📘 08-07: Subnetting Examples

🧮 Example 1: Basic Subnetting (/24 → /26)

🔹 Given:

• IP Address: 192.168.1.0
• Default Subnet Mask: /24
• New Subnet Mask: /26

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🔹 Step 1: Identify Borrowed Bits

• Original network bits = 24
• New network bits = 26

• Borrowed bits (n) = 26 − 24 = 2

• Total bits = 32

• Host bits (h) = 32 − 26 = 6

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🧮 Step 2: Number of Subnets

Formula:
Number of subnets = 2ⁿ

→ 2² = 4 subnets

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🧮 Step 3: Number of Addresses and Hosts per Subnet

Total addresses per subnet:
2ʰ = 2⁶ = 64

Usable hosts per subnet:
2ʰ − 2 = 64 − 2 = 62

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🧮 Step 4: Subnet Ranges

• Subnet mask (binary):
  11111111.11111111.11111111.11000000

• Subnet mask (decimal):
  255.255.255.192

• Block size = 256 − 192 = 64

Subnets:

Subnet	Network Address	Broadcast Address
1	192.168.1.0	192.168.1.63
2	192.168.1.64	192.168.1.127
3	192.168.1.128	192.168.1.191
4	192.168.1.192	192.168.1.255

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🧮 Step 5: Host Range (Example: Subnet 1)

• Network ID: 192.168.1.0
• Broadcast ID: 192.168.1.63
• Usable Hosts: 192.168.1.1 → 192.168.1.62

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🧮 Example 2: Subnetting a Class B Network (/16 → /18)

🔹 Given:

• IP Address: 172.16.0.0
• Default Subnet Mask: /16
• New Subnet Mask: /18

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🔹 Step 1: Identify Borrowed Bits

• Original network bits = 16
• New network bits = 18

• Borrowed bits (n) = 18 − 16 = 2

• Total bits = 32

• Host bits (h) = 32 − 18 = 14

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🧮 Step 2: Number of Subnets

Formula:
Number of subnets = 2ⁿ

→ 2² = 4 subnets

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🧮 Step 3: Number of Addresses and Hosts per Subnet

Total addresses per subnet:
2ʰ = 2¹⁴ = 16384

Usable hosts per subnet:
2ʰ − 2 = 16384 − 2 = 16382

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🧮 Step 4: Subnet Ranges

• Subnet mask (binary):
  11111111.11111111.11000000.00000000

• Subnet mask (decimal):
  255.255.192.0

• Block size = 256 − 192 = 64

Subnets:

Subnet	Network Address	Broadcast Address
1	172.16.0.0	172.16.63.255
2	172.16.64.0	172.16.127.255
3	172.16.128.0	172.16.191.255
4	172.16.192.0	172.16.255.255

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🧮 Step 5: Host Range (Example: Subnet 1)

• Network ID: 172.16.0.0
• Broadcast ID: 172.16.63.255
• Usable Hosts: 172.16.0.1 → 172.16.63.254

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💡 Key Idea

Subnetting involves: - borrowing bits
- calculating subnets
- determining host ranges
- identifying network and broadcast addresses

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