Problem Overview
In a multi-node EtherNet/IP network driven by RSLogix 5000 / Studio 5000 Logix Designer and RSLinx Classic, a remote CompactLogix L32E (1769-L32E) processor can appear in the RSWho tree with a yellow question mark and the label "unrecognized device" even though RSLinx correctly identifies the device family. The node is reachable at the IP layer (ping succeeds, Ethernet Devices driver browses it), but I/O configuration, MSG instructions, and tag browse all fail because the workstation cannot interpret the device's CIP identity object properly.
This symptom most often appears in mixed-firmware subnetworks where one vendor's panel was upgraded to a newer Logix firmware revision (for example, V19) while the supervising workstation still runs an older RSLogix 5000 V17.01. It is also triggered by out-of-date EDS libraries on the host after Rockwell ships device firmware changes.
Root Cause Analysis
The yellow question mark in RSLinx RSWho is generated when the workstation's EDS library does not contain a registered description that matches the device's CIP identity object. There are three primary triggers:
- EDS file version mismatch – The installed EDS describes an older revision of the ENBT/A Ethernet bridge or the 1769-L32E module than the firmware currently running on the hardware. RSLinx therefore cannot resolve the icon, vendor ID, or product code.
- Duplicate or mis-typed IP address – A device browsed at the wrong IP shows a yellow question mark with a red X. Verify the IP table before chasing EDS files.
- RSLinx Classic v2.58.00 SR4 or later – Rockwell changed RSWho icon resolution; devices that were previously recognized with generic icons may now show as unrecognized until EDS is registered.
Per Rockwell Knowledge Base Answer ID 501541, RSWho "unrecognized device" behavior with a yellow question mark is an expected result of the revised icon library shipped in RSLinx Classic v2.58.00 SR4. Per Answer ID 29685, a yellow question mark combined with a red X is almost always an IP address assignment error, not an EDS problem.
Affected Hardware and Firmware
| Component | Catalog | Symptom |
|---|---|---|
| CompactLogix Processor | 1769-L32E, 1769-L35E, 1768-L43 | Yellow ?, "unrecognized device" in RSWho |
| EtherNet/IP Bridge | 1756-ENBT, 1756-EN2T, 1756-EN3TR | Yellow ?, "unrecognized device" in RSWho |
| Stratix Switch | 1783-EMS, 1783-BMS, 1783-SRP | Yellow ? until EDS installed |
| Third-party CIP device | Various (ProSoft, Moxa, HMS Anybus) | Yellow ? until vendor EDS registered |
Diagnostic Procedure
-
Confirm physical/IP connectivity. Open a Command Prompt and execute
ping <target_IP>. Successful echo confirms Layer 3 reachability; it does NOT confirm CIP/EDS resolution. - Open RSLinx RSWho (Start → Programs → Rockwell Software → RSLinx → RSWho). Drill into the Ethernet Devices driver. Note whether the icon shows yellow? + red X (IP problem) or yellow? only (EDS problem).
- Read the device identity with CIP. Use Start → Programs → Rockwell Software → CIP Diagnostics or a third-party tool such as Studio 5000 Logix Designer → Who Active → Go Online. Record the Vendor ID, Product Code, Revision, and Serial Number returned by the device's Identity Object (Class 0x01, Instance 1, Attribute 1–7).
- Compare to the installed EDS library. In RSLinx, navigate to Help → About RSLinx → EDS Files (or run the EDS Hardware Installation Tool described below). Search the listed catalog number; if the device's revision is higher than any registered revision, EDS update is required.
Solution: Install or Update the EDS File
The fix is to register the matching EDS into the RSLinx EDS library. The recommended path is the EDS Hardware Installation Tool bundled with every RSLinx Classic install.
-
Download the current EDS bundle from the Rockwell Automation Product Compatibility and Download Center (PCDC) at compatibility.rockwellautomation.com. Use catalog filters 1769-L32E, 1756-ENBT, and any other device showing the yellow icon. The zip contains one or more
.edsfiles. - Launch the EDS Hardware Installation Tool: Start → Programs → Rockwell Software → RSLinx → Tools → EDS Hardware Installation Tool. Click Next on the welcome dialog.
- Register a directory of EDS files – select Add and point the wizard to the unzipped folder. The tool parses the CIP header and shows the registered devices in a tree.
- Select the target EDS entries and click Register. When registration completes, the wizard reports "Successfully Registered". Multiple EDS files for the same catalog at different revisions are all retained; RSLinx picks the highest matching revision.
- Close RSLinx completely (right-click the systray icon → Shutdown RSLinx). Re-launch RSLinx Classic, reopen RSWho, and re-browse the Ethernet driver. The yellow question mark should resolve to the correct module icon (typically a green/yellow PLC processor icon for the L32E).
