In most homes the better arrangement is a reservation on the router rather than a fixed address on the machine, because the router then knows the address is taken. Either way the address must sit outside the range the router hands out automatically.
Two ways of achieving the same thing, and one of them is much harder to get wrong.
Reservation on the router: the better default
The router already hands out addresses. A reservation tells it to always give a particular device the same one, identified by that device’s hardware address.
The device itself is left on automatic and needs no configuration at all. The router knows the address is spoken for, so nothing else will be given it. And every reservation in the house is listed in one place, which is the property you will appreciate in three years when you have forgotten all of this.
The one requirement is that the router supports reservations, and most do.
A fixed address on the machine: when it is the right answer
Set on the enclosure itself, with four things to provide: the address, the subnet mask, the gateway — the router’s own address — and at least one name server.
Get any of the last three wrong and the machine will be reachable from inside the house and unable to reach anything outside it, which is a confusing state because the share still works.
This is the right approach when the router does not do reservations, when the machine must keep its address through a router being replaced, or in a network that has no automatic address handing at all.
Choosing the address
Look at the range the router hands out automatically. Almost every router lets you see it and change it, and it is typically a block within the private range in use on the network.
Put the fixed address outside that block, on the same subnet. Many people shrink the automatic range deliberately to leave a clear block at one end for fixed devices, which is a tidy habit.
Write it down. A list inside the cabinet door with a line per fixed device is worth more than any amount of remembering.
After the change
The enclosure will be at a new address, so anything referring to the old one has to be updated: mapped shares on machines, backup jobs, a printer configuration, port forwarding rules, and any bookmark to the management page.
Confirm it from a second machine rather than from the one you were working on, and confirm that the machine can still reach the outside as well as the inside.
Which other devices deserve the same treatment
Anything that other things go to rather than out from: a network enclosure, a printer, an access point or managed switch with a management page, a camera recorder, a home automation controller.
Everything else — phones, laptops, tablets, televisions — is better left automatic. A reservation list of five entries is useful; a list of forty is a second network to maintain.
The questions that come up before an order
What breaks if the address collides with the automatic range?
The router may hand the same address to something else, and then two devices answer to it. The symptoms are intermittent and confusing — a share that appears and disappears, a printer that works for one machine and not another — which is exactly why a reservation, made by the device doing the handing out, is the safer arrangement.
Do I still need this if I use the machine’s name instead of its address?
Name resolution on a home network is less reliable than people expect, and it is the first thing to become unreliable when something is wrong. A fixed address gives you something that works when discovery does not, and it is what any port forwarding rule or backup job will refer to anyway.
Last reviewed 10 September 2026