Sinumerik 840D sl X127 Routing Fixing Ping and S7 Online Failures

Sinumerik 840D sl X127 Routing: Fixing Ping and S7 Online Failures

The X127 commissioning/service port on Siemens Sinumerik 840D sl Numeric Control Units (NCU 710.3, 720.3, 730.3) is the primary programming interface used by commissioning engineers to connect a programming device (PG) or service laptop directly to the controller. Unlike the system network port (X120) and the company network port (X130), X127 is a point-to-point commissioning interface with DHCP server enabled by default on address range 192.168.215.0/24.

This reference covers the two failure modes reported most often in field service:

1. Ping time expiration to 192.168.215.1 from a PG connected via crossover cable, even when the PG has a valid DHCP lease in the X127 subnet.
2. "Routing error" dialog returned by Sinumerik Operate when a remote diagnostic or service request is issued from the PCU (for example PCU50.5 with Operate 4.5 SP2) across the system network boundary toward X127.

Both symptoms share a common root cause: the NCU firewall blocks the required TCP ports (TCP/102 for S7 communication, TCP/5900 for VNC) on X127, or the inter-NET routing path from the system network to the commissioning subnet is disabled in basesys.ini. The procedures below resolve the issue with safe, vendor-documented configuration changes and a deterministic verification sequence.

1. Affected Hardware, Firmware, and Software Versions

Confirmed against the Sinumerik 840D sl Commissioning Manual (CNC Commissioning 03/2018 edition) and the Basesys Configuration Manual. Always verify the controller's CF card part number (6FC5xxx-xxx) and the Sinumerik Operate software version on the HMI's Setup > General page before applying the procedure.

2. NCU Ethernet Port Architecture and Default Addressing

The NCU 710.3/720.3/730.3 PN exposes three switched Ethernet interfaces, each mapped to a distinct subnet and a specific role within the Sinumerik 840D sl system network topology:

X127 is electrically isolated from X120 and X130 on most NCU revisions. Routing between the three subnets is performed by the NCU's internal IP stack and is gated by the firewall and by the EnableSysNetToIBNForwarding flag. Without explicit configuration the system network (X120) cannot reach the commissioning subnet (X127), and the laptop on X127 cannot see PCUs or MCPs on X120.

If the laptop is patched into X120 instead of X127 (because X120 is the only free port), then X127 is irrelevant for that session: STEP 7 sees the NCU as a system-network node on 192.168.214.1 and does not require any basesys.ini change. The trade-off is shared bandwidth with PCU, MCP, and drive PROFIsafe traffic.

3. Root Cause Analysis: Firewall and Routing on X127

The NCU 7x0.3 runs a Linux-based real-time platform with a host firewall managed through iptables rules compiled from basesys.ini on every boot. Two parameters in basesys.ini directly determine whether STEP 7 (TCP/102) and VNC remote view (TCP/5900) can pass through X127:

1. ActivateFirewallOpenPorts — comma- or space-separated list of TCP/UDP ports allowed on the commissioning interface. Default is empty (all ports closed) for production builds.
2. EnableSysNetToIBNForwarding — boolean flag (0 or 1) that enables IP forwarding from the system network (X120) to the IBN/commissioning subnet (X127). Default is 0.

When either parameter is at its default value, two distinct failure modes appear:

All four symptoms clear once the parameters below are written to the active basesys.ini and the NCU is rebooted, or the firewall service is reloaded via the Operate Diagnostics > TCP/IP Diagnostics page.

4. Pre-Configuration Checklist and Cabling

Complete the following checks before editing basesys.ini:

1. Confirm the NCU is in commissioning mode or that the machine's safety permits parameter changes. Note the active CF card part number (printed on the CF label).
2. Capture a backup copy of the current basesys.ini. The active path is /card/sinumerik/system/basesys.ini for OEM-supplied files, or /oem/sinumerik/basesys.ini for user customizations.
3. Confirm physical cable. A direct laptop-to-X127 connection requires a crossover cable on legacy PG adapters without auto-MDI/MDIX. Modern laptops (built 2010+) negotiate automatically; the green link LED on the NCU's X127 should illuminate within 3 seconds of insertion.
4. Set the PG Ethernet adapter to Obtain an IP address automatically. Confirm with ipconfig /all that the adapter has been assigned an address in 192.168.215.2–254 with mask 255.255.255.0 and gateway 192.168.215.1 after re-plugging the cable.
5. Disable any secondary virtual adapters (Hyper-V, VirtualBox, VPN TAP, etc.) that may intercept the route to 192.168.215.0/24.
6. Disable the host firewall (Windows Defender or third-party) on the PG temporarily for testing, or add explicit rules permitting inbound/outbound ICMP and TCP/102 to 192.168.215.1.
7. Stop the SIMATIC Automation License Manager service if using TIA Portal in parallel with STEP 7, to prevent PLC project lock contention.

