IPv4 Subnetting Explained Step-by-Step

Nerd Cafe | نرد کافه

1. What is IPv4?

IPv4 address = 32 bits = 4 octets

Example:

192.168.10.25

Each octet:

192 . 168 . 10 . 25

Binary form:

11000000.10101000.00001010.00011001

IPv4 consists of two parts:

• Network portion → identifies the network

• Host portion → identifies devices

2. What is a Subnet Mask?

Subnet mask tells:

Which part = network Which part = host

Example:

255.255.255.0

Binary:

11111111.11111111.11111111.00000000

Meaning:

• First 24 bits → Network

• Last 8 bits → Hosts

CIDR notation:

/24

3. Important Values You Must Calculate

From IP + Subnet Mask you find:

• Network IP

• Broadcast IP

• First IP

• Last IP

• Number of hosts

4. Practical Example

Given:

IP Address = 192.168.10.25
Subnet Mask = 255.255.255.0
CIDR = /24

Step 1 — Find Network IP

Formula:

IP AND Subnet Mask

Binary:

IP:

192.168.10.25
11000000.10101000.00001010.00011001

Mask:

255.255.255.0
11111111.11111111.11111111.00000000

Result:

11000000.10101000.00001010.00000000

Decimal:

192.168.10.0

✅ Network IP = 192.168.10.0

Step 2 — Find Broadcast IP

Broadcast IP =

All host bits = 1

Host bits = last 8 bits

Binary:

11111111

Broadcast:

192.168.10.255

✅ Broadcast IP = 192.168.10.255

Step 3 — First Usable IP

Formula:

Network IP + 1

192.168.10.0 + 1

Result:

192.168.10.1

✅ First IP = 192.168.10.1

Step 4 — Last Usable IP

Formula:

Broadcast IP − 1

192.168.10.255 − 1

Result:

192.168.10.254

✅ Last IP = 192.168.10.254

Step 5 — Number of Available IPs

Formula:

2^(host bits) − 2

Host bits:

32 − 24 = 8

Calculation:

(2^8) − 2
= 256 − 2
= 254

✅ Available IPs = 254

Final Results Table

Item	Value
IP Address	192.168.10.25
Subnet Mask	255.255.255.0
CIDR	/24
Network IP	192.168.10.0
Broadcast IP	192.168.10.255
First IP	192.168.10.1
Last IP	192.168.10.254
Hosts	254

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Keywords

IPv4, subnetting, IP addressing, network address, subnet mask, CIDR notation, broadcast address, host address, first usable IP, last usable IP, available hosts, binary subnetting, IP calculation, network engineering, TCP/IP, IP ranges, subnet calculator, IP networking fundamentals, CCNA subnetting, computer networking basics, nerd cafe , نرد کافه

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