S7-400H WinCC Redundancy: Selecting Softnet IE RNA vs RedConnect

Overview of S7-400H and WinCC Network Redundancy

SIMATIC S7-400H is a fault-tolerant PLC platform where two AS 410 / AS 400H CPUs run synchronized via fiber-optic redundancy links. When WinCC stations must visualize the H-system across a plant LAN, the question is no longer "can WinCC talk to S7-400H" but "how do you make that communication survive a single cable, switch, NIC, or PC failure without operator intervention."

Siemens offers two complementary software layers to achieve this on the PC side:

• SIMATIC NET SOFTNET-IE RNA – the layer that fuses two physical Ethernet adapters into one logical adapter using the PRP (Parallel Redundancy Protocol, IEC 62439-3).
• SIMATIC NET SOFTNET-IE S7 RedConnect – the layer that establishes and supervises high-availability S7 connections on top of that redundant path, including automatic switchover and reconnection after a fault.

The selection between these two products, the choice between software and hardware (SCALANCE X204RNA) redundancy nodes, and the licensing model are the three most common sources of error when engineering a S7-400H ↔ WinCC system. This reference consolidates the selection criteria, catalog numbers, supported CP modules, and configuration workflow for an S7-400H plant with V13 / V13 SP1 era WinCC stations.

Plant Network Topology Fundamentals

An S7-400H station contains two H-CPUs and typically two Industrial Ethernet CPs (e.g., CP 443-1) per CPU rack, or one CP per CPU when a SCALANCE X204RNA is used as the PRP redundancy box. From the network perspective there are two physical subnets (SubNet A and SubNet B). The WinCC station can connect to the H-system in three structural ways:

1. Two separate NICs, two separate IP addresses – classical approach using RedConnect high-availability S7 connections and S7-RECONN/S7-OPC for failover.
2. Two NICs bonded by RNA into one virtual adapter – the WinCC station sees only one IP but receives frames on both subnets simultaneously (PRP, zero-loss).
3. One NIC through a SCALANCE X204RNA – SCALANCE performs the PRP duplication in the network, PC sees a single LAN.

Methods (1) and (2) place the redundancy node in the PC. Method (3) places the redundancy node in the switch. The engineering, commissioning, and licensing implications differ in all three cases.

PRP and HSR terminology

PRP (Parallel Redundancy Protocol) duplicates each Ethernet frame on two physically isolated LANs and discards the duplicate at the receiver. Both frames are transmitted simultaneously, so there is zero switchover time on failure – the receiver simply keeps using the surviving frame stream. This is the protocol used by SCALANCE X204RNA and by SOFTNET-IE RNA. HSR (High-availability Seamless Redundancy) is a ring variant of the same IEC 62439-3 standard, used inside the S7-400H backplane network and not relevant to the PC connection.

SOFTNET-IE RNA versus SOFTNET-IE S7 RedConnect

Both products are part of the SIMATIC NET family and can co-exist on the same WinCC station, but they solve different problems.

Engineering rule of thumb: RedConnect alone gives you redundant S7 connections but the failure window is the S7-RECONN keep-alive cycle. RNA alone gives you lossless Layer-2 redundancy but the application still has only one S7 connection; if the S7 connection itself breaks the application has to recover it. The recommended S7-400H + WinCC engineering is to use both: RNA for the lossless LAN path, RedConnect on top for high-availability S7 connection supervision.

Recommended pairing on a WinCC station

• Physical PC (not VM) – 6GK1711-1EW13-0AA0 (RNA) + 6GK1704-0HB13-0AA0 (RedConnect, host-OS install acceptable for non-VM use but most plants install the VM SKU uniformly for licensing simplicity).
• WinCC running inside VMware/Hyper-V VM – the VM SKU of RedConnect (6GK1704-0HB13-0AA0) is mandatory, plus one RNA license per VM if RNA is also deployed in the VM (RNA cannot see host NICs in a VM; use two virtual NICs bridged to two host physical NICs).

SCALANCE X204RNA Integration

SCALANCE X204RNA (6GK5204-0BA00-2KB2 in current naming) is a managed Industrial Ethernet switch with four RJ45 ports and built-in PRP redundancy box function. It allows a device with a single Ethernet port (such as the on-board NIC of a WinCC IPC) to participate in a PRP network without installing RNA on the PC.