5. basesys.ini Configuration Procedure

The basesys.ini file is an ASCII INI-format file read by the Linux boot sequence on the NCU. The recommended workflow is to write a customer-specific copy under /oem/sinumerik/basesys.ini so that original Siemens settings are preserved across CF-card restores.

5.1 Recommended parameter block

Add (or replace) the following [IBN] section. Comments after ; are allowed but must not contain CR/LF line endings other than Unix LF.

; ---------------------------------------------------------------
; Sinumerik 840D sl — X127 commissioning port enable
; File path: /oem/sinumerik/basesys.ini
; ---------------------------------------------------------------
[IBN]
ActivateFirewallOpenPorts=TCP/102 TCP/5900
EnableSysNetToIBNForwarding=1
Debug=0
; ---------------------------------------------------------------

The two settings have these effects:

5.2 Editing on the NCU

1. Open Sinumerik Operate on the HMI or PCU. Navigate to Setup > Password > Set password and enter the manufacturer password if not already unlocked.
2. Insert a USB stick formatted FAT32 with a known label (for example SINU_USB). Operate mounts it under /tmp/usb/<label>.
3. Open the CF card editor: Commissioning > System data > Edit > basesys.ini. If the file does not exist, create it under /oem/sinumerik/ using New.
4. Paste the block above. Save with OK.
5. Reboot the NCU from Commissioning > NCK reset (po), or perform an HMI restart from Setup > HMI > Restart. A full NCU reboot (CF card boot) takes 60–90 seconds.

5.3 Editing via WinSCP or PuTTY

If a service PG already has SFTP access (via X120 after enabling SSH), the same edit can be performed with WinSCP 5.x:

1. Connect to sftp://192.168.214.1 using credentials manufact / manufacturer password (default: SUNRISE on legacy builds).
2. Navigate to /oem/sinumerik/. Right-click and Edit the file basesys.ini.
3. Append the [IBN] block above.
4. Save. The file is committed immediately; no reboot is strictly required for SFTP-side writes, but the firewall rules are re-read only on the next NCU reboot or on a manual firewall reload.

6. PG/PC Ethernet Adapter Configuration (DHCP)

The X127 port runs an internal DHCP server that issues leases in the 192.168.215.0/24 range. To receive a lease:

1. Open Control Panel > Network and Sharing Center > Change adapter settings on the PG.
2. Right-click the wired Ethernet adapter used for X127 and select Properties > Internet Protocol Version 4 (TCP/IPv4) > Properties.
3. Select Obtain an IP address automatically and Obtain DNS server address automatically. Click OK.
4. Disconnect and reconnect the patch cable to force a DHCP DISCOVERY. Wait 5–10 seconds.
5. Verify the lease: open Command Prompt and run ipconfig /all. The Ethernet adapter should report:

   
   Ethernet adapter Local Area Connection:
      Connection-specific DNS Suffix . :
      Link-local IPv6 Address . . . . . : fe80::xxxx
      IPv4 Address. . . . . . . . . . . : 192.168.215.x
      Subnet Mask . . . . . . . . . . . : 255.255.255.0
      Default Gateway . . . . . . . . . : 192.168.215.1
   

If the lease returns an APIPA address (169.254.x.x), the DHCP DISCOVERY packets are not reaching the NCU. Possible causes: bad cable, NIC power-saving (disable with powercfg -energy off), or X127 disabled in firmware.

7. STEP 7 / TIA Portal Access Address Configuration

Once the PG holds a valid lease and the firewall allows TCP/102, configure the online access address inside the engineering tool.

7.1 STEP 7 V5.5 (classic)

1. In the SIMATIC Manager project tree, select the program folder (for example S7-Programm > Sources).
2. From the menu bar choose PLC > Access Address...
3. If the dialog prompts Do you want to create a new access address? confirm with Yes.
4. Enter the address exactly as 192.168.214.1 for system-network X120 access, or 192.168.215.1 for direct X127 access. Note: STEP 7 V5.5 resolves the PLC through the project's PG/PC interface, which by default uses ISO transport. Ensure the PG/PC interface is set to TCP/IP (Auto) with the wired Ethernet adapter bound.
5. Click OK. The Accessible Nodes view should populate within 3–5 seconds with the NCU listed as NCU 730.3 PN.

