
- Power the device ON.
- Press and hold the RESET button for more than 10 seconds (firmware V1.1 / V1.3) with a paper clip or pin.
- Release the button. The device will reboot and restore the factory defaults (SSID
WLAN_CONFIG_AP, no PROFINET name, no IP, Open System). - Re-apply the first-startup procedure from section 4.
If the ON LED does not return to slow-flash (commissioning mode) within 30 seconds of the reset release, the firmware is corrupted or the device has a hardware fault. In that case proceed to the firmware recovery in section 9 before declaring RMA.
6. WLAN Configuration Parameters
After successful first startup, reconfigure both ends of the wireless link to the production values. Mismatches between AP and client are the single most common cause of an SF LED after a successful ping.
| Parameter | SCALANCE W788-1PRO (AP) | IWLAN/PB Link (Client) | Mandatory Match |
|---|---|---|---|
| SSID | Plant_SSID (e.g., PLANT_WLAN_01) |
Same | YES |
| Channel / Frequency | 2.4 GHz band, fixed channel (see section 7) | Auto-scan, must lock to AP channel | Channel must be in AP coverage |
| Security | WPA2-PSK (AES) recommended | WPA2-PSK (AES) with same passphrase | YES |
| Country Code | Germany (or local regulatory) | Same | YES |
| iPCF | Disabled for commissioning | Disabled | Match |
| Max. Tx Power | Per regional regulations | Per regional regulations | Match |
| DTIM / Beacon | Default 100 ms / 100 ms | n/a (client) | — |
7. Multi-AP Channel Planning on 2.4 GHz
Six access points at the same site on 2.4 GHz is a high-density WLAN scenario. The 2.4 GHz ISM band in Europe (ETSI EN 300 328) provides 13 channels, but the 802.11g channel bandwidth is 22 MHz, leaving only three non-overlapping channels: 1, 6, and 11. Any other assignment guarantees co-channel or adjacent-channel interference.
A reported 76% overlap from one AP onto the other five is an unambiguous indication that Auto Channel Select has chosen a frequency that lies on top of (or directly adjacent to) the channels in use by the other five APs.
7.1 Channel Plan for Six APs
With only three non-overlapping channels, six APs must be deployed on a re-use pattern. Assign fixed channels, do not leave them on auto:
| AP ID | Fixed Channel (2.4 GHz) | Center Frequency (MHz) | Adjacent-AP Separation |
|---|---|---|---|
| AP-01 | 1 | 2412 | > 25 m line-of-sight from AP-02 / AP-03 |
| AP-02 | 6 | 2437 | > 25 m from AP-01 / AP-03 |
| AP-03 | 11 | 2462 | > 25 m from AP-01 / AP-02 |
| AP-04 | 1 | 2412 | Reuse of AP-01 channel; non-co-located |
| AP-05 | 6 | 2437 | Reuse of AP-02 channel; non-co-located |
| AP-06 | 11 | 2462 | Reuse of AP-03 channel; non-co-located |
7.2 Handoff and Roaming Behavior
When the IWLAN/PB Link roams between APs on the same SSID, it must re-associate on the new channel. On V1.1 firmware this re-association can take 1–3 seconds during which PROFINET I/O updates are stalled. Symptoms on the PLC:
- Brief station failure messages in the CPU diagnostic buffer
- Temporary I/O substitution values
- If watchdog is set < 3 s on the I-device: SF LED on the IO controller
3 × send-clock minimum, and the send-clock to 1 ms (or higher). On V1.3 firmware, iPCF (if enabled) reduces roaming time to < 50 ms, but iPCF requires matching configuration on both AP and client and disables standard 802.11 client behavior.7.3 Path-Loss Budget for a 76% Overlap Case
If a single AP's signal is present at 76% of the strength at five neighbor locations, the cell is far too large. Expected free-space path loss at 2.4 GHz over 30 m line of sight is approximately:
FSPL(dB) = 32.45 + 20·log10(2437 MHz) + 20·log10(0.030 km) ≈ 32.45 + 67.7 + (−30.5) = 69.7 dB
At received-signal levels above approximately −65 dBm the client will hold association. To force proper handoff, lower the AP transmit power to ~10 dBm (10 mW) and aim for cell overlap of 15–20% between adjacent APs, not 76%.
8. PROFINET IO Configuration as Gateway + PN Device
When the IWLAN/PB Link is used both as a PROFINET IO device on the PN side and as a PROFIBUS master on the DP side, two PROFINET device names and one IP are still required. Only the PN port participates on PROFINET; the DP port is a master, not a device.
