It's your worst nightmare.
You've studied hard for your exam so you feel nervous but ready. The exam boots and the first question appears. You then feel your world crashing in around you. Why the #@&% didn't you learn the stuff they are asking in the question?
Some stuff you might not realize is tested because it's so obscure. Some stuff you thought you knew but didn't, at least not well enough. So here's my list of stuff you should know but might feel like skipping for your CCNA exam. Don't say I didn't warn you.
1. Frame Relay
I know it's old and I know it sort of vanished but it's back in full effect. Split horizon, troubleshooting, BECN, and FECN are all there, so know the theory and lab it up.
So just what fiber cable can reach over X metres? What is the name again? You need to know it. Which devices do you connect with crossover cable?
I know! You need to know which layer windowing happens. Where does UDP sit? What about error detection and error correction. It's boring but you need to know. And you need to know how it maps against the TCP model.
4. Spanning Tree
Ah, one which used to be in CCNP but now is in CCNA topics. It sort of slid down.
You need to know how it works, and how to configure and troubleshoot. You need to be able to know how to find the root bridge by logging into a switch or neighbor switch or by looking at diagrams or outputs. Same for RSTP and port roles.
We've gone from “how big is the address” to having to know tunneling methods and which protocols work with it. Not fair maybe, but you have to lay a foundation for the CCNP somewhere!
6. Subnetting and Summarisation
You need to know this cold or you will get a whupping in the exam. Not only that, you need to be fast.
Not only ACLs but also malware, and viruses, as well as when to use an IDS and what does it do?
Everything! STP, NAT, routing, booting problems, and usable tools. Do you know what CDP will show you? Do you know where to find which IP address the VTP information came from?
Hey, I don't want to scare you here but the CCNA exam is a tough mother so, as the Roman army's motto goes “Train Hard – Fight Easy.”