7.2 TIA Portal V13–V18

1. Open the project and switch to the Project view.
2. Select the PLC device (for example PLC_1 [NCU 730.3 PN]).
3. In the device view, navigate to Properties > General > PROFINET interface > Ethernet addresses. Confirm the IP address matches the controller's IP on the subnet you are connected to (192.168.215.1 for X127).
4. Right-click the PLC device and choose Go online > Go online. In the dialog select PG/PC interface = Intel(R) Ethernet Connection ... TCP/IP and Subnet = Direct connection to PG/PC.
5. Click Start search. TIA Portal enumerates the subnet and the NCU appears as NCU 730.3 PN [00:0E:8C:xx:xx:xx].
6. Select the NCU and click Go online. The online status indicator turns green once the S7 connection is established.

8. Internal HMI Activation and IP Verification

If a separate PCU is not present (the NCU is the only HMI node), the internal HMI on the NCU must be activated to expose the X127/X120 commissioning menu and the System Network Center. The activation key sequence depends on the connected panel:

1. Press and hold the RECALL (^) key on the operator panel.
2. While holding RECALL, press the MENU SELECT key.
3. The internal HMI boots in approximately 30 seconds. A second desktop appears with the commissioning menu.
4. Open a shell (Operate Start > System > SINUMERIK > Shell) and run ifconfig eth1. The output should show:

   
   eth1      Link encap:Ethernet  HWaddr 00:0E:8C:xx:xx:xx
             inet addr:192.168.214.1  Bcast:192.168.214.255  Mask:255.255.255.0
   

5. Confirm X127 separately with ifconfig eth2:

   
   eth2      Link encap:Ethernet  HWaddr 00:0E:8C:xx:xx:xx
             inet addr:192.168.215.1  Bcast:192.168.215.255  Mask:255.255.255.0
   

If eth2 is absent or has no IPv4 address, X127 has been disabled in the BIOS or in the active Sinumerik boot configuration. Re-enable it from the NCU's boot loader menu (Select boot mode > Service mode) or by re-flashing the NCU firmware through the SIMATIC Automation Tool.

9. Alternative Connection Paths

When X127 is occupied or physically disabled, three alternative paths allow online access to the NCU from a PG.

For most field cases, the X120-via-switch route is the fastest fallback because it bypasses the basesys.ini firewall changes entirely.

10. Sinumerik Operate Remote Service Request Configuration

On the PCU50.5 side, the "Routing error" dialog appears when Operate tries to forward a remote service request from the system network to the IBN subnet. Two prerequisites must be in place:

1. The NCU basesys.ini contains EnableSysNetToIBNForwarding=1 (see Section 5).
2. The PCU's own routing table can reach 192.168.215.0/24. Verify with route print on the PCU (via remote desktop) and confirm a route exists through the X120 NIC.

If the PCU has a static IP on 192.168.214.x and no default gateway, add a static route:

route ADD 192.168.215.0 MASK 255.255.255.0 192.168.214.1 METRIC 1

After both sides are configured, retry the remote service request from Operate Diagnostics > Remote access > Request service. The dialog should complete within 5–10 seconds and show "Online" status against the NCU.

11. Verification Matrix and Field Acceptance Test

Use this matrix as the sign-off checklist after applying the procedure.

If the reboot-persistence test fails, the configuration is being read from the wrong basesys.ini path. Use WinSCP to verify which file the NCU actually reads at boot by inspecting /var/log/messages for the line Reading basesys.ini from /....

12. Common Pitfalls and Field Notes

• Static IP on the PG. Setting the PG to a manual address such as 192.168.215.2 works only if the NCU's DHCP server is disabled. If the lease already issued 192.168.215.2 to another device (for example a temporary HMI), a static configuration causes a duplicate-address conflict. Always prefer DHCP.
• Hyper-V / WSL virtual switches. Windows 10/11 often creates a Default Switch that grabs the Ethernet adapter. Disable it under Hyper-V Manager > Virtual Switch Manager or set the wired adapter's metric lower than the virtual adapter's metric.
• Wrong subnet gateway. Setting the gateway to 192.168.214.1 instead of 192.168.215.1 sends ICMP echo replies to the wrong interface and times out. Verify with route print.
• TCP/102 blocked by upstream proxy. Some plant firewalls strip RFC 1006 (ISO-on-TCP). When commissioning on the plant network (X130), open TCP/102 explicitly on the upstream switch ACL.
• Operate version mismatch. PCU50.5 running Operate 4.5 SP2 with NCU software 4.8 SP3 may show "Routing error" due to a known inter-version issue. Siemens bulletin recommends aligning both sides to the same service pack or upgrading the PCU to Operate 4.7.
• basesys.ini reset after CF restore. If the machine builder stored the IBN configuration only under /oem/sinumerik/ and the customer reimages the CF card from a backup, the change is lost. Document the IBN block in the machine's commissioning report.

13. Frequently Asked Questions