Get a plain-English tutor for subnetting (Network+)

The scenario

Subnetting is the single topic that makes the most Network+ candidates retake the exam. Most study guides explain it with a binary table on page 47 and never look back. AI is uniquely good at this kind of math because you can ask it the same question seven different ways until something clicks. The trick is to ask for a worked example you can follow with your hands, not a definition.

The prompt

You are tutoring me on subnetting for the CompTIA Network+ exam. I learn best with worked examples I can copy and try myself, not with abstract definitions. Walk me through one specific subnetting question step by step.

The question I am stuck on: given the network 192.168.10.0/24, I need to split it into 4 equal-sized subnets. Walk me through what the new prefix is, what the four subnet ranges are, what the broadcast address is for each, and how many usable host addresses each one has.

Rules:
- Show your math at each step, in plain language. Do not skip steps.
- When you use a term (prefix, mask, broadcast, host bits), explain it in five words or less the first time you use it.
- End with three "if I changed the question to..." variants, with the answers, so I can check my pattern recognition.
- Do not assume I know binary. If the math goes binary, show the conversion.
- One worked example. Do not give me five at once.

The output

Step 1: read the question.

The original network is 192.168.10.0/24. The /24 means the first 24 bits are the “network part” (fixed). The last 8 bits are the “host part” (vary per device). With 8 host bits, the original network has 256 addresses (2 to the 8th), of which 254 are usable for hosts (one is the network address, one is the broadcast).

You want 4 equal-sized subnets out of this.

Step 2: figure out the new prefix.

To get 4 subnets, you need to “borrow” 2 bits from the host part to use as subnet bits (because 2 to the 2nd is 4). New prefix = 24 + 2 = /26.

A /26 leaves 6 host bits (32 - 26 = 6). 2 to the 6th is 64. So each new subnet has 64 total addresses, 62 of them usable for hosts.

Step 3: list the four subnet ranges.

Each subnet is 64 addresses wide. Starting from 192.168.10.0, the boundaries land at multiples of 64 in the last octet.

Subnet 1. Network 192.168.10.0/26. Range 192.168.10.0 to 192.168.10.63. Usable hosts 192.168.10.1 to 192.168.10.62. Broadcast 192.168.10.63.
Subnet 2. Network 192.168.10.64/26. Range 192.168.10.64 to 192.168.10.127. Usable hosts 192.168.10.65 to 192.168.10.126. Broadcast 192.168.10.127.
Subnet 3. Network 192.168.10.128/26. Range 192.168.10.128 to 192.168.10.191. Usable hosts 192.168.10.129 to 192.168.10.190. Broadcast 192.168.10.191.
Subnet 4. Network 192.168.10.192/26. Range 192.168.10.192 to 192.168.10.255. Usable hosts 192.168.10.193 to 192.168.10.254. Broadcast 192.168.10.255.

Step 4: pattern check.

Each subnet has 64 total, 62 usable. The first address in each block is the network address (no host gets it). The last is the broadcast (no host gets it). Everything between is fair game.

Variants to try yourself.

Same network, but split into 8 subnets instead. New prefix /27. Each subnet has 32 total, 30 usable. Boundaries at multiples of 32: .0, .32, .64, .96, .128, .160, .192, .224.
Original network is 10.0.0.0/16, split into 4. New prefix /18. Each subnet has 16,384 total, 16,382 usable. Boundaries at 10.0.0.0, 10.0.64.0, 10.0.128.0, 10.0.192.0.
Original network is 172.16.0.0/24, split into 2. New prefix /25. Each subnet has 128 total, 126 usable. Boundaries at 172.16.0.0 and 172.16.0.128.

When you can do all three of those without notes, you are exam-ready on this pattern.

One reasonable answer. Your run may differ. Read it against the scenario before using any of it.

What to watch for

AI sometimes gets subnetting math wrong, especially edge cases (the network address vs. the first usable host, the broadcast address vs. the last usable host). Always verify with a subnet calculator if the answer feels wrong.
If you let AI introduce too many concepts at once, the explanation collapses. Ask one question at a time. Repeat the question with different numbers until you can do it without help.
There is no shortcut for subnetting on the exam. AI tutoring helps you build the pattern; doing 30 problems with paper builds the speed.
Subnetting on Network+ exam day is timed. You will not have AI in the room. Practice without it after you understand the pattern.

← Back to tech use cases