S7 REDCONNECT Configuration for WinCC PCS7 OS H-System Redundancy

S7 REDCONNECT Configuration for WinCC PCS7 OS H-System Redundancy

S7 REDCONNECT is the Siemens SIMATIC NET PC software license that establishes fault-tolerant S7 (S7 connection) communication between a WinCC/PCS 7 OS station and a fault-tolerant S7-400H automation system over Industrial Ethernet. When the active CP 1613 A2 or its network path fails, S7 REDCONNECT switches the application transparently to the standby CP 1613 A2 without operator interruption, with no loss of tags in the WinCC/PCS 7 OS, and without restart of the runtime.

This technical reference covers architecture, licensing, OS compatibility, NETPRO configuration steps, failover behavior, and the most common install/configuration errors (including the Windows 7 install failure frequently reported in field calls).

1. System Architecture and Redundancy Model

S7 REDCONNECT sits at the boundary between a PC-based HMI/SCADA station and a fault-tolerant S7-400H PLC. The chain of components is:

1. S7-400H AS — two redundant CPUs (typically CPU 412-4H, CPU 414-4H, or CPU 417-4H) with synchronized hot-standby operation, each owning a CP 443-1 Ethernet CP connected to two physically separated Industrial Ethernet segments.
2. PC station running WinCC or PCS 7 OS — equipped with two CP 1613 A2 PCIe (or PCI) cards. Each CP 1613 A2 is wired to one of the two Ethernet segments from the S7-400H (physically separated networks for redundancy).
3. SIMATIC NET PC software — the runtime that loads the S7-REDCONNECT protocol stack and binds it to the CP 1613 A2 instances declared in NETPRO.
4. S7-REDCONNECT license — the unlock that activates the fault-tolerant S7 connection feature inside SIMATIC NET.
5. WinCC or PCS 7 OS — consumes the redundant S7 connection through the OPC server (S7-OPC-SRV) or directly via the WinCC channel SIMATIC S7 PROTOCOL SUITE / TCP/IP.

The redundancy is on the connection level, not on a per-tag level: WinCC holds a single logical S7 connection. S7-REDCONNECT decides which physical CP 1613 A2 carries the connection and flips to the backup on failure.

1.1 Functional Principle of a Fault-Tolerant S7 Connection

A fault-tolerant S7 connection is built from two parallel sub-connections:

Only one sub-connection is active at any time. S7-REDCONNECT monitors:

• Keep-alive frames on the active sub-connection (default ~1 s poll, configurable in NETPRO).
• CP reachability at the S7 layer (S7 connection state: established / broken).
• Link state of the underlying Industrial Ethernet port.

If N consecutive polls fail (default 3 lost messages, tunable via Monitoring time and Number of lost messages allowed before switchover), REDCONNECT closes the failed sub-connection and opens the backup. The flip is transparent to WinCC; tags continue to update, and the historical archive sees no gap as long as the failover completes inside the configured window.

2. Licensing and Order Numbers

The original 2006 part (referenced in the field report) is:

Subsequent releases move the part number forward to match SIMATIC NET versions. Field engineers should expect a part number of the form 6GK1716-0HB64-3AAx where the suffix digit changes with each SIMATIC NET release (2008, 2010, 2012, 2014, V14, V15, V16, V17, V18, V19). Each release is licensed for use with the matching PCS 7 / WinCC version.

The license is delivered as a License Key (file) tied to the volume serial number or C/O/M SID of the PC, not to a single CP 1613 A2. If the hardware changes (new SSD, new motherboard), the license must be rehosted via the Automation License Manager (ALM) by importing the certificate of license transfer generated on the original PC.

3. Operating System and SIMATIC NET Compatibility

The 2006 release explicitly excludes 64-bit and modern Windows OS versions. The compatibility matrix in the SIMATIC NET PC Software Readme shows the following:

4. Prerequisites

Before opening NETPRO, verify the following on the PC station:

• SIMATIC NET PC software installed and licensed (the version that contains S7-REDCONNECT).
• Two CP 1613 A2 cards installed and recognized by the SIMATIC NET configuration console (each appears as an IE_General module under the PC station in STEP 7 / NETPRO).
• STEP 7 / NETPRO project is open, with the PC station and the S7-400H station loaded as objects in the same project.
• A 32-bit or 64-bit PC (per the release’s compatibility) with HW NIC configuration stable — do not reassign CP indices after configuring fault-tolerant connections.
• License key for S7-REDCONNECT installed in ALM and assigned to the PC station.
• Both Ethernet segments from the H-CP443-1 to the two CP 1613 A2 ports are pingable from the PC with a stable round-trip time below ~50 ms.
• User logged in with administrative rights for the Configuration Console and ALM.

