Configuring WinCC Redundant Communication to S7-400H with CP-1613

1. Overview: WinCC and S7-400H Redundant Communication

SIMATIC WinCC (TIA Portal / WinCC V7.x) supports fault-tolerant communication toward a SIMATIC S7-400H automation system over Industrial Ethernet. When a redundant S7-400H CPU pair (for example CPU 414-4H / CPU 417-4H) is the data source, WinCC can be configured so that an HMI channel keeps running even if one physical Ethernet path drops. The mechanism is the S7-REDCONNECT software package, which is implemented in the SIMATIC NET PC software stack on the engineering / operator station.

Unlike WinCC server redundancy (which mirrors two WinCC servers against each other on a terminal bus), S7 connection redundancy concerns the path between the WinCC station and the S7-400H CPUs. The user goal in this scenario is unambiguous:

• The PC station hosts one CP-1613 (SIMATIC NET Industrial Ethernet PCI card) and one standard Intel / IE General Ethernet adapter.
• Both adapters terminate in physically separate Ethernet networks that reach both H-CPUs of the S7-400H.
• If the UTP cable on the CP-1613 is unplugged, the WinCC runtime must continue reading/writing tags through the IE General card, and vice versa, with no restart of WinCC and no manual channel switch.

2. Hardware Requirements

The following hardware is required to build a fault-tolerant S7 connection between a WinCC station and a redundant S7-400H system.

3. Software and Licensing Requirements

Without the S7-REDCONNECT license, a standard S7 channel in WinCC establishes a single connection to a single CPU and does not perform automatic failover to a backup interface. Verify the license key in Start → SIMATIC → SIMATIC NET → Communication Settings → S7-REDCONNECT; the icon must be green.

4. Reference Architecture

The two physical networks are the foundation of the redundancy. Each network carries S7 traffic to both H-CPUs, and the SIMATIC NET PC stack on the WinCC station maintains parallel connections on each interface.

+-------------------------- PC station (WinCC) --------------------------+
|                                                                         |
|   CP-1613 (idx 0)                  IE General (idx 1)                  |
|        |                                  |                            |
+--------|----------------------------------|----------------------------+
         |                                  |
   +-----+-----+                       +-----+-----+
   | Switch A  |                       | Switch B  |
   | (PlantNW1)|                       | (PlantNW2)|
   +-----+-----+                       +-----+-----+
         |                                  |
   +-----+-----+                       +-----+-----+
   | CP 443-1  |                       | CP 443-1  |
   |  H-CPU 0  |                       |  H-CPU 1  |
   +-----------+                       +-----------+
   |           S7-400H (H-CPU 0, H-CPU 1, sync link)            |
   +-----------------------------------------------------------+

From the WinCC perspective, only one logical S7 connection is configured; the underlying S7-REDCONNECT driver transparently binds it to the two physical interfaces and the two H-CPUs. The H system presents a single virtual CPU address (or two physical rack/slot addresses) to the user program.

5. STEP 7 / NETPRO Configuration

All PC-station side configuration is performed in the STEP 7 project that contains the S7-400H station. The WinCC station appears as a SIMATIC PC station in NETPRO.

5.1 Insert the PC station

1. Open the STEP 7 project containing the S7-400H.
2. Insert a new SIMATIC PC Station from Insert → Station.
3. Open HW Config on the PC station and insert:
   • One CP-1613 from the catalog (PROFINET IO / Industrial Ethernet → CP-1613).
   • A second CP-1613 if you want dual CP-1613 redundancy.
   • Alternatively / additionally the IE General (from PC Internal → Industrial Ethernet), assigned to the onboard NIC.
4. For each Ethernet interface, open its properties, switch to the MAC Address tab and tick Set MAC address manually; the diagnostic tools will not be able to report the link otherwise.
5. Assign each interface a unique IP address in its own subnet (e.g. CP-1613 A: 192.168.1.10 / 24 in PlantNW1; CP-1613 B or IE General: 192.168.2.10 / 24 in PlantNW2).

