Subnet Tools
Subnetting Practice
Unlimited subnetting questions. Type your answer, check it, then see the worked solution.
Question types (8 of 8)
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How it works
Each question uses a random IP address and prefix in the range for the difficulty you pick. Answers come from the same math as the Subnet Calculator on RouteLearn.net, and the worked solution shows the block size method step by step. Everything runs in your browser.
FAQ
- What is the block size method?
- Find the octet where the mask is neither 255 nor 0. Subtract that mask octet from 256 to get the block size. Subnets start at multiples of the block size, so the network address is the multiple at or below the IP's octet, and the broadcast is one less than the next multiple. It's much faster than converting to binary, which is why it's the method most CCNA students use under exam time pressure.
- Why do /31 and /32 never come up?
- They're special cases. A /31 has 2 usable addresses on point-to-point links (RFC 3021) and a /32 is a single host. The drills stick to /8 through /30, where the usual network/broadcast rules apply. The Subnet Calculator handles /31 and /32 if you want to see them.
- How should I enter answers?
- Addresses and masks in dotted-decimal (e.g. 255.255.255.192). Host counts as a number; commas are fine. For the prefix question you can type 26 or /26.
- Is my progress saved?
- Your best streak is saved in this browser on this device only. It won't follow you to another device or browser, and clearing your browser's site data resets it. Nothing is sent to the RouteLearn server.