What is a subnet?

A subnet is a logically separated part of an IP network, created using a subnet mask, that defines its own range of IP addresses.

Short and clear: a subnet is a "part of a network" that has its own network address, range of hosts, and broadcast address.

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#What "dividing a network into subnets" means

Initially there is one network. Using a mask, it can be split into several smaller networks: subnets.

Each subnet has:

• a network address
• host addresses
• a broadcast address
• its own mask (or prefix)

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#Example (IPv4)

There is a network:

192.168.1.0/24

If you split it into /26 subnets, you get:

• 192.168.1.0/26
• 192.168.1.64/26
• 192.168.1.128/26
• 192.168.1.192/26

Each of them is:

• a separate subnet
• a separate broadcast domain
• a separate range of IP addresses

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#Why subnets are needed

Subnets are used for:

#1. Reducing broadcast traffic

• broadcast is limited to the subnet
• the network works more stably and faster

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#2. Logically dividing the network

• different departments
• different network segments
• different access levels

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#3. Convenient routing

Routers operate:

• not on individual IPs
• but on subnets (network addresses + mask)

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#4. Saving IP addresses

• addresses are allocated more rationally
• there are no "empty" ranges

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#Important points for an interview

• a subnet is defined by an IP address + mask
• different subnets:
  • do not exchange data directly
  • require a router
• each subnet is a separate broadcast domain

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#In short, for an interview

A subnet is a logically separated part of an IP network, defined by a network address and a subnet mask, which has its own range of IP addresses and is used to divide a network and simplify routing.