An IP address alone is not enough to determine which systems belong to the same network.

A system also needs a:

Netmask

Prefix Length

The netmask tells the operating system:

Which part of the IP address
represents the network.

IP Address + Netmask

Example:

192.168.1.10/24

The:

/24

is the netmask.

Equivalent notation:

255.255.255.0

What Does /24 Mean?

Example:

192.168.1.10/24

Therefore:

192.168.1.50

belongs to the same network.

But:

192.168.10.50

does not.

A Wider Netmask

Consider:

192.168.1.10/16

Equivalent:

255.255.0.0

Now the network portion becomes:

192.168

This means all of the following belong to the same network:

192.168.1.10
192.168.5.25
192.168.10.50
192.168.200.100

Visualized:

Network
192.168.0.0/16

├─ 192.168.1.10
├─ 192.168.5.25
├─ 192.168.10.50
└─ 192.168.200.100

Common Beginner Misconception

Many people assume:

192.168.1.0/24

and

192.168.10.0/24

must require:

Two NICs

This is not necessarily true.

The answer depends entirely on the netmask.

Example

Suppose a machine has:

192.168.1.10/16

Because the netmask is:

255.255.0.0

the operating system considers:

192.168.1.50

and

192.168.10.50

to be part of the same network.

Visualized:

192.168.0.0/16

        Switch
           │

    ┌──────┼──────┐
    │      │      │

192.168.1.10
192.168.1.50
192.168.10.50

Only one interface is required.

Why This Matters

When you see:

192.168.1.10

you should immediately ask:

What is the netmask?

Without the netmask, you cannot determine:

Network boundaries
Broadcast domain
Local hosts
Routing behavior

The IP address alone is only half of the information.

Operator Notes

For operators, netmasks define the size of a network.

These two addresses:

192.168.1.10/24
192.168.10.10/24

belong to different networks.

But these:

192.168.1.10/16
192.168.10.10/16

belong to the same network.

Whenever you enumerate a host, always collect:

IP Address
Netmask
Gateway
Routes

because together they reveal how the operating system sees the network around it.