Static IP Address or DHCP Reservation? How to Pick an IP That Won't Conflict

A NAS, a printer or a home automation hub is easier to live with when its address never changes. Your bookmarks, backups and integrations always find it. But pick the wrong address, and two devices end up fighting over it, with problems that come and go. In this video we'll choose a fixed address the safe way.

As always, this is DeviceShelf's demo network, a made-up home with forty-four devices.

There are two ways to give a device a fixed address. The first is a reservation in the router. The router keeps handing out addresses as usual, but it always gives this device's hardware address the same one. This Synology NAS works that way: reserved, D H C P.

The second way is a static address, typed into the device itself. The router isn't involved at all. This Raspberry Pi was set up like that. DeviceShelf shows the difference when your router is connected under Settings, Scanning, because the router reports how each device got its address.

Which is better? For most homes, the reservation. The router stays in charge of everything else, the gateway and the name servers, and you change it all in one place. A static address on the device is for the router itself, for switches and access points, and for devices that must work even when the router is down.

If you do set an address on the device itself, it needs more than the address. It also needs the subnet mask, the gateway and the name server. Copy them from the network the device is on, not from an old tutorial. The top of the Network view shows them for this network: subnet one nine two, one six eight, one, dot zero, slash twenty-four, mask two five five, two five five, two five five, zero, and the router at dot one as the gateway. Write down the old settings before you change anything, so you can go back.

The most important question is which addresses the router hands out by itself. That's the D H C P pool. Open the Network view and scroll to Addresses. DeviceShelf has worked out a range from the leases it has seen, here from dot thirty-one to dot one hundred and one. It says plainly that this is an estimate: the real pool is at least that wide.

The exact range is in your router's D H C P settings. Look for D H C P server, address pool or IP range. Here the router hands out dot twenty to dot two hundred, so we enter that.

And now DeviceShelf finds three devices with a hand-set address inside that range: the Proxmox server, the Docker host and the Raspberry Pi. They work today. But the router doesn't know about them, and one day it hands the same address to a phone. Then two devices answer on one address, and whichever answers first wins.

The fix is simple: move them out of the pool, or turn them into reservations. Reservations inside the pool are fine, by the way, and DeviceShelf doesn't list them. That's how a reservation is meant to work.

Say you want dot fifteen for a new device. It's outside the pool. Type it into the filter: nothing on the network uses it. That's a good sign, but not proof. A device that is switched off, asleep or behind a firewall doesn't answer either.

This doorbell is a good example. It sleeps between rings and doesn't answer the scan at all. It's only in the list because the router reports it. So also check the router's list of connected devices and its reservations, and keep a short note of the addresses you've handed out by hand.

If it does go wrong, DeviceShelf tells you here. Duplicate addresses lists every address that two machines answer at the same time, with both hardware addresses, so you know which two devices to look at.

To set up the reservation, Open router takes you to the router's web page. Look for D H C P reservation, static lease or address reservation, and pick the device from the list. Write down the old address first, and change one thing at a time. For a NAS that runs backups, do it when nothing is running.

Afterwards, check the whole path, not just the new address: the device answers, its web page opens, and the backup job or the app finds it. Under Settings, Alerts, you can let DeviceShelf tell you whenever a device changes its address, so you'll know if a reservation didn't take.

So: prefer a reservation in the router. If you set an address by hand, keep it outside the pool. Check the router's list as well as the scan before you use an address, and let DeviceShelf watch for duplicates and address changes.

More videos about your home network are on our channel. DeviceShelf runs on Mac, Windows and Linux, at deviceshelf dot app.