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Master IPv4 subnetting.One bit at a time.

Visual lessons, a subnet calculator and timed drills built on the 60-second method. Made for CCNA and Network+ prep.

Live example
10.44.21.148/25
00001010
10
00101100
44
00010101
21
10010100
148
25 network bits7 host bits
Network
10.44.21.128
Broadcast
10.44.21.255
Usable hosts
126
Block size
128 · octet 4
Your path

From first bit to working engineer.

0/19 skills mastered
Start with Foundations · Beginner

Binary and decimal

Convert any octet between binary and decimal.

New here? Foundations covers binary, masks and host counts. Learn the idea, then drill it until it sticks.

  1. 1
    FoundationsBeginner0/5 mastered

    Binary, masks and the numbers behind every subnet.

  2. 2
    Core subnettingBeginner0/4 mastered

    Find any network, broadcast and host range in your head.

  3. 3
    PlanningIntermediate0/3 mastered

    Size subnets from real requirements.

  4. 4
    Routing decisionsIntermediate0/4 mastered

    How hosts and routers choose where packets go.

  5. 5
    Design and operationsAdvanced0/3 mastered

    VLSM plans, summarization and troubleshooting.

11
visual lessons
19
skills to master
5
calculator tools
16
badges to earn
Everything in one place

Learn it. Check it. Drill it.

Open the Visual Lab:

Visual Lab

Eleven short lessons, from binary to VLSM and summaries. Change an address and watch every bit update live.

  1. 1Binary basics
  2. 2The 7 attributes
  3. 360-second method
  4. 4Bitwise AND
  5. 5Split a network
  6. 6On-link vs gateway
  7. 7Across octets
  8. 8Design with VLSM
  9. + 3 more: summaries, /31 and /32, IPv6
Open the subnet calculator:

Calculator

Split networks, plan VLSM, summarize routes, check overlaps and run route lookups.

192.168.1.0/24 → /26
.0
.64
.128
.192
Start a quiz:

Quizzes

Drill any of 19 skills, four levels, weak-spot mode and a 60-second blitz.

1255.255.255.224
2255.255.255.240
3255.255.255.248
Open practice problems:

Practice

Fresh problems: all 7 attributes, VLSM plans, host troubleshooting and binary drills.

Broadcast address
172.16.47.255
6 of 7 correct
View your progress:

Progress

Accuracy by level and skill, streaks, XP and badges.

Level
1
0No answers yet
Open the VLSM planner:

VLSM planner

Type your LANs and host counts. Get a gap-free plan.

Ready for your first drill?

Start with five questions. Your progress saves in this browser.