8.1 HW Config in STEP 7 (Classic)
- Open SIMATIC Manager and load the station with the CPU 315-2PN/DP.
- In HW Config, drag the IWLAN/PB Link PN IO from the catalog under PROFINET IO > Network components > IWLAN > IWLAN/PB Link PN IO onto the PROFINET subnet.
- Assign a unique PROFINET device name (e.g.,
iwlan-pb-link-01). Do not leave the default nameIWLAN-PB-Link-PN-IOon more than one device in the subnet. - Assign the IP address and subnet mask.
- Configure the PROFIBUS master side: slot 4 of the IWLAN/PB Link is the DP master port. Add IM 151-1 and its I/O modules to the DP slave list.
- Compile and download the HW Config to the CPU 315-2PN/DP.
8.2 GSD-based PROFIBUS Slaves
If the DP side carries third-party slaves, install the IWLAN/PB Link GSD file and use it as a DP master proxy. The PROFIBUS master parameters on the IWLAN/PB Link default to address 1, baud rate 1.5 Mbit/s auto-detect. For a single IM 151-1 standard, 1.5 Mbit/s is preferred over 12 Mbit/s for first-startup stability.
9. Firmware Upgrade to V1.3
Siemens shipped a maintenance firmware (V1.3) for the 6GK1417-5AB00 that addresses early-life SSID-association problems and improves WBM diagnostics. Upgrade is performed via TIA Portal / STEP 7 or via the WBM file upload.
- Download the firmware package from the Siemens Industry Online Support entry ID 38616756.
- Open the WBM of the IWLAN/PB Link at
https://<IP>as user admin. - Navigate to System > Firmware Update and select the downloaded
*.updfile. - Confirm the update. The device reboots twice during the procedure. Total time ~3 minutes.
- After reboot, verify in WBM Information > System > Device > Firmware Version that V1.3 is active.
- Re-apply the configuration (PROFINET name, IP, WLAN SSID) — firmware updates do not preserve the user configuration on V1.x.
10. Diagnostic Procedures and WBM Access
The WBM is the primary diagnostic surface for the IWLAN/PB Link. Access it directly via the wired Ethernet port of the device when troubleshooting a wireless SF.
| WBM Path | Information | Healthy Value |
|---|---|---|
| Information > Start Page | Firmware, MLFB, serial | V1.3, 6GK1417-5AB00, non-zero S/N |
| Information > WLAN > Client List | Associated AP, RSSI in dBm | RSSI > −70 dBm, AP MAC matches expected |
| Information > PROFINET > Device Name | PROFINET name | Unique, matches HW Config |
| Diagnostics > System > Log Table | Event log with timestamps | No "System error" / "PROFINET AR rejected" |
| Diagnostics > PROFINET > Alarms | PN diagnostics | Empty in steady state |
| Diagnostics > PROFIBUS > Diagnostics | DP slave list and states | All slaves in Data Exchange |
10.1 RSSI Interpretation
| RSSI | Link Quality | Action |
|---|---|---|
| > −55 dBm | Excellent | None |
| −55 to −67 dBm | Good | None |
| −68 to −75 dBm | Marginal | Reduce AP coverage area or add AP |
| < −75 dBm | Unreliable | Re-design RF path; add repeater |
11. Troubleshooting Matrix
| Symptom | Likely Root Cause | Diagnostic Step | Corrective Action |
|---|---|---|---|
| ON LED slow-flash, SF ON, no IP, no ping | Factory default, no commissioning yet | Connect to AP SSID WLAN_CONFIG_AP, browse with PST |
Assign IP and PROFINET name per section 4 |
| ON LED slow-flash, SF ON, IP assigned, no ping | SSID mismatch or wrong country code | WBM > Information > WLAN > Client List | Reset (section 5) and re-commission |
| ON LED steady, SF ON, ping OK | PROFINET name conflict or wrong IO controller | WBM > PROFINET > Device Name; CPU diagnostic buffer | Assign unique PROFINET name; verify AR in HW Config |
| ON steady, SF ON, AR established, DP slaves not in Data Exchange | PROFIBUS address conflict or wrong baud | WBM > PROFIBUS > Diagnostics; check IM 151-1 address | Set unique DP addresses 1–125, fix baud rate |
| ON steady, SF OFF, but PLC sees station failure intermittently | AP overlap / co-channel interference > 50% | AP WBM > Information > WLAN > Neighbor APs; RSSI from client | Apply channel plan (section 7); reduce AP Tx power to 10 dBm |
| ON LED OFF | No 24 V supply or hardware defect | Measure 24 V on terminal block | Restore supply; if voltage correct, suspect hardware |
| Reset button does not restore defaults | Firmware corruption | — | Perform firmware update via WBM in safe mode (hold RESET during power-on for > 30 s) |
| SF LED returns 30 s after reset, ON never steady | Wrong PROFINET configuration downloaded, e.g., duplex mismatch | Read CPU diagnostic buffer | Delete device from HW Config, re-add, recompile and re-download |
12. Field-Proven Caveats
- Two brand-new IWLAN/PB Links powered on against the same configuration AP will both advertise the default PROFINET name. The first to be commissioned by PST wins. Always commission sequentially, not in parallel.
