Class C IP Analysis

Nerd Cafe

Let’s do a step-by-step IP analysis of:

IP: 192.168.1.10/24

We will find:

  • Network IP

  • Broadcast IP

  • First IP (usable)

  • Last IP (usable)

  • Number of available IPs (hosts)

  • Subnet mask

Write IP in binary

Break down each octet to binary:

Octet
Decimal
Binary

1

192

11000000

2

168

10101000

3

1

00000001

4

10

00001010

Full IP in binary:

11000000.10101000.00000001.00001010

Subnet Mask in binary

CIDR = /24

Means:

  • 24 bits for network (all 1’s)

  • 8 bits for host (all 0’s)

Octet
Decimal
Binary

1

255

11111111

2

255

11111111

3

255

11111111

4

0

00000000

Subnet mask:

255.255.255.0

Binary:

11111111.11111111.11111111.00000000

Meaning:

  • First 24 bits = Network part

  • Last 8 bits = Host part

Find Network Address

Rule:

Network Address = IP AND Subnet Mask

IP in binary:

11000000.10101000.00000001.00001010

Subnet Mask:

11111111.11111111.11111111.00000000

Bitwise AND:

11000000.10101000.00000001.00000000

Convert to decimal:

Octet
Binary
Decimal

1

11000000

192

2

10101000

168

3

00000001

1

4

00000000

0

Network Address 

192.168.1.0

Find Broadcast Address

Rule:

Broadcast = Network Address with all host bits = 1

  • Network bits (first 24) stay the same

  • Host bits (last 8) all 1

Binary:

11000000.10101000.00000001.11111111

Decimal:

Octet
Binary
Decimal

1

11000000

192

2

10101000

168

3

00000001

1

4

11111111

255

Broadcast Address

192.168.1.255

First Usable IP

Rule:

First Usable = Network Address + 1

  • Network Address: 192.168.1.0

  • Add 1 to last octet:

192.168.1.1

Binary:

11000000.10101000.00000001.00000001

First Usable IP 

192.168.1.1

Last Usable IP

Rule:

Last Usable = Broadcast - 1

  • Broadcast Address: 192.168.1.255

  • Subtract 1 from last octet:

192.168.1.254

Binary:

11000000.10101000.00000001.11111110

Last Usable IP

192.168.1.254

Number of Usable IPs

Rule:

Usable  IPs=2host  bits−2Usable\;IPs=2^{host\;bits}-2

  • Host bits = 8 (since /24)

  • Calculation:

2^8 = 256
256 - 2 = 254

Number of usable IP

24

Final Answer in Table (with Binary)

Item
Decimal
Binary

Subnet Mask

255.255.255.0

11111111.11111111.11111111.00000000

Network Address

192.168.1.0

11000000.10101000.00000001.00000000

Broadcast Address

192.168.1.255

11000000.10101000.00000001.11111111

First Usable IP

192.168.1.1

11000000.10101000.00000001.00000001

Last Usable IP

192.168.1.254

11000000.10101000.00000001.11111110

Number of Usable IPs

254

(2^8)-2

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