C:\Users\<user>\AppData\Local\Rockwell Automation\RSLinx\Cache\* before re-opening. The cache stores resolved device descriptors and can mask a successful EDS install.Alternative: Manual EDS via Studio 5000
Logix Designer includes an EDS registration utility accessed through Tools → EDS Hardware Installation Tool. The behavior is identical to the RSLinx path. Use this method when RSLinx is not installed on the workstation (for example, on a development laptop used only for programming).
Verification Steps
- In RSWho, the yellow question mark is replaced by a standard module icon (green flag for healthy, yellow for faulted but recognized).
- From Studio 5000 / RSLogix 5000, open Who Active, navigate to the device, and click Go Online. The project should download and the controller should transition to Remote Run or Remote Program.
- From the Controller Properties → General tab, confirm the Type field shows 1769-L32E, the Revision matches the firmware, and the Serial Number matches the physical module.
- Send a CIP MSG from the local processor to a remote L32E and confirm a successful response (status word 0x0000 in the MSG tag).
Edge Cases and Field-Proven Caveats
- Version-coherent networks: When the entire subloop is on Logix V17 and the MCP is also on V17, EDS V17 is sufficient. Mismatched revisions between the MCP and subordinate panels almost always correlate with EDS problems on the older-firmware node.
- ENBT vs EN2T: A 1756-ENBT (10/100 Mbps) and a 1756-EN2T (1 Gbps) ship with different EDS catalog numbers. Installing only one will leave the other yellow.
-
DHCP and duplicate IPs: A device showing yellow? + red X with EDS already installed is almost always an IP conflict. Run
arp -aandpingfrom a Windows host to surface duplicate addresses. - RSLinx Gateway vs RSLinx Classic: The EDS library is shared, but the cache is per-install. Editing EDS in one product will not invalidate the other product's cache until the service is restarted.
- Multiple EDS revisions: Installing the V19 EDS on a V17 host does not damage V17 capability; Logix Designer still downgrades CIP messaging to the older revision. The reverse (V17 EDS on a V19 device) leaves the host unable to recognize the newer revision, which is the original failure mode in this scenario.
Troubleshooting Matrix
| Symptom | Most Likely Cause | Fix |
|---|---|---|
| Yellow ? + red X, all devices | Wrong IP in Ethernet Devices driver | Correct IP per Answer ID 29685 |
| Yellow ?, only newer-revision devices | Out-of-date EDS library | Install latest EDS via Hardware Installation Tool |
| Yellow ?, after RSLinx upgrade to v2.58 SR4+ | Icon library change, EDS registration lost | Re-register all EDS, clear RSLinx cache |
| Yellow ?, ENBT card only | 1756-ENBT EDS not registered | Install ENBT EDS bundle from PCDC |
| Yellow ?, intermittent | Switch spanning-tree flap or duplex mismatch | Check switch port counters, hard-code speed/duplex |
| Green icon, but Go Online fails | EDS OK, but RSLinx route table missing | Add device to RSWho → Configure Drivers → Ethernet Devices |
References (inline, official only)
Primary troubleshooting references used in this article: Rockwell Answer ID 29685 – RSLinx Classic: Troubleshooting Ethernet Drivers, Rockwell Answer ID 501541 – RSLinx Classic RSWho "Unrecognized device" error and yellow question mark, and the Rockwell Product Compatibility and Download Center for EDS file acquisition.
What does a yellow question mark in RSLinx RSWho mean on a CompactLogix L32E?
It means the workstation's EDS library does not contain a registered description matching the device's CIP identity revision. The hardware is reachable at the IP layer, but RSLinx cannot resolve the icon, vendor, or product code. Install the latest EDS file for the catalog via the EDS Hardware Installation Tool, then restart RSLinx.
Why does a yellow question mark appear together with a red X?
Per Rockwell Answer ID 29685, this combination is almost always caused by a wrong IP address in the Ethernet Devices driver configuration. Verify the IP table, correct the address, and refresh RSWho before updating any EDS files.
Will installing the V19 EDS on a V17 host break V17 communication?
No. RSLinx and Logix Designer retain the lower-revision EDS as a fallback. The V19 EDS is only used when the device reports revision 19 or higher. You can install future revisions without disturbing existing V17 I/O and MSG traffic.
Where do I download EDS files for the 1769-L32E and 1756-ENBT?
Use the Rockwell Automation Product Compatibility and Download Center at compatibility.rockwellautomation.com. Filter on catalog numbers 1769-L32E and 1756-ENBT, download the EDS zip, and register it with the EDS Hardware Installation Tool under RSLinx or Studio 5000.
How do I clear the RSLinx cache after updating EDS?
Close RSLinx completely (right-click the systray icon → Shutdown RSLinx), then delete the contents of C:\Users\<user>\AppData\Local\Rockwell Automation\RSLinx\Cache\. Relaunch RSLinx and re-browse the Ethernet driver. The cache otherwise retains stale device descriptors and the yellow icon will persist.