After you write the intended address and disable BOOTP/DHCP, the adapter can return from a power cycle on the same static IP without the temporary laptop server. If it only works while that server is present, you assigned a lease; you did not finish static commissioning.
Start with the panel symptom
The replacement 1794-AENT powers up, but the controller cannot reach its remote I/O. A temporary DHCP server can place the adapter on the plant subnet, and the web interface then shows the expected network settings. Remove the server or cycle power, however, and the address may disappear because the adapter is still configured to request an address dynamically.
| Symptom | Most likely cause |
|---|---|
| The adapter appears only while the laptop DHCP server is running |
BOOTP/DHCP remains enabled; the displayed address is a dynamic assignment. |
| The web page displays network data but provides no edit controls | The embedded page is diagnostic and read-only on this adapter. |
| The adapter becomes unreachable immediately after you write the new IP | Your laptop is still on the temporary subnet, the production controller claimed the adapter, or the intended address conflicts with another device. |
| The intended address works until a power cycle | The address was assigned, but dynamic address acquisition was not disabled. |
| The adapter returns after power-up on the same address without a DHCP server | The static configuration was stored successfully. |
Start here: determine whether you have only an address or a stored static configuration. Repeatedly rewriting the same DHCP reservation does not correct the configuration mode.
Read the catalog label before choosing instructions
Check the catalog number printed on the installed adapter. The installation identifies a 1794-AENT, while one commissioning instruction associated with the case specifically names 1794-AENTR. Treat those as different catalog identifiers and select the matching product instructions in the commissioning software or installation manual.
This check decides how you interpret restart prompts and hardware-specific behavior. Do not apply an 1794-AENTR-specific prompt silently to a unit whose label reads 1794-AENT. For either device, the decisive field test remains the same: disconnect the temporary address service, cycle power, and confirm that the adapter returns on the intended IP.
Also record the approved static IP address and subnet mask from the existing network plan. The segment already contains roughly a dozen statically addressed controllers, so check the address inventory and test for an existing responder before assigning the replacement. An IP conflict can imitate an adapter or controller fault.
Isolate the adapter before changing its address
Connect the replacement adapter directly to the commissioning laptop or place both on an isolated network containing no other devices. This is the first physical check. Do not commission it while attached to the active control segment unless the control system has already been placed in a state that prevents it from connecting to the replacement.
Isolation removes three common failure paths:
- A second DHCP or BOOTP service cannot answer first.
- An unintended duplicate address cannot disrupt a running device.
- The production controller cannot establish a connection immediately after the address changes and interfere with the remaining commissioning steps.
Configure the laptop interface so it can communicate on the subnet you will use for the assignment. Disconnect or disable unrelated network paths that could change route selection. If the laptop cannot reach the adapter after the write, inspect the laptop address, mask, route, and link state before rewriting the module.
The address-selection thumbwheels do not solve this installation because the required plant address is outside the useful default 192.168.1.x case described for the adapter. Use them only to place the unit into the address-acquisition mode required by the documented commissioning method; do not try to encode an unsupported plant address with them.
Determine whether BOOTP or DHCP is still active
Run the Rockwell BOOTP-DHCP utility or the EtherNet/IP Address Commissioning Tool and watch for the adapter request. Identify the correct device before writing anything. On an isolated link, the newly powered adapter should be the only uncommissioned requester, which removes ambiguity.
If the adapter requests an address after every restart, BOOTP/DHCP is active. If it returns on the intended address without receiving a reply from the laptop, the static configuration is active. Seeing the desired IP in the web diagnostics proves only the current network state; it does not prove that the startup mode is static.
RSLinx can set a static address when the module already has a reachable temporary IP, but it is not required for this one-off task. Installing a full programming environment also wastes time when the free commissioning utility can perform address assignment and disable dynamic acquisition. The missing capability is the industrial commissioning operation, not ordinary DHCP service.
Write the intended network settings
Assign only values approved for the segmented control network. At minimum, record the intended IP address and subnet mask. If the design requires routed communication, take the gateway value from the network plan rather than copying one from the laptop.
- Disconnect the adapter and laptop from the production segment.
- Connect the laptop directly to the adapter and power the adapter.
- Open the BOOTP-DHCP utility or EtherNet/IP Address Commissioning Tool.
- Wait for the adapter to appear and identify the correct request.
- Write the approved IP address and subnet mask. Enter a gateway only when the network design calls for one.
- Move the laptop interface to the assigned subnet if it is not already there.
