Network Calculator Suite
IPv4 Subnet Calculator · IPv6 · VLSM · Binary Converter · Cheat Sheet — all in one place.
CCNA Subnetting Tips
Magic Number Method
Subtract last non-zero octet of subnet mask from 256. That is your block size. Count in that increment to find network boundaries.
Key Masks to Memorize
/24=255.255.255.0 (254 hosts) | /25=128 (126) | /26=192 (62) | /27=224 (30) | /28=240 (14) | /29=248 (6) | /30=252 (2)
Host Formula
Usable hosts = 2ⁿ − 2 where n = host bits. Always subtract 2 for network + broadcast. /24 = 2⁸−2 = 254.
CCNA Exam Focus
Given IP + mask → identify network, broadcast, first/last host, number of hosts. Practice until instant recall.
Private IP Ranges
10.0.0.0/8 · 172.16.0.0/12 · 192.168.0.0/16 — memorize these. RFC 1918 ranges guaranteed on exam.
Quick Win
/30 gives exactly 2 usable hosts — used for point-to-point WAN links. /31 is also valid (RFC 3021) for P2P.
Variable Length Subnet Masking (VLSM)
Enter a base network and subnet requirements. VLSM allocates subnets efficiently from largest to smallest.
IPv6 Quick Reference
::1/128
Loopback — equivalent to 127.0.0.1 in IPv4
fe80::/10
Link-local — auto-configured, not routable
2000::/3
Global unicast — publicly routable addresses
ff00::/8
Multicast — no broadcast in IPv6, replaced by multicast
fc00::/7
Unique local — like RFC 1918 private ranges
/64 standard
LAN prefix — accommodates EUI-64 interface IDs
Binary ↔ Decimal ↔ Hex Converter
Binary Value Table — Memorize These
| Bit Position | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|---|---|---|---|---|
| Value | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 |
| Hex | 80 | 40 | 20 | 10 | 08 | 04 | 02 | 01 |
💡 Add up the values where bits are 1. Example: 11000000 = 128+64 = 192
Complete CIDR Cheat Sheet
| CIDR | Subnet Mask | Wildcard | Hosts | Block Size | Binary Mask | Use Case |
|---|
Calculation History
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