S7-1200 IP Address Permanent Change in TIA Portal V15.1

S7-1200 IP Address Permanent Change in TIA Portal V15.1

A common commissioning scenario on a new machine involves a CPU 1215 (or 1214 / 1212) configured with SINAMICS G120C frequency converters, where a service PC on site only has the TIA Portal V15.1 trial package installed. The technician can browse the PLC, see it under "Accessible devices", and even assign a new IP through Online & Diagnostics > Assign IP address, but the value reverts to the original after the next power cycle. The "Go online" and "Compile" toolbar options are grayed out in project view, and no project file exists on the site PC. This article explains the root cause, the three officially supported ways to make an IP change survive a power cycle, and the exact download / compile sequence required by TIA Portal V15.1 for a SIMATIC S7-1200 system.

1. Problem Description

Reproduction conditions:

• Hardware: SIMATIC S7-1200 CPU 1215 DC/DC/DC (6ES7215-1AG40-0XB0 or equivalent firmware V4.x), two SINAMICS G120C drives on PROFINET.
• Software: TIA Portal V15.1 trial, two DVD set installed, license still active.
• Topology: Direct Ethernet cable between the service PC and the CPU; PG/PC interface correctly bound to the Intel / Realtek NIC.
• Symptom 1: PLC is reachable under "Accessible nodes" with the original IP.
• Symptom 2: In the project tree, the device icon shows "Compile" or "Go offline" grayed out, indicating the project on disk is empty or the device configuration is not editable.
• Symptom 3: Online & Diagnostics > Functions > Assign IP address accepts a new value, but after power off / on the original IP is restored.
• Symptom 4: "Upload device as new station" returns "Upload not possible" because Startdrive / Startdrive HSP are missing on the service PC.

2. Root Cause Analysis

The S7-1200 stores the active IP address in two distinct locations:

When the PLC powers up, the startup routine (OB100) reads the project configuration from load memory and overwrites any temporary address that may have been set. The Online & Diagnostics > Assign IP address function is therefore a maintenance / commissioning tool, not a permanent configuration method. To make a new IP survive a power cycle, the value must be written into the project's hardware configuration and the project must be downloaded to the CPU.

3. Three Officially Supported IP Change Methods

Per the SIMATIC S7-1200 Programmable Controller system manual, IP addresses can be assigned to a CPU using the STEP 7 / TIA Portal programming package (Configuring an IP address for a CPU in your project). The three methods differ in persistence:

4. Prerequisites

Before attempting a permanent IP change, verify the following on the service PC:

1. TIA Portal V15.1 with a valid trial or full license. The trial DVD set includes the basic STEP 7 Professional option.
2. Startdrive V15.1 — required for the SINAMICS G120C. Without it, the device catalog will not show the G120C and the upload from CPU will fail.
3. Startdrive HSP (Hardware Support Package) V15.1 matching the G120C firmware. For a G120C with FW V4.7 (typical for units shipped 2018–2020) install HSP0183 Startdrive_G120C_V15.1 or newer. HSPs are downloaded from the Siemens Support entry 109770303.
4. S7-1200 HSP for V15.1 if the CPU is a newer 6ES7215-1AG40-0XB0 with FW V4.4 or higher. The HSP is installed via Options > Support Packages > Install.
5. PG/PC interface set to the physical Ethernet adapter used for the direct connection (S7ONLINE access point → Intel / Realtek NIC → TCP/IP).
6. Direct Ethernet cable (not crossed, modern NICs auto-MDIX) or via the plant switch with no other DHCP server on the segment.

5. Permanent IP Change — Step-by-Step (Project Available on PC)

Use this procedure when the original TIA Portal project is available on the service PC.

1. Open the project. In the project tree, expand the CPU (for example PLC_1 [CPU 1215 DC/DC/DC]).
2. Double-click Device configuration to open the device view.
3. Click the CPU's PROFINET interface (the green port label X1 P1 or X1 P2).
4. In the inspector window, switch to Properties > General > Ethernet addresses.
5. Clear "Set IP address using a different method" if it is selected, and enter the new values:
   IP address: 192.168.0.10
Subnet mask: 255.255.255.0
Router address: 192.168.0.1 (only if used)
6. For each G120C in the same project, repeat step 3–5. G120C addresses must be on the same subnet.
7. Right-click the CPU → Compile > Hardware and software (rebuild all). Wait for the green check.
8. Right-click the CPU → Download to device > All. In the download dialog, select "Search for compatible devices" rather than exact match, so TIA Portal will find the CPU by its current reachable IP and the new IP will be flashed.
9. In the Load preview dialog, check the box "Load IP address from device configuration". This is the option that writes the new IP to the CPU.
10. Confirm the stop-mode prompt, click Load, then Finish.
11. Power cycle the CPU. After restart it will come up with the new IP. Verify with Online & Diagnostics > Accessible devices.

