How to Work Out the Right IP Range Before You Set a Static IP at Home

You set up a printer, a media server or a camera, and it works for a week. Then the router restarts, the device gets a different address, and every shortcut and port rule that pointed at the old address stops working. The fix is a fixed address, but most people pick that address first and work out the network afterwards. Work out the range first, and the static address almost picks itself.

This post follows that order: find what your network already uses, pick a private range, size the subnet, and only then choose an address outside the router's automatic pool.

Start with what your network already uses

Write down four values from a device that is already connected: its IP address, subnet mask, gateway and DNS servers. On most home networks the gateway is the router, often ending in .1, and the mask is 255.255.255.0, the same as a /24 network. Those values are your starting point, not numbers to invent.

Also find your router's DHCP range, the block it hands out automatically, usually shown under DHCP or LAN settings. A manual static address inside that pool can later be handed to another device, and then two devices share one address and both break. A fixed address belongs outside the pool, or inside it only as a reservation the router controls.

Pick a private range, and think about VPN clashes

Home networks use private addresses, which are not routed on the public internet. The three private blocks are 10.0.0.0 to 10.255.255.255, 172.16.0.0 to 172.31.255.255, and 192.168.0.0 to 192.168.255.255. Most home routers ship on 192.168.0.0 or 192.168.1.0, and for a simple home network that default is fine.

There is one reason to move away from the defaults. If you later connect to a work VPN and both networks use 192.168.1.0/24, the router cannot tell which network an address belongs to. A less common third number, such as 192.168.40.0/24, avoids that clash. Note that only 172.16 through 172.31 is private in the middle block.

Keep private and public addresses separate. Your LAN address is not your public internet address. To see the address the rest of the internet sees, use our What's My IP tool. Changing your LAN address does not change your public address.

Size the subnet from a device count, not a guess

A subnet mask, written as a slash number, says how many bits name the network and how many are left for devices. A /24 leaves 8 bits for devices, giving 256 addresses in total. Two are never assigned to a device: the first names the network itself and the last is the broadcast address. That leaves 254 usable addresses, for example 192.168.1.1 to 192.168.1.254 on 192.168.1.0/24.

Each extra bit in the prefix halves the usable space, so sizes come in fixed steps. A /25 gives 126 usable addresses, a /26 gives 62, a /27 gives 30, a /28 gives 14, and a /29 gives 6. There is no subnet that holds exactly 100 devices, so take the next size up and leave the spare addresses unused. That spare room is for the next camera or printer.

Count the devices that need a fixed address, add the ones you expect in the next year or two, then add headroom. For most homes a /24 is right even when only a few devices need fixed addresses, because it is the router default and it leaves room. Shrink the range only when deliberately splitting a network.

Work out the exact range with a calculator

Run your starting address and prefix through our Subnet Calculator. Enter the network address and prefix, or the dotted mask if that is how your router shows it. It returns the network address, broadcast address, mask, total and usable counts, and the first and last usable addresses.

For example, 192.168.1.0/24 gives a network address of 192.168.1.0, a broadcast address of 192.168.1.255, a mask of 255.255.255.0, and a usable range of 192.168.1.1 to 192.168.1.254. The router commonly sits at 192.168.1.1, so that address is already taken. The network and broadcast addresses must never be assigned to a device.

Choose a reservation first, a manual static address second

A DHCP reservation, sometimes called a static lease, is set on the router. You link a device's hardware address to one IP address, and the router always hands that device the same address. The device stays set to automatic, so it still receives its gateway and DNS settings from the router, and the router will not hand the reserved address to anyone else.

A manual static address is set on the device itself. You type in the IP address, mask, gateway and DNS servers by hand. That works, but the router does not know the address is taken unless you keep it out of the DHCP pool, and a typo breaks the device in a way that looks like a network fault.

Use a reservation whenever your router offers it, which most home routers do. Use a manual static address only when the device cannot use DHCP, when it must come up before DHCP is ready, or when a specific setup requires it. For a printer, network drive, camera system or home server, a reservation gives the same stable address with far less to maintain.

Checklist before you save anything

First, confirm the address is inside the usable range and is not the network or broadcast address. Second, confirm it is outside the DHCP pool, or exists as a reservation in the router. Third, confirm no other device already uses it, by checking the router's connected devices list. Fourth, confirm you copied the gateway and DNS servers exactly. A device with the right address but the wrong gateway reaches nothing beyond its own network.

After you apply the change, test from another device using the new address, then restart the device and test again. If the address survives a restart and the pool has not handed it to anything else, the job is done. If two devices claim the same address, remove the setting, find the duplicate in the router's device list, and start again from the checklist.

What to do first

Do not open a device's network settings yet. Open your router settings and write down your network address and mask, gateway, DHCP range, and how many devices need a fixed address. Run the address and mask through our Subnet Calculator and note the usable range. Pick fixed addresses outside the DHCP pool, set them as reservations where you can, write the layout down, and only then change a device.