5. NETPRO and WinCC Channel Configuration

Configuration is performed in two stages: the redundant S7 connection in NETPRO, then the binding in WinCC.

5.1 NETPRO: Inserting a Fault-Tolerant S7 Connection

1. Open the S7-400H AS station; open the Properties of the first CP 443-1 (in rack 0, slot 4 of CPU 0). Note the MAC/IP address and the S7 connection ID reserved for the H system.
2. Open the second CP 443-1 (rack 0, slot 4 of CPU 1, or equivalent). Note the matching S7 connection ID on the standby side.
3. On the PC station, expand the hardware list to show IE_General modules for both CP 1613 A2 instances. Each module must have a unique IP address in its assigned segment.
4. Right-click the first IE_General (CP 1613 A2 #1) → Insert New Connection → S7 connection Fault-tolerant.
5. In the wizard, set:
   • Partner (AS): select the S7-400H station.
   • Connection path A: CP 1613 A2 #1 ↔ CP 443-1 #1 of CPU 0.
   • Connection path B: CP 1613 A2 #2 ↔ CP 443-1 #2 of CPU 1.
   • Connection ID: numeric ID for WinCC/OPC (e.g., 1).
   • Local ID: numeric ID used by WinCC channel SIMATIC S7 PROTOCOL SUITE → TCP/IP.
6. Under Fault-tolerant Properties set:
   • Monitoring time (default 3 s) — the time allowed for keep-alive loss before failover.
   • Number of permitted lost messages (default 3).
   • H station backup time if a redundant S7-400H CPU is configured.
7. Compile and download the PC station to the target using PC Internal download (or via Target → Compile and Download Objects in SIMATIC Manager). The compiled PC station generates the .xdb file that the Configuration Console uses to load the S7-REDCONNECT runtime into the CP 1613 A2 firmware. The runtime is not active until this xdb is downloaded to the PC.
8. Repeat for each additional AS the OS station must talk to. Each AS requires its own fault-tolerant S7 connection.

5.2 WinCC / PCS 7 OS: Channel Binding

In WinCC Explorer (or PCS 7 OS project editor):

• Open Tag Management → SIMATIC S7 PROTOCOL SUITE → TCP/IP.
• Right-click TCP/IP → New Connection → enter the fault-tolerant S7 connection ID configured in NETPRO (e.g., 1). The connection name appears with a special icon denoting fault-tolerant binding.
• Add tags and DB addresses as usual. WinCC routes them through S7-REDCONNECT, which decides per packet which CP 1613 A2 to use.

For PCS 7 OS specifically, the OS server is added to the PCS 7 project via AS-OS Engineering; PCS 7 automatically generates the fault-tolerant connections during compilation if the OS and AS share the same S7-400H station and both CP 1613 A2 cards are present in the PC station xdb.

6. Failover Behavior, Timing, and Diagnostics

6.1 Typical Switchover Time

Total switchover time is typically 3–5 seconds with default parameters. Loss of update for slow-changing tags (e.g., analog process values at 2 s update) is usually 1–2 samples. The OS operator does not see a connection break; alarm logging continues, and the Connection status indicator in WinCC stays green.

6.2 Diagnostic Sources

Detailed failover events are written to:

• Windows Event Log → source Siemens S7-REDCONNECT.
• S7-DOS log file %PROGRAMDATA%\Siemens\Automation\S7-REDCONNECT\*.log.
• WinCC diagnosis file WinCC_SysLog.dbl (in the project \diagnose folder).

6.3 Live Status Check

To verify the live state of the redundant connection on the PC:

• Open Configuration Console → S7-REDCONNECT module → Status. It shows the active CP, the standby CP, last switchover time, and last switchover reason.
• Run S7DBEPA.exe (S7 DOS-Base) and select the PC station to view the Connections table.
• On the H system, use the H-CPU web server (https://<CPU-IP>/index.htm) and the diagnostic buffer to confirm that the partner CPU is in master/standby correctly.
• Use ping -t from the PC to each CP 443-1 IP to validate both network paths.