6. Permanent IP Change — Step-by-Step (No Project Available on PC)

Use this procedure when the original project is not on the service PC, only the trial package is installed, and the on-site machine must be re-IPed without disturbing the running program. The principle is to recover the project from the CPU, change the IP, then download the modified project back.

1. Create a new empty project in TIA Portal V15.1.
2. From the project tree, double-click "Add new device" and add the same CPU type as detected (for example, CPU 1215 DC/DC/DC > 6ES7215-1AG40-0XB0 > V4.4). This sets up a valid hardware shell to receive the upload.
3. Select the CPU in the project tree. The Online toolbar icon is no longer grayed out because a real device is in the project.
4. From the menu, choose Online > Upload device as new station (HW and SW).
5. In the next dialog, choose "Search for compatible devices in the subnet". TIA Portal will list the CPU with its current IP and PROFINET name.
6. Select the CPU and confirm. The full project (ladder, FBs, DBs, device configuration) is reconstructed on the PC.
7. Open Device configuration > PROFINET interface > Ethernet addresses on the uploaded CPU. Enter the new IP, subnet, and router.
8. Repeat for the G120C devices if their IPs must change.
9. Compile > Hardware and software (rebuild all).
10. Right-click the CPU → Download to device > All. Use compatible devices as the search mode and tick "Load IP address from device configuration".
11. Power cycle the CPU to confirm the new IP is persistent.

If Upload device as new station returns an error that Startdrive or Startdrive HSP is missing, install both (see section 4) and repeat. The G120C topology cannot be reconstructed without Startdrive.

7. Handling the SINAMICS G120C on the Same Subnet

When the IP change also involves the G120C, follow the additional steps:

1. After the CPU IP change, open the device view of the G120C and assign it a unique IP in the same subnet. G120C default is 192.168.0.20; you can shift to 192.168.0.21 and 192.168.0.22.
2. Set the G120C PROFINET device name to match the project (for example g120c-1). The PROFINET name is what the CPU uses to identify the device on the network.
3. Compile the G120C device configuration separately if the project is partitioned, or compile the whole project.
4. Download the G120C configuration. TIA Portal will warn that the G120C will reset to factory defaults if the device name does not match. Confirm; the G120C will reboot and pick up the new IP and name.
5. For the second G120C, repeat with offset addresses.

8. Verification Procedure

After the download and power cycle, perform the following checks to confirm the IP change is permanent and the network is healthy:

1. Accessible devices — Open Online & Diagnostics > Accessible devices, search the subnet. The CPU must appear with the new IP. The old IP must not appear.
2. Ping test — From the Windows command line, run ping 192.168.0.10 -t. The CPU must respond to ICMP. The default S7-1200 firmware allows ICMP on the PROFINET interface.
3. Power-cycle test — Disconnect power, wait 10 seconds, re-apply power. Within 30 seconds, ping the new IP again. The reply must come back with the new IP, proving the configuration is in load memory, not RAM.
4. PROFINET name resolution — In Online & Diagnostics > Functions > Assign PROFINET device name, browse the network. The CPU and both G120Cs must appear with the correct names and reachable (green) state.
5. Online diagnosis — Right-click the CPU → Go online. The online view must show the CPU in RUN with no diagnostic buffer entries related to PROFINET station failure or IP conflict.
6. HMI / SCADA reachability — If a WinCC Runtime or HMI panel uses the CPU as a partner, trigger a connection test from the HMI. The connection must come up without a "partner not found" alarm.

9. Common Pitfalls and Workarounds

10. Field-Proven Notes

Some caveats that are not always obvious from the documentation:

• IP and PROFINET name are paired. The CPU uses the PROFINET name to find devices; the IP is then negotiated. If you change the IP but not the name, G120C IO may still come up. If you change the name but not the IP, IO will fail. Always download the entire hardware configuration, which updates both atomically.
• MRP / MRPD redundancy — if the network uses Media Redundancy Protocol, the IP change is propagated automatically, but the CPU must remain the MRP manager. Verify under Properties > PROFINET interface > Media redundancy.
• Time-of-day synchronization — NTP and S7 time-of-day rely on the IP for the source address. After an IP change, restart NTP synchronization on the HMI to re-establish the time server connection.
• Security — in TIA Portal V15.1 the default access level for the PROFINET interface is Full access (no protection). If the project has been hardened with a password and an access level of Read access or HMI access, the Online & Diagnostics > Assign IP function may be disabled until the CPU is unlocked with the project password.
• Trial license expiry — the trial license lasts 21 days from first activation. If the trial has expired, the project opens in a read-only state and downloads are blocked. Renew with a full license or re-create a fresh trial project.

11. Quick Reference — Parameter Mapping

12. FAQ