Most home networks just use whatever the router chose: 192.168.1.x for everything, a DHCP range nobody looked at. That works until you add a VPN, a second router, a NAS that must keep its address, or a smart plug you would rather not trust. A few minutes of planning avoids all of it, and the plan is the same every time.
Give each network 254 addresses (a /24) and use every one the same way. The router is always .1, network gear takes .2 to .9, devices that must keep their address live from .10 up to where DHCP starts, DHCP hands out the rest, and the last few addresses stay free. Fixed addresses sit below the DHCP range, so DHCP can never hand out an address that a printer or a server already uses.
.1 router (gateway)
.2 - .9 switches, access points
.10 - .99 printer, NAS, servers (fixed or reserved)
.100 - .250 DHCP: phones, laptops, everything else
.251 - .254 spareMost routers ship with 192.168.0.x or 192.168.1.x. Two networks with the same addresses cannot be joined, so a VPN back home stops working as soon as the hotel Wi-Fi uses the same range. Stay inside the private blocks (10.x, 172.16-31.x, 192.168.x) and choose numbers that are not the defaults: 192.168.10.x, 192.168.20.x and so on, where the third number tells you which network you are on.
One network is a fine start. Add more when there is something to protect or something you do not trust: a guest network for visitors, a network for smart-home gadgets that cannot be updated, one for cameras, one for servers. Devices on different networks cannot talk to each other unless you allow it, which keeps a compromised gadget away from your computers. Separate networks need a router or firewall with VLAN or guest-network support, and switches and access points that carry them.
home 192.168.10.0/24
iot 192.168.20.0/24
guest 192.168.30.0/24
servers 192.168.40.0/24Only one DHCP server may answer on a network, so turn off the one you are replacing. Use short leases where devices come and go (an hour for guests) and long ones where they stay (a day for the family, a week for cameras). If a device must always get the same address, give it a DHCP reservation in the router, or set it by hand inside the fixed range, never inside the pool.
Use home.arpa as the local domain: it is the name reserved for home networks (RFC 8375). Avoid .local, which collides with mDNS, and .lan, which is not reserved and may one day be sold.
Open the Home network IP plan generator
Not for a single network. You need them, or a router with guest and IoT network features, only to keep several networks apart.
Because almost every router and ISP box uses it. As soon as you connect to another network that also uses it, the two clash.
Bigger than the number of devices you will ever have at once. 150 addresses (.100 to .250) is plenty for a home, and it leaves 90 fixed addresses below it.
Use what it can: set the router address and DHCP range of the first network from the plan, and add the others when you get equipment that supports them.