- The W788-1PRO on Auto Channel Select is the single largest source of the 76% overlap symptom. Even in 5-AP installations, auto-channel produces co-channel collisions within 24 hours of operation as RSSI profiles shift with temperature and humidity.
- CPU 315-2PN/DP, when used as the IO controller with an IWLAN/PB Link as a PN device, must have its send-clock set to a value supported by the Link. Default is 1 ms, which is fine for V1.3 firmware. V1.1 firmware occasionally drops to 2 ms after a few warm reboots — verify with PLC > Diagnostic > PROFINET.
- iPCF (industrial Point Coordination Function) is a Siemens proprietary extension that reduces roaming time below 50 ms but requires both AP and client to have it enabled. Do not enable iPCF on the client only; it will refuse to associate with a standard AP and the SF LED will return.
- When migrating from 802.11g to 802.11n on the W788-1PRO, the IWLAN/PB Link V1.x cannot follow. It will stay associated at 54 Mbit/s while the AP advertises HT rates, wasting airtime. The mixed-mode behavior is correct but the bandwidth math must be re-done.
13. Verification Checklist After Repair
- ON LED steady green, SF LED off.
- PG can
ping <IP>with < 5 ms latency. - WBM accessible at
https://<IP>as admin. - WBM > WLAN shows the production AP as associated, RSSI > −70 dBm.
- WBM > PROFINET shows correct device name and an active AR to the CPU.
- WBM > PROFIBUS shows the IM 151-1 in state Data Exchange.
- STEP 7 PLC > Accessible Nodes shows the CPU, AP, and IWLAN/PB Link.
- CPU diagnostic buffer shows no further Station failure events over a 30-minute observation window.
- Force a PROFIBUS fault (e.g., unplug one of the IM 151-1 modules) and verify that the SF LED on the IWLAN/PB Link lights and a corresponding alarm appears in the CPU diagnostic buffer. Restore the module and verify the SF LED clears within the configured PROFINET update timeout.
What does a slow-flashing ON LED plus solid SF LED mean on a 6GK1417-5AB00?
The device is in STOP / no-valid-configuration state. It has finished its power-on self-test but has not been commissioned. Connect a PG to the same WLAN as the configuration AP (SSID WLAN_CONFIG_AP, Open System, no iPCF) and assign an IP plus a unique PROFINET device name using STEP 7 or the Primary Setup Tool.
How do I reset the IWLAN/PB Link PN IO to factory defaults?
Press and hold the recessed RESET button on the front panel for more than 10 seconds while the device is powered, then release. The link will reboot with default SSID WLAN_CONFIG_AP, no PROFINET name, and no IP. The ON LED should return to slow-flash within 30 seconds.
Which 2.4 GHz channels should I use for six SCALANCE W access points?
Use only the three non-overlapping channels 1, 6, and 11 (center frequencies 2412, 2437, 2462 MHz). Assign them in a 1-6-11-1-6-11 re-use pattern, set each AP to a fixed channel, and lower the transmit power so adjacent cells overlap by 15-20%, not 76%.
Does the IWLAN/PB Link need a unique PROFINET device name if it is used only as a PROFIBUS gateway?
Yes, when it is also a PROFINET IO device on the PN side. The PN port accepts exactly one Application Relationship from one IO controller, and the name must be unique across the entire PROFINET subnet including the wireless segment. Duplicate names trigger an SF LED on the affected link.
Should I upgrade the 6GK1417-5AB00 from V1.1 to V1.3?
Yes, if the device still ships with V1.1. Firmware V1.3 improves SSID association behavior, expands the WBM diagnostic detail, and is required for clean operation with current TIA Portal versions. Download the update from Siemens Industry Online Support entry 38616756 and apply it via the WBM.