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Subnetting Practice Questions Generator

Generate unlimited CCNA-style subnetting practice questions with a seeded worksheet and a full answer key that shows the binary AND working.

Question types
10
Questions
5
Question types
ccna-2026
Seed

Worksheet

  1. 1. How many usable host addresses does 13.95.20.217/24 provide?

    254

    Host bits = 32 − 24 = 8
Addresses = 2^8 = 256
Usable = 256 − 2 (network + broadcast) = 254

  2. 2. How many usable host addresses does 172.21.15.122/25 provide?

    126

    Host bits = 32 − 25 = 7
Addresses = 2^7 = 128
Usable = 128 − 2 (network + broadcast) = 126

  3. 3. What is the broadcast address of 192.168.151.33/23?

    192.168.151.255

    Address  11000000.10101000.10010111.00100001  = 192.168.151.33
Mask     11111111.11111111.11111110.00000000  = 255.255.254.0  (/23)
AND      11000000.10101000.10010110.00000000  = 192.168.150.0
Set every host bit to 1: 11000000.10101000.10010111.11111111 = 192.168.151.255

  4. 4. What is the usable host range of 172.29.245.95/11?

    172.0.0.1 – 172.31.255.254

    Address  10101100.00011101.11110101.01011111  = 172.29.245.95
Mask     11111111.11100000.00000000.00000000  = 255.224.0.0  (/11)
AND      10101100.00000000.00000000.00000000  = 172.0.0.0
Broadcast = 172.31.255.255
First usable = network + 1 = 172.0.0.1; last usable = broadcast − 1 = 172.31.255.254

  5. 5. What is the usable host range of 192.168.160.192/17?

    192.168.128.1 – 192.168.255.254

    Address  11000000.10101000.10100000.11000000  = 192.168.160.192
Mask     11111111.11111111.10000000.00000000  = 255.255.128.0  (/17)
AND      11000000.10101000.10000000.00000000  = 192.168.128.0
Broadcast = 192.168.255.255
First usable = network + 1 = 192.168.128.1; last usable = broadcast − 1 = 192.168.255.254

  6. 6. What is the network address of 172.30.6.43/8?

    172.0.0.0

    Address  10101100.00011110.00000110.00101011  = 172.30.6.43
Mask     11111111.00000000.00000000.00000000  = 255.0.0.0  (/8)
AND      10101100.00000000.00000000.00000000  = 172.0.0.0

  7. 7. What is the broadcast address of 192.168.31.166/19?

    192.168.31.255

    Address  11000000.10101000.00011111.10100110  = 192.168.31.166
Mask     11111111.11111111.11100000.00000000  = 255.255.224.0  (/19)
AND      11000000.10101000.00000000.00000000  = 192.168.0.0
Set every host bit to 1: 11000000.10101000.00011111.11111111 = 192.168.31.255

  8. 8. What is the broadcast address of 192.168.199.254/20?

    192.168.207.255

    Address  11000000.10101000.11000111.11111110  = 192.168.199.254
Mask     11111111.11111111.11110000.00000000  = 255.255.240.0  (/20)
AND      11000000.10101000.11000000.00000000  = 192.168.192.0
Set every host bit to 1: 11000000.10101000.11001111.11111111 = 192.168.207.255

  9. 9. How many /18 subnets fit inside 192.168.0.0/15?

    8 subnets

    Borrowed bits = 18 − 15 = 3
Subnets = 2^3 = 8
Each /18 holds 16,384 addresses (16,382 usable).

  10. 10. What is the broadcast address of 4.215.119.164/29?

    4.215.119.167

    Address  00000100.11010111.01110111.10100100  = 4.215.119.164
Mask     11111111.11111111.11111111.11111000  = 255.255.255.248  (/29)
AND      00000100.11010111.01110111.10100000  = 4.215.119.160
Set every host bit to 1: 00000100.11010111.01110111.10100111 = 4.215.119.167

What is the Subnetting Practice Questions Generator?

This generator produces subnetting drills the way an instructor would: a random address and prefix, then a question asking for the network address, broadcast address, usable host range, usable host count, or how many smaller subnets fit inside a larger one.

  • Seeded generator — the same seed always reproduces the same worksheet
  • Five question types you can mix and match
  • Answer key shows the address, mask and result in dotted binary
  • Blank-worksheet mode with answer lines for printing
  • Questions use realistic RFC 1918 and public address ranges
  • Runs entirely in your browser, so it works offline in a classroom

How to use the Subnetting Practice Questions Generator

  1. 1

    Type a seed, or press "New random seed" for a fresh worksheet.

  2. 2

    Set how many questions you want, from 1 to 50.

  3. 3

    Tick the question types you want to practise — network address, broadcast, host range, host count or subnet counting.

  4. 4

    Untick "Include the answer key" to print a blank worksheet, or leave it on to study the working.

  5. 5

    Copy the worksheet or download it as a plain text file.

About the Subnetting Practice Questions Generator

This generator produces subnetting drills the way an instructor would: a random address and prefix, then a question asking for the network address, broadcast address, usable host range, usable host count, or how many smaller subnets fit inside a larger one. The answer key shows the binary AND step by step so you can see exactly where a wrong answer went astray.

The questions come from a seeded pseudo-random generator, so the same seed always reprints the same worksheet. That means a class can all work from an identical sheet, or you can hand out the questions today and the answer key tomorrow simply by unticking a box.

It is aimed at CCNA, Network+ and university networking students, and at anyone who wants to get quick at subnetting without a calculator. Everything is generated 100% locally in your browser — no account, no upload, and it works offline.

Frequently asked questions

How can I practise subnetting for the CCNA?

Work timed sets of ten questions until you can do a network address in your head in under thirty seconds. Generate a worksheet here, hide the answer key, and check yourself afterwards — the binary working in the key is the fastest way to see which bit position you got wrong.

How do you find the network address of an IP?

Write the address and the subnet mask in binary and AND them together bit by bit: a bit is 1 in the result only if it is 1 in both. Everything under the mask's 1 bits is kept and everything under the 0 bits becomes zero. The answer key shows this line by line for every question.

Why does the same seed give the same questions?

The generator is a small linear congruential generator seeded from the text you type, so it is fully deterministic. Type the same seed on any device and you get the identical worksheet — handy for handing out a class set and the matching key.

How many /28 subnets fit in a /24?

Sixteen. You borrow 28 − 24 = 4 bits, and 2⁴ = 16, each /28 holding 16 addresses of which 14 are usable. The "how many subnets fit" question type drills exactly this calculation.

Are the questions the same difficulty as the real exam?

They cover the same skills — network and broadcast addresses, host ranges, host counts and subnet counting — using prefixes from /8 to /29. Exam questions tend to wrap this maths in a scenario, so treat these as speed drills for the underlying calculation rather than as exam simulations.

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