I've tutored over a hundred help desk techs through the CCNA. The exam isn't as hard as people make it out to be — but subnetting is where most people blow it.

Here are the 5 mistakes I see over and over:

1. Memorising subnet masks instead of understanding the math. You need to be able to calculate a /27 in your head in under 10 seconds. If you're still looking at a chart, you're not ready.

2. Confusing network address vs broadcast address. The network address is the first IP in the range with all host bits set to 0. The broadcast is the last with all host bits set to 1. Simple — but under exam pressure, people mix them up.

3. Not practising VLSM. Variable Length Subnet Masking is on the exam. If you've only done fixed-length subnetting, you'll get blindsided.

4. Ignoring the "how many usable hosts" questions. Remember: usable hosts = 2^(host bits) - 2. Always subtract 2 for network and broadcast addresses.

5. Rushing through binary conversion. Converting between decimal and binary needs to be muscle memory. Practice converting random IPs to binary every single day until it's automatic.

If subnetting clicks, the rest of the CCNA falls into place. It's the foundation of everything in networking.

I'm building a full CCNA prep program here on Packet Ready Networking — structured study plans, lab walkthroughs, and a community of people grinding toward the same goal. If you're working help desk and ready to level up, come through.