How to Set a Static IP on an EtherNet/IP Device with BOOTP or DHCP
A fresh EtherNet/IP adapter or drive out of the box usually has no usable IP and expects a BOOTP or DHCP server to hand it one by MAC address. Getting it a permanent address is a two-part job that people routinely half-finish: assign the IP, then disable the client so the device keeps that address after a power cycle instead of going hunting for a server again. This page walks the sequence for a technician staging a device, and explains why leaving the BOOTP client enabled is the mistake that comes back as a device that vanishes on the next reboot.
Set Static IP with BOOTP/DHCP in one line: To set a static IP on an EtherNet/IP device with BOOTP or DHCP, connect the device on an isolated network with a BOOTP/DHCP tool running, capture the request from the device's MAC address printed on its label, assign the target IP, subnet mask, and gateway, then disable the BOOTP/DHCP client on the device so the address becomes static. If you skip disabling the client, the device forgets the address at the next power cycle and waits for a server again. Verify by rebooting and confirming it keeps the IP.
Capture the Device by Its MAC Address
Work on an isolated network, not the live plant subnet, because a device with no address is about to broadcast for one and you do not want it colliding with production or grabbing a lease you did not intend. Put a laptop running the BOOTP or DHCP server tool and the target device on the same isolated switch or a direct cable. A device shipped expecting BOOTP or DHCP broadcasts a request at power-up containing its hardware MAC address, and the tool lists that request as it arrives.
The MAC address is your unambiguous handle on the right device, and it is printed on the device's label, so match the MAC in the tool's request list to the MAC on the label of the device in your hand. This matters when several devices are staged at once, because they all broadcast and the list fills with requests; the label is how you know which line belongs to the drive you mean to address. Assigning an IP to the wrong MAC is how the wrong device ends up at the right address, which becomes a duplicate later, the exact fault dealt with in fixing a duplicate IP address on a machine network.
Enter the target IP, subnet mask, and default gateway from the machine's IP schedule and assign them to that MAC. The device takes the address immediately and becomes reachable, and you can confirm by pinging it or opening its diagnostic web page. At this point the device has the correct address, but it does not yet own it permanently, which is the half of the job that is easy to walk away from.
Disable the Client So the Address Sticks
The step that makes the address permanent is disabling the BOOTP or DHCP client on the device. While the client is enabled, the device treats its address as a lease it must renew and will broadcast for a server again at the next power-up, so if the server is not there it comes up with no address and disappears from the network. Disabling the client tells the device to stop asking and keep the address you gave it as a static configuration held in nonvolatile memory. Most vendor tools offer a disable-client action once the device has an address, and some devices let you disable it from the device's own web page.
Prove it before you call the device done: power-cycle it and confirm it comes back at the same IP with no BOOTP or DHCP server present. This is the only test that actually verifies the address is static, because a device that still has an active client can look perfectly reachable right up until the reboot that reveals the client was never disabled. A device that returns at its address on a bare network, with nothing offering a lease, has genuinely kept it.
Where a device is meant to receive its address dynamically by design rather than statically, leave the client enabled but pin the assignment in the server so the device always gets the same address. Binding the MAC to a fixed IP reservation in the DHCP server gives you dynamic assignment with deterministic addresses, which is the reservation discipline that also prevents duplicates. The choice is deliberate: static-plus-disabled-client for devices that must survive a dead server, or reservation-bound DHCP for a managed dynamic scheme, but never an enabled client pointing at a server that may not be there.
Frequently Asked Questions
Why does my EtherNet/IP device lose its IP after a reboot?
Because its BOOTP or DHCP client is still enabled. With the client active, the device treats the address as a lease and broadcasts for a server again at power-up, so if no server answers it comes up with no address and vanishes from the network. Assigning the IP is only half the job; you must also disable the client so the device keeps the address as a static configuration in nonvolatile memory.
How do I know which BOOTP request is my device?
Match the MAC address. A device expecting BOOTP or DHCP broadcasts a request containing its hardware MAC at power-up, and that MAC is printed on the device's label. When several devices are staged together the tool's request list fills up, so the label is how you identify the right line. Assigning an address to the wrong MAC puts the wrong device at that IP and creates a duplicate later.
Should I use a static IP or a DHCP reservation for a field device?
Use a disabled client with a static address for devices that must survive a missing or failed server, since they keep their IP regardless. Use a DHCP reservation, binding the device MAC to a fixed address in the server, when you want centrally managed dynamic assignment with deterministic addresses. Avoid the middle case of an enabled client pointing at a server that may not always be present, which is how devices disappear on reboot.
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