Resolving LOGO! Soft Comfort IP Address Mismatch with LOGO! 8

1. Problem Overview

When engineers attempt to connect LOGO! Soft Comfort (LSC) to a physical LOGO! 8 Base Module (BM) over Ethernet, the most common blocking fault is an IP address mismatch. The PC running LSC and the LOGO! 8 device sit in different IP subnets, or the demo version of LSC is being used in an attempt to push a program to real hardware. Either of these conditions causes the LSC "Online" or "Transfer" operation to fail silently or return a "different IP address" prompt, and engineers often see no further explanation in the dialog.

This article consolidates the two distinct root causes (subnet configuration and license limitation) and provides a deterministic procedure for both. It assumes the reader has a working installation of LOGO! Soft Comfort V9.x on a Windows 10/11 PC, a LOGO! 8.3 (6ED1052-1xx08-0BAx) or comparable 8th-generation Base Module, and a standard Cat5e/Cat6 patch cable.

2. Understanding the LOGO! 8 Ethernet Architecture

The LOGO! 8 generation introduced a built-in 10/100 Mbit Ethernet interface on the Base Module. Every BM exposes one RJ45 port labeled LAN that supports three simultaneous services: LSC program transfer, the integrated web server, and Modbus TCP/UDP I/O expansion. Expansion modules do not carry an Ethernet port of their own; they communicate to the BM over the internal bus on the right side of the device.

2.1 Default IP Behavior of LOGO! 8.3

When the BM boots for the first time, it broadcasts a DHCP DISCOVER. If a DHCP server responds, the BM takes that address. If no response arrives within roughly 10 seconds, the BM self-assigns a link-local address in the 169.254.1.0 – 169.254.254.255 range. The actual address can be read from the BM's built-in display (navigate to Network → IP Address on the LOGO! TD or front display) or by scanning the subnet from a tool such as arp -a after pinging the broadcast address 169.254.255.255.

3. Root Cause 1 — IP Address Subnet Mismatch

The error message "the IP addresses are different" is the LSC connection dialog's way of reporting that the BM and the host PC cannot establish a TCP session because they are on different /24 subnets. This is purely a Layer-3 routing problem — there is no firewall or device fault to troubleshoot until the addressing is corrected.

3.1 Why This Happens

Three scenarios dominate field service reports:

1. PC on a corporate LAN (e.g., 10.20.30.0/24) with the LOGO! BM still sitting on its link-local 169.254.x.x address. The PC's route table has no path to 169.254.0.0/16, so the TCP SYN to port 13504 (LSC's default transfer port) is never delivered.
2. Static IP on the BM set to a different subnet (e.g., 192.168.1.10) but the PC stays on DHCP, where the DHCP server issues an address in 192.168.0.0/24. The two addresses are in different /24 subnets even though both are "192.168" class C.
3. Multiple network interfaces on the PC (Wi-Fi + Ethernet) cause LSC to bind to a NIC that has no route to the BM. The Windows route table determines which adapter LSC uses for the connection.

3.2 The Quick Diagnostic

Open a Windows command prompt on the engineering PC and run:

Locate the Ethernet adapter you intend to use. Note its IPv4 Address, Subnet Mask, and Default Gateway. Then run:

where <LOGO!_IP> is the address shown on the BM display. A "Destination host unreachable" or "Request timed out" confirms the subnet problem. A successful reply means the network is healthy and the fault lies elsewhere (Section 4 or 8).

4. Root Cause 2 — LOGO! Soft Comfort Demo License Restriction

The second and equally common cause of a failed transfer is a license limitation, not a network issue. The Siemens LOGO! software product page documents that LOGO! Soft Comfort ships in three license tiers:

When a Demo version user selects Tools → Transfer → PC → LOGO! the dialog opens, scans the local subnet, and lists any discovered LOGO! devices. Selecting the device and pressing OK produces the "IP addresses are different" or "Transfer not possible in Demo mode" warning, depending on the LSC build. Engineers sometimes interpret this message as a network error when it is actually a license guard.

5. Prerequisites

Before changing any network settings, confirm the following:

1. Licensed copy of LSC V9.0 or later installed (6ED1058-0BA08-0YA1 or current). The license key is delivered as an electronic Certificate of License (eCoL) and activated through the Siemens License Manager.
2. LOGO! 8.3 Base Module (or compatible 8th-generation BM) with firmware V1.82.x or higher. Earlier 8.0/8.1 firmware is supported but predates the secure HTTPS web server.
3. Direct Cat5e/Cat6 patch cable or a dedicated switch between the PC and the LOGO! BM. Avoid managed switches with port security or VLAN tagging during initial commissioning.
4. Windows administrator rights on the engineering PC to assign a static IP address and to allow LSC through Windows Defender Firewall.
5. Knowledge of the current static IP of the LOGO! BM (or readiness to use the on-board menu to discover it).

