Magic number subnetting is a shortcut technique used in IP subnetting to quickly determine subnet ranges and broadcast addresses without converting between binary and decimal repeatedly. It’s especially useful for Class C networks, but it can apply to any class.

When to Use It

Use magic number subnetting when:

• You're given a subnet mask like /26, /27, etc.

• You want to quickly list subnet ranges, valid host ranges, and broadcast addresses.

Magic number = 256 - interesting octet

The magic number is the size of each subnet block, including:

• 1 network address (aka subnet ID)

• Usable host addresses

• 1 broadcast address

Table

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