Every device connected to a home network gets an address, rather like a house number in a housing complex. The router uses that address to know where data should go.
Most of the time this works without a thought. But when a printer suddenly isn't detected or a security camera disappears from its app, the root is often right here.
Two kinds of address
A public IP is assigned by your ISP to your whole household. From the internet's point of view, every device at home appears to use the same address. The router handles the sharing through a process called NAT.
A local IP applies only inside the house. The commonly used ranges:
| Range | Typically used by |
|---|---|
| 192.168.0.x – 192.168.1.x | Home routers |
| 10.0.0.x | Certain ISP routers, office networks |
| 172.16.x.x – 172.31.x.x | Corporate networks |
These addresses are called private because they aren't routed on the internet. Millions of homes
can use 192.168.1.10 at the same time without a problem, because each one only applies
inside its own house.
DHCP: the automatic address handler
DHCP is the service on the router that hands out addresses. The sequence goes like this:
- A new device connects and broadcasts a request: can anyone give me an address?
- The router replies, offering one address from the available range.
- The device accepts it and the router records the lease.
- The lease has a duration, usually 12 or 24 hours, renewed automatically while the device remains connected.
Because it's a lease, addresses can move. A phone switched off overnight may get a different address the next morning. For a phone that's fine. For a printer that's addressed by IP, it's a nuisance.
Why address conflicts happen
A conflict occurs when two devices use the same address. The symptoms are distinctive and confusing: the connection works briefly then drops, one device pushes the other off, or Windows shows an "IP address conflict" warning.
The three most common causes:
1. A static IP inside the DHCP range
Someone set a fixed address of 192.168.1.50 directly on a device, but the router is
still free to hand that address to another device. Sooner or later the two meet.
This is the most frequent cause, and the easiest to avoid.
2. Two routers both running DHCP
This often happens when someone adds a second router to extend coverage without turning off its DHCP. Now two parties are handing out addresses without knowing about each other.
The fix: turn off DHCP on the second router and connect it via a LAN port, not the WAN port. The second router becomes an ordinary access point. The full discussion is in the guide to mesh, repeaters, and access points.
3. A DHCP range that's too narrow
Some routers limit the range to 20 or 30 addresses. In a home with many smart devices, this can run out. Devices arriving later fail to get an address, or take one still recorded as belonging to another device.
A similar symptom with a different cause. A device that ends up with an address
like 169.254.x.x actually received no DHCP reply at all. That's the fallback address a
device uses when it gives up waiting. Check the cable, or whether DHCP on the router is actually
enabled.
DHCP reservation: the right way to fix an address
If a device needs an address that doesn't change, don't set it on the device. Use a reservation on the router.
How it works: you tell the router that the device with a particular MAC address always receives a particular IP address. The device still requests via DHCP as normal, and the router always answers with the same address.
Its advantages over a static IP set on the device:
- All the records live in one place, the router
- The router knows the address is taken, so it won't give it to anyone else
- Nothing needs changing on the device itself
The menu is usually called "Address Reservation", "DHCP Reservation", or "Static Lease". You simply pick the device from the list of currently connected clients.
Devices worth reserving
| Device | Reason |
|---|---|
| Network printer | Computers store its address when first installed |
| NAS or home server | Accessed by fixed address |
| Security cameras | The recorder looks for them by address |
| Extra access points | So their admin page is always in the same place |
| Games console | If you use port forwarding |
Checking your device's address
Windows. Open Command Prompt and type ipconfig. Look for the "IPv4
Address" and "Default Gateway" lines. The second is the router's address.
macOS. System Settings › Network › select the connection › Details. The IP and router addresses are on the TCP/IP tab.
Android. Settings › Network & internet › Wi-Fi › tap the active network. Some versions hide it behind an advanced menu.
iOS. Settings › Wi-Fi › the (i) icon beside the network name.
Organising the address range
If you want to be tidier, separate the DHCP range from the reservation range. An easy-to-remember split:
| Range | For |
|---|---|
| 192.168.1.1 | Router |
| 192.168.1.2 – 192.168.1.49 | Reservations: printer, NAS, cameras, access points |
| 192.168.1.50 – 192.168.1.250 | Free DHCP: phones, laptops, guests |
With this split, seeing a device's address immediately tells you what kind of device it is. Conflicts also become nearly impossible, because the two groups never touch.
For a home with five devices this is overkill. For a home with twenty devices, several of which need reaching from others, it saves a great deal of troubleshooting time later.
Frequently asked questions
What's the difference between a local IP and a public IP?
A local IP only applies inside your home network and can't be reached from the internet. A public IP is the address your ISP assigns to the whole household, from outside, all your devices appear to use that same address.
Why does my device's IP address keep changing?
Because DHCP leases addresses for a fixed period. If a device is switched off past the lease period, its address can be given to another device. For devices that need a fixed address, use DHCP reservation on the router.
Is a static IP better than a DHCP reservation?
A DHCP reservation is almost always better for a home. The address stays fixed, but the configuration is centralised on the router, so there's no risk of forgetting and causing a clash. A static IP on the device helps when it must keep its address even if the router is replaced.
Can adding devices run out of addresses?
The default range usually provides around 100–250 addresses, far more than a home needs. Running out only happens if the range was deliberately narrowed, or in a business with many visitors coming and going.
