Understanding Binary - The Foundation of Subnetting
Before you can master subnetting, you need to understand how computers see IP addresses: as 32 binary bits (1s and 0s), not decimal numbers. Click the bits below to toggle them and see how binary converts to decimal!
Interactive Binary-to-Decimal Converter
Click any bit to toggle it on (1) or off (0). Watch how the decimal value changes!
Full IP Address (Dotted Decimal)
0.0.0.0
Key Insight: Each octet is 8 bits. The leftmost bit is worth 128, then 64, 32, 16, 8, 4, 2, 1. Add up all the "on" bits to get the decimal value. The maximum value is 255 (all bits on: 128+64+32+16+8+4+2+1).
Powers of 2 - Your Subnetting Cheat Sheet
Memorize these! They're the building blocks of all subnetting calculations.
20
1
21
2
22
4
23
8
24
16
25
32
26
64
27
128
28
256
Why -2? When calculating usable hosts, always subtract 2 from the total: one address is the network address (all host bits = 0) and one is the broadcast address (all host bits = 1).
Common Subnet Masks Reference
CIDR to Decimal Conversion Table
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Subnet Calculator
Enter an IP address and subnet mask to calculate all subnet details.
Binary Breakdown
Enter an IP address and click Calculate to see the binary breakdown
VLSM Subnet Designer
Variable Length Subnet Masking - efficiently allocate IP space based on actual needs.
Subnet Requirements
VLSM Results
Click "Design VLSM Subnets" to see the allocation
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