How do addresses describe network boundaries?

The boundary problem

Addresses identify hosts. Prefixes group networks.

A device needs an address, but a router also needs to know which part of that address describes the network and which part describes the host. The prefix length marks that boundary.

In 192.168.10.24/24, the /24 prefix means the first 24 bits describe the network. The remaining bits identify a host inside it.

A subnet groups addresses that belong to the same local network.Devices in the same subnet can usually communicate directly. Traffic for another subnet needs a router or another Layer 3 boundary.

Build the model

Three useful ideas

01

Address

Identifies an interface or destination, such as 192.168.10.24.

02

Prefix

Marks how many leading bits describe the network, such as /24.

03

Subnet

Defines an address range and the boundary for traffic within that subnet.

04

IPv6

IPv6 uses a much larger address space. A /64 prefix is common for IPv6 subnets.

Mini experiment

Place the address

Choose a prefix to see the size of its IPv4 address range and check whether two example addresses are in the same subnet.

PREFIX192.168.10.0/24

ADDRESS COUNTIPv4 address count: 256

RANGE192.168.10.0 - 192.168.10.255

EXAMPLE CHECK192.168.10.24 and 192.168.10.25 share this subnet

The /24 prefix defines this IPv4 range.

Knowledge check

Test your subnet model

Answer five questions. The answer order changes each time.

0 / 5