When SCALANCE X204RNA replaces PC-side RNA

The redundancy node moves from the PC to the network. The advantages and disadvantages are:

• Pro: Zero software footprint on the WinCC station – no RNA install, no driver, no virtual adapter. Simpler for OEM image deployment.
• Pro: Older WinCC versions without RNA support can still achieve Layer-2 redundancy.
• Con: Redundancy now starts at the SCALANCE, not at the PC. A failure of the SCALANCE itself is not protected.
• Con: Two SCALANCEs are required (one per SubNet A and SubNet B), and each must be paired with the corresponding PLC-side subnet.

Topology example with SCALANCE X204RNA

WinCC PC NIC 1 ─── Subnet A ─── SCALANCE X204RNA-A ──┐
WinCC PC NIC 2 ─── Subnet B ─── SCALANCE X204RNA-B ──┤
                                                        │ PRP trunk
                              CP 443-1 (CPU0) ─────────┤
                              CP 443-1 (CPU1) ─────────┘

Each SCALANCE X204RNA terminates one PRP subnet on the PC side and forwards over a single PRP trunk to the S7-400H rack. From the WinCC station's perspective there is still one IP address on its PC side, but the PC NIC count must be two (one per SCALANCE) unless the SCALANCE is configured as a DANP with a single uplink – which is not the supported pattern for S7-400H redundant connections.

Answer to the engineering questions

• Can SCALANCE X204RNA be used instead of SOFTNET-IE RNA? Yes – it performs the same Layer-2 PRP bonding function in hardware. The trade-off is that redundancy coverage no longer extends to the PC NIC.
• Can a single RJ45 on the motherboard be used? Only when redundancy starts inside SCALANCE X204RNA on the network side. A single PC NIC behind a SCALANCE is sufficient if the SCALANCE performs the PRP node function (DANP) and the partner side is also PRP-capable.

Communications Processor (CP) Selection

The CP modules installed in the WinCC station must be compatible with the chosen redundancy mechanism. Siemens explicitly excludes several HARDNET CPs from use with SOFTNET-IE RNA / RedConnect.

Two-CP configurations in the PC

When two CPs are installed in the WinCC station, the rule is:

• If both CPs are SOFTNET (e.g., two Intel NICs or CP 1626 in SOFTNET mode): install SOFTNET-IE RNA V13 to bond them, plus RedConnect VM V12 for S7 connection failover.
• If CPs are HARDNET: do not install RNA; install RedConnect VM V12 only and configure two distinct S7 connections in WinCC (one to CPU0, one to CPU1) with RedConnect supervision.
• Mixing one HARDNET + one SOFTNET: not supported by RNA driver; use RedConnect-only configuration.

Licensing Model

SOFTNET-IE RNA and SOFTNET-IE S7 RedConnect use a per-computer license model. The license is tied to the PC and is not per-CP, per-NIC, or per-subnet.

License files are stored in the standard Siemens license container (C:\ProgramData\Siemens\Automation\LicenseKey.bin on Windows 10/2016 or the equivalent AX NF ZZ directory on older OS). The Automation License Manager tool (almsrv.exe) must be running as a service for both products to start.

Configuration Procedure

The following step-by-step assumes a Windows 10 IoT Enterprise LTSC 2019 IPC running WinCC Professional V16, an S7-400H with two CP 443-1 EX30 modules, and the RNA + RedConnect combination.

Prerequisites

• SIMATIC NET DVD V13 + SP1 installed (mandatory – V12 only is not sufficient for the current RNA V13 driver).
• Two identical SOFTNET-compatible NICs installed and recognized by Windows (PCIe Intel i210 / i350 recommended).
• Both CPs visible in Device Manager without yellow bang.
• Automation License Manager (ALM) installed and shows both license keys as valid.
• WinCC project closed; no STEP 7 / TIA Portal connection to the AS during NIC rebind.

Step 1 – Install the SIMATIC NET stack

1. Mount the SIMATIC NET V13 SP1 DVD or run SIMATIC_NET_V13_SP1.exe.
2. Select Custom Install and enable: SIMATIC NET PC Software, SOFTNET-IE RNA, SOFTNET-IE S7 RedConnect, OPC Server.
3. Reboot when prompted. Confirm s7oiepn.dll and redpn.exe are registered (regsvr32 verification optional).

Step 2 – Configure the two NICs

1. Open Control Panel → Network and Sharing Center → Change Adapter Settings.
2. Rename the two NICs to SubNet_A and SubNet_B for clarity.
3. Assign static IPv4 addresses:
   • SubNet_A: 192.168.10.101 / 255.255.255.0, no gateway, no DNS
   • SubNet_B: 192.168.11.101 / 255.255.255.0, no gateway, no DNS
4. Disable IPv6 on both adapters (RNA V13 still uses IPv4 only in many firmware revisions).
5. Disable Windows firewall on these two adapters, or add inbound rules for TCP port 102 (S7) and UDP ports for SIMATIC NET discovery.