In the AS, the connection status of the fault-tolerant S7 connection is held in OB1 / OB70–OB72 variables that PCS 7 exposes for visualization. PCS 7 OS faceplates typically display the redundant S7 connection state via standard block icons from the PCS 7 Advanced Process Library.

7. Troubleshooting Matrix

8. Verification, Acceptance Test, and Migration from 2006 Release

8.1 Acceptance Test Procedure

1. With both Ethernet segments connected and both CPs active, confirm in WinCC that all configured tags are updating at expected cycle.
2. Disconnect the active Ethernet cable (CP 1613 A2 #1 side or CP 443-1 #1 side). Within 3–5 s, tags should resume updating on the backup path. WinCC should not show a connection loss.
3. Reconnect the failed cable. The S7-REDCONNECT module should not automatically switch back; the active path stays on CP #2 until that path fails. This is by design to avoid thrashing.
4. From the H system, power down the active CPU. S7-REDCONNECT should keep the connection open because the standby CPU takes over the S7 connection on the same CP. Verify that no WinCC event is logged as a connection break.
5. In the S7-REDCONNECT Status panel, confirm that Last switchover reason is populated with a meaningful code (e.g., "timeout," "link down").
6. Capture the log file %PROGRAMDATA%\Siemens\Automation\S7-REDCONNECT\*.log for the project documentation package.

8.2 Migration from S7-REDCONNECT 2006 to Current

If the project inherited from a 2006-era plant still uses 6GK1716-0HB64-3AA0 on a Windows XP PC, the typical migration sequence is:

1. Verify the target PCS 7 version (current support is PCS 7 V9.1 with Windows Server 2019/2022; see PCS 7 Release Notes).
2. Procure the matching S7-REDCONNECT release from Siemens (e.g., 6GK1716-0HB64-3AAx for the SIMATIC NET version that ships with that PCS 7 release).
3. Replace the OS server hardware. CP 1613 A2 is end-of-life; current redundant OS servers use the Intel PRO/1000 dual-port server NIC + SIMATIC NET soft-PC stack. The successor product is documented under Industrial Ethernet / SOFTNET-S7 REDCONNECT in the current SIMATIC NET release notes.
4. Rehost the license via ALM to the new volume serial using the certificate of license transfer process.
5. Recompile the PC station xdb on the new OS version; download and verify with the procedure in §8.1.

For the H system side, the CP 443-1 modules can normally be retained; firmware must match the PCS 7 / SIMATIC NET release (see SIMATIC NET S7-CPs for firmware updates).

9. Field-Proven Caveats and Engineering References

9.1 Caveats

• License is per PC, not per CP. Two OS server PCs = two S7-REDCONNECT licenses.
• Both CP 1613 A2 must be physically separated at the Ethernet layer (different switches, different VLANs or subnets). Bridging them with a single shared switch defeats the purpose of network redundancy.
• Do not run WinCC Explorer and S7-REDCONNECT Status dialog on the production operator console during failover tests; the open handle can delay the switch.
• H system CPU redundancy is independent of S7-REDCONNECT. The H system handles AS-level failover (CPU 0/1 hot-standby). S7-REDCONNECT handles CP and network failover. Both work together but solve different problems.
• Keep-alive time of 1 s × 3 messages is the published default but plant-specific tuning (5 s × 5 messages) is common in noisy industrial environments to avoid switchover on transient packet loss.
• Do not run S7-REDCONNECT and a standard S7 connection to the same AS in parallel — the standard connection will consume the S7 connection resources and may interfere with the fault-tolerant one. Use the fault-tolerant connection for the OS and keep separate standard connections only for engineering.

9.2 Engineering References

• SIMATIC S7-400H Fault-Tolerant Systems, System Manual
• SIMATIC PCS 7 Process Control System, OS Documentation
• SIMATIC NET CP 1613 A2 product page
• SIMATIC NET PC Software Readme / Compatibility
• S7-REDCONNECT Configuration in NETPRO Application Example
• SIMATIC PCS 7 Product Support

10. FAQ