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:

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

• 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