Step 3 – Bind RNA

1. Start SIMATIC NET Configuration → RNA Manager (Start menu → SIMATIC NET → Communication Settings → RNA).
2. Select Add PRP Interface.
3. Drag SubNet_A into the Adapter A slot, SubNet_B into Adapter B.
4. Assign the virtual adapter IP: 192.168.10.200 / 255.255.255.0 (this is the IP WinCC will use).
5. Click Apply, then Start RNA Service. The service SIMATIC NET RNA Service must be in state Running.
6. From a command prompt run ping 192.168.10.10 -t (CPU0 CP443-1 IP) and simultaneously pull the SubNet_A cable. Pings must continue with zero loss.

Step 4 – Configure RedConnect in STEP 7 / TIA Portal

1. Open the S7-400H station in STEP 7 V5.6 (or TIA V16 with S7-400H package).
2. In NetPro / Devices & Networks, insert an S7 Connection with type S7 Connection High Availability from the WinCC PC (logical partner) to the H-CPU pair.
3. Enter the Virtual RNA IP (192.168.10.200) as the partner endpoint.
4. Enable RedConnect on the connection; STEP 7 inserts a second logical S7 connection as standby automatically.
5. Compile and download to the H-CPU pair and to the PC station (via PC internal station or via S7PCT).

Step 5 – Verify in WinCC

1. Open the WinCC project in WinCC Explorer / TIA Portal.
2. In Tag Management → SIMATIC S7 PROTOCOL SUITE → Connections, the S7 connection name from Step 4 must appear with status icon green.
3. Right-click → Connection Status: verify RedConnect Status = Active and Active Path = LAN A initially.
4. Force a fault (disconnect LAN A cable). Status must switch to Active Path = LAN B within the configured timeout (default 3 s). Reconnect; status returns to LAN A after the configured recovery delay.

Commissioning Verification

A commissioned S7-400H ↔ WinCC redundant link must pass four scripted checks before plant handover.

Document the timestamp, tag value before/after, and any WinCC alarm raised during T2-T4. The acceptance report should attach the RNA log file (%ProgramData%\Siemens\Automation\RNA\rna.log) and the RedConnect log (%ProgramData%\Siemens\Automation\RedConnect\rc.log) covering the test window.

Troubleshooting Matrix

Edge Cases and Field-Proven Caveats

• Multiple VLANs on the same physical NIC: RNA does not support VLAN tagging in V13. Each RNA adapter must be on a single, untagged VLAN.
• Wireless or USB NICs: Not supported by RNA driver – only wired PCIe NICs with NDIS 6.x drivers.
• Hyper-V generation 2 VMs: The synthetic NIC is not always recognized; use the legacy network adapter for the two RNA-bound virtual NICs.
• Antivirus: Some endpoint security products intercept the raw Ethernet frames that RNA uses for duplicate detection. Add the RNA service executable (s7oiepns.exe) to the AV exclusion list.
• Switch recommendation: Use SCALANCE XC/XB/XR managed switches with PRP option enabled on the relevant ports. Unmanaged switches will work but eliminate the ability to diagnose SubNet-A vs SubNet-B via SNMP.
• Time synchronization: Both subnets must use the same PTP/NTP source to avoid timestamp drift between LAN-A and LAN-B frames, which can affect S7-OPC sequence numbers during failover.

Comparison: All Three Approaches Side by Side

Reference Standards and Official Documentation

Selection and parameter settings in this article are derived from the official Siemens Software Redundancy for SIMATIC S7 manual and the SIMATIC NET V13 + SP1 release notes. Always cross-check the WinCC / S7-400H manuals for the exact firmware revision in use at the plant.

• SIMATIC S7 Software Redundancy – Configuration Manual (Siemens Support, entry ID 1137637)
• IEC 62439-3 (PRP / HSR) – Clause 4 for PRP node and Clause 5 for HSR node behavior.
• SIMATIC NET V13 + SP1 product release notes – list of supported CP modules and unsupported HARDNET CPs.
• S7-400H – System Manual (Siemens), Section on S7-RECONN / high-availability S7 connections.
• SCALANCE X204RNA – Operating Instructions, PRP redundancy box mode description.