How do I change the IP address assigned to the PC without a router?

The point now is that I have a device which is not a router, but even if you connect the device to a laptop via RJ45 the laptop assigns its own IP address. When I change my IP address via the adapter options under Ethernet, I still have the old IP address I had before with DHCP. Would anyone have any idea how to change my IP address in my laptop without having to assign the device a static IP address. The device will only be set up via the laptop in the user interface of the device and will get a LAN connection afterwards.

The point now is that I have a device which is not a router, but even if you connect the device to a laptop via RJ45 the laptop assigns its own IP address.

So you have a device that is not a router and that has a DHCP server. Nu make no state secret out of it and say what that device is, maybe then you can help better.

When I change my IP address via the adapter options under Ethernet, I still have the old IP address I had before with DHCP

If that was really what I doubt, what would be wrong with your operating system. If you enter an IP address manually then the network adapter has exactly that IP address. Therefore, I do not understand how you come to the fact that you still have the DHCP assigned address. Unless you have entered the address assigned by DHCP manually again.

So, please tell us more. What is this ominous non-router device? And is the laptop connected via WLAN to a network at the same time? What is all connected where? Bissl more details.

I do not quite understand the question. You have only the choice zeische static or automatic IP address via DHCP. If your device has 192.168.178.1, for example, as would be the case with a Fritzbox, you can use the address 192.168.178.2 in the notebook, for example. After the configuration, you can reset your IP again. Or have I misunderstood that?

It makes more sense to ask how you solve the problem that you obviously have with a dynamic IP instead of asking how you could solve it. (Was hopefully understandable)

I now had no reason in a small home network why one needed a fixed IP. Apart from that, the IP of the next-higher "distributor" (ie router / switch) awarded. The static IP, which you change in the adapter settings, is therefore more of a kind of "request concert", which is taken into account by the router. If this is already taken (or other, depending on the router setting), then he simply ignores it.

Well it's a solar log. If that tells you something. The device is now set up via the user interface and then bound to LAN or Sim card to the Internet.