6. Step-by-Step — Assign a Compatible IP Address to the LOGO! 8

Choose one of two paths depending on whether the BM is already reachable.

6.1 Path A — Configure from the BM's On-Board Display

1. With the LOGO! powered, press ESC until the main menu appears.
2. Navigate to Network → IP Address using the ▲ and ▼ keys.
3. Select DHCP = Off.
4. Set IP Address to a value inside the PC's subnet. Example: if the PC will be 192.168.10.50, set the BM to 192.168.10.10 with subnet mask 255.255.255.0.
5. Confirm each octet with OK.
6. Navigate to Network → Gateway and set 0.0.0.0 unless the BM needs to cross a router.
7. Back at the main menu, the BM will restart its network stack; this takes approximately 5 seconds.

6.2 Path B — Configure via the LOGO! Web Server

1. Discover the BM's current IP using arp -a on a link-local subnet (169.254.0.0/16), or read it from the on-board display.
2. Open a browser and navigate to http://<BM-IP>. Log in with the admin password (default: LOGO for older FW, custom for newer FW).
3. Select the System → Network tab.
4. Disable DHCP and enter the static IP, subnet mask, and (if needed) gateway.
5. Click Apply. The BM will drop the connection and reappear at the new address within 10 seconds.

7. Step-by-Step — Configure the Engineering PC

1. Open Control Panel → Network and Sharing Center → Ethernet → Properties → Internet Protocol Version 4 → Properties.
2. Select Use the following IP address.
3. Enter an IP in the same /24 subnet as the LOGO! BM but a different host octet. Example:

IP address:     192.168.10.50
Subnet mask:     255.255.255.0
Default gateway: 192.168.10.1   (only if required)

4. Click OK and close the dialogs. Windows will send a gratuitous ARP and the NIC is ready.
5. From the command prompt, verify connectivity:

C:\> ping 192.168.10.10
Reply from 192.168.10.10: bytes=32 time=2ms TTL=64

6. If ping fails, temporarily disable the Windows Firewall and any third-party endpoint protection to rule out packet filtering.

8. Step-by-Step — Establish the LSC → LOGO! 8 Connection

1. Launch LOGO! Soft Comfort V9 in Full mode. Confirm by checking Help → About — the license row should read "Full License", not "Demo".
2. Open your project, or start a new one with File → New.
3. Select Tools → Transfer → PC → LOGO! (or press Ctrl+D).
4. The Select Target dialog scans the local subnet. The discovered BM appears with its IP, MAC, and firmware version.
5. If the BM is not listed, click Add and manually enter the IP address. This is necessary when the BM sits in a different /24 and the broadcast cannot reach it.
6. Select the BM and click OK. LSC negotiates the connection on TCP port 13504 and verifies the firmware compatibility.
7. A progress bar shows the upload; on success the dialog closes and the program runs on the BM.

9. Verification

Use the following checks to confirm the system is fully operational after the procedure above:

1. Online Test: in LSC, Tools → Online Test. Toggle a digital input on the BM. The corresponding input LED in LSC must change within 1 second.
2. Web Server: browse to http://<BM-IP>. The home page should show the current variable values, and the Diagnostics tab should report the BM firmware and IP.
3. Round-trip program transfer: download the project, perform a power cycle on the BM, and confirm the program survives (Set Parameter flag in the program properties is enabled by default for retentive tags).
4. Watchdog: in Tools → Options → Transfer, enable Verify after transfer. This adds an MD5 checksum check that catches partial writes.

10. Troubleshooting Matrix

11. Field-Proven Caveats

• Firmware drift: LSC V9.0 will refuse to transfer to a BM whose firmware is older than the minimum supported for that LSC build. The error text usually reads "Incompatible firmware version". Run LOGO! Web Update Tool on the BM, or open the project in a matching LSC version.
• Power-on race: if the BM is set to DHCP and the router takes a long time to reply, the BM spends up to 10 seconds at 0.0.0.0 before falling back to link-local. LSC will time out at this stage. Pre-assign a static IP to avoid the race.
• Watchdog on the web server: the integrated web server consumes roughly 2 MB of BM work memory when active. If the project already uses more than 200 function blocks, the web server may be auto-disabled at compile time.
• SD card lockout: if a password-protected SD card is inserted in the BM, the PC cannot perform a Read operation even with a full LSC license. Remove the card or clear the protection from the BM menu.

12. FAQ