5.2 Configure the Fault-Tolerant S7 Connection

1. Open NETPRO and select the PC station.
2. Right-click the row for the S7-400H → Insert New Connection.
3. In the connection wizard, choose S7 Connection Fault-Tolerant (not the plain S7 connection). The wizard will display the available H-CPUs of the S7-400H.
4. Select the connection partner: the S7-400H station; the partner endpoint is the H system itself, not an individual CPU - S7-REDCONNECT talks to whichever H-CPU is master.
5. On the local endpoint, select the first CP-1613 (or IE General) and tick Activate CP redundancy in the connection properties.
6. Add the second interface as the redundant partner in the same dialog.
7. Download the PC station configuration (PC Station → Configure → Station Configuration Editor on the PC) so that the SIMATIC NET runtime loads the fault-tolerant connection.

6. WinCC Channel Configuration

On the WinCC side, only one S7 channel is needed. The redundancy is invisible to the HMI project.

1. Open the WinCC Explorer on the PC station.
2. In Tag Management add a new driver: SIMATIC S7 PROTOCOL SUITE → TCP/IP (or ISO for pure ISO-on-TCP / ISO transport; either works with REDCONNECT, but TCP is the common choice on CP-1613 with a generic NIC as the partner).
3. Right-click TCP/IP → New Connection and create a single logical connection named, e.g. S7400H_FT.
4. In the connection properties enter the IP address of the S7-400H's virtual interface (the rack IP for PlantNW1, or the first H-CPU's CP 443-1 address). Do not create two connections - S7-REDCONNECT handles the redundant paths internally.
5. Verify the connection name matches the connection configured in NETPRO. WinCC loads the connection list from the Station Configuration Editor at start-up.

No additional configuration in WinCC is required for the failover. The driver monitors the S7-REDCONNECT state in the SIMATIC NET runtime; on link loss it switches the logical connection to the second path within a few hundred milliseconds (typical 200-500 ms, depending on keep-alive settings).

7. Verification and Failover Testing

Before going live, perform an end-to-end failover drill.

1. Start WinCC Runtime. Confirm the S7 channel shows Connected status and tags are updating.
2. In Communication Settings → S7-REDCONNECT, verify that both interfaces are listed as Active.
3. Pull the UTP cable on CP-1613 A. Expected behavior:
   • WinCC tags continue to update via the IE General / CP-1613 B interface.
   • WinCC does not show a connection-loss alarm (or it shows a transient "redundancy switch" event, not a permanent failure).
   • Time to recover: typically < 1 s for the user-visible tag value.
4. Reconnect the cable, then pull the UTP cable on the IE General / CP-1613 B. Confirm symmetric behavior.
5. Stop the master H-CPU (via PG / mode switch) and confirm WinCC continues reading from the standby H-CPU through the S7-400H redundancy mechanism (separate from CP redundancy but commonly tested together).

8. Diagnostics and Troubleshooting Matrix

9. Design Notes and Field-Proven Caveats

• Two physical networks, not one VLAN. A single broadcast domain with two interfaces in the same subnet does not give independent failure modes. Use two switches, two subnets, two IP ranges, and patch them through to the two plant networks that reach the H-CPUs.
• One logical connection in WinCC. Creating two parallel S7 channels (one per interface) breaks the redundancy model and will cause duplicate tag values and double write actions during the brief overlap of a failover.
• License and driver are coupled. S7-REDCONNECT is sold as a power pack on top of the SIMATIC NET PC Software. Without it, the S7 driver runs in single-path mode regardless of how many CPs are installed.
• MAC address reporting. Tick Set MAC address manually in the CP-1613 properties in HW Config. Otherwise the S7-REDCONNECT diagnostics cannot reliably identify the failing path.
• Switching time. Failover is not instantaneous; budget 200-500 ms of tag staleness. For closed-loop control requiring sub-100 ms response, this is not the right mechanism - move to PROFINET S2 system redundancy instead.
• Document the partner endpoints. The connection partner in NETPRO is the S7-400H station object, not an individual H-CPU. If you bind the connection to a specific CPU, you lose H-system redundancy.

10. Related Redundancy Topics (Not Covered by S7-REDCONNECT)

Three additional, distinct concepts are often confused with S7-REDCONNECT:

1. WinCC server redundancy (RT Professional) - two WinCC servers monitoring each other over a terminal bus. Documented in How Redundancy Works (RT Professional); this is a separate layer from S7-connection redundancy.
2. S7-400H system redundancy - the two H-CPUs themselves, the sync module, the redundant power supplies, the redundant CPs. Independent of how the PC station talks to them.
3. PROFINET S2 / R1 / R2 system redundancy - newer mechanism, primarily for S7-1500R/H, not S7-400H. Requires PROFINET devices, not Industrial Ethernet.

FAQ