- Confirm that the adapter responds at the new address and that its diagnostic page reports the intended values.
If communication stops immediately after step five, that can be the expected result of moving the adapter to another subnet. Change the laptop address before concluding that the write failed. If both endpoints are on the same subnet and communication still fails, check the link indicators, address conflict, mask, and local host firewall.
Disable BOOTP and DHCP before disconnecting
This is the resolving branch. In the BOOTP-DHCP utility, select the assigned adapter entry in the lower portion of the application and issue the command that disables BOOTP/DHCP. In the EtherNet/IP Address Commissioning Tool, set the adapter to static rather than leaving dynamic address acquisition selected.
Do this while the adapter remains isolated and reachable. If you reconnect it to the production network immediately after writing the IP, the controller may connect before you complete the disable operation. Without programming software to inhibit that connection, direct laptop-to-adapter commissioning is the cleaner path.
Do not confuse these two operations:
- Assign address: gives the adapter its current IP, mask, and any required routing value.
-
Disable
BOOTP/DHCP: tells the adapter to retain and use its configured address instead of requesting another assignment at startup.
A successful DHCP reply performs only the first operation. Leaving the temporary laptop server on site would hide the incomplete configuration rather than fix it.
Power-cycle and verify the stored address
Remove the temporary DHCP or BOOTP service before testing. The EtherNet/IP Address Commissioning Tool guidance in the case calls for a power cycle on a 1794-AENTR before its changes take effect. For a 1794-AENT, follow the matching tool prompt and product instructions, then use the same power-cycle test to prove persistence.
- Close or stop the laptop DHCP/BOOTP service.
- Record the adapter's displayed IP address and configuration mode.
- Remove power from the adapter, then restore it according to the equipment procedure.
- Wait for the adapter to complete startup.
- From a laptop on the intended subnet, test reachability at the assigned address.
- Open the read-only diagnostic page and compare the reported IP address and mask with the approved values.
- Confirm that the commissioning utility does not show a new address request from the adapter.
- Reconnect the adapter to the plant segment and confirm that the controller establishes its normal I/O connection.
The test passes only when the adapter returns at the same address without help from the temporary server. A successful browser connection before the restart is not acceptance evidence.
Reject fixes that do not address the startup mode
Do not spend time looking for an edit button in the embedded web page. On the installed unit, that page exposes diagnostics and network configuration for viewing, not editing.
Do not treat an ordinary DHCP reservation as permanent adapter commissioning. It still depends on a server being present and reachable after every startup. That dependency contradicts a segment designed around static addresses with no resident DHCP or BOOTP service.
Do not install RSLinx or a full controller programming package solely to finish this assignment when the commissioning utility is available. Those tools can be useful when you must browse a larger control system or inhibit a module, but they do not replace the final BOOTP/DHCP disable step.
Do not return the adapter to the production network until you have tested persistence on the isolated link. If the address assignment works but the disable command repeatedly fails, capture the catalog number, tool name, displayed configuration mode, network values, and status indications before escalating.
FAQ
Why does my 1794-AENT lose its IP address after a power cycle?
The address was assigned while BOOTP/DHCP remained enabled. Reassign the approved network values, issue the utility command that disables dynamic acquisition, and repeat the power-cycle test with the temporary server stopped.
Why does the 1794-AENT web page show the IP but not let me change it?
The embedded page on this installation is a read-only diagnostic interface. Use the Rockwell BOOTP-DHCP utility, the EtherNet/IP Address Commissioning Tool, or a compatible commissioning path instead.
Why does the adapter disappear immediately after I assign its static IP?
The adapter may have moved to a subnet that your laptop cannot reach. Put the laptop on the assigned subnet, then check the mask, physical link, local firewall, and duplicate-address status before writing the configuration again.
Why does a DHCP-assigned address work but still fail the static-IP test?
DHCP proves that the adapter can communicate and accept a current address; it does not prove that dynamic acquisition is disabled. Stop the server and power-cycle the adapter to test whether the address was stored for static startup.
When should I stop troubleshooting and contact Rockwell Automation support?
Stop when the correct catalog-specific commissioning utility can discover the isolated adapter but cannot write the address or disable BOOTP/DHCP, or when status indications report a persistent hardware condition after a power cycle. Give official support the exact catalog label, utility name, displayed status, assigned IP and mask, and the result of the server-free restart test; do not reconnect an unresolved duplicate or dynamically addressed adapter to the production segment.