Specifically for the CCNA 200-120 exam, two big trouble spots are the volume of topics and the ability to troubleshoot using those many concepts. The two-exam path to CCNA Routing and Switching allows you to more easily manage the volume of concepts, and to break up some of the troubleshooting topics. For perspective, while many Cisco exams cover the same topics in a single one-week Cisco authorized course, or in a two-semester course in the Cisco Network Academy, the 200-120 exam covers the same topics found in two one-week authorized Cisco courses.
With the single-exam path using the CCNA 200-120 exam, you must be ready to:
- Configure a variety of features on Cisco routers and switches
- Make a variety of math calculations related to IP Version 4 subnetting, including variable length masking
- Analyze where data flows in a network, based on documentation or command output from routers and switches
- Discover a variety of problems with an existing network, due to the many exam topics that use the word “troubleshoot”
As for the technical topics, this list outlines the top trouble spots by topic:
- IP Version 4 Subnetting and Addressing: The single most challenging technology topic for most candidates.
- Spanning Tree Protocol (STP): In real life, most people have STP enabled, and it works, and there is no need to pay much attention to it. As a result, even people who already work in networking jobs typically learn little about STP on the job.
- Access Control Lists (ACLs): ACLs act as a basic programming language that can be applied to packets flowing through a router for the purpose of filtering some packets (discarding the packets). Implementing ACLs requires mastery of the packet headers, an understanding of packet flow, and an understanding of the logic behind the commands.
- IP Version 6: While many people already know something about IPv4, IP Version 6 (IPv6) is new to most CCNA candidates.
- Open Shortest Path First (OSPF): OSPF is the most complex IP routing protocol included in CCNA. While CCNA only examines the basics of OSPF, its underlying operation differs so much from RIP and EIGRP that it requires a little more thought.
- Packets and Flows: Particularly for those brand new to the networking world, the details of frames, packets, segments, their headers, the flow of packets with end user data, the related overhead processes, all the related terminology, and how it all interacts, can be a big challenge.
- First Hop Redundancy Protocols: Each FHRP allows two routers to sit on a LAN and share a role called the default router or default gateway. Interestingly, the details of how these protocols work requires a high level of mastery of both IP Version 4 as well as LAN switching skills.
The exam environment and question types also pose some big challenges. In particular, time pressure exists in almost every Cisco exam. Like all Cisco exams, the CCNA exam does not allow you to skip a question and go back later, so there's a tendency to take extra time when unsure. The exam includes a couple of types of particularly time-consuming problem types: Sims, Simlets, and Testlets. While a time goal of 1 minute per multichoice question time budget is reasonable, these other questions typically require 4-8 minutes eachbut each counts as 1 question from the overall count of the number of questions. And your speed at finding the answers to subnetting questions will impact whether you feel much time pressure.
Finally, two question typesSims and Simletsrequire you to have practiced and become comfortable with typing commands on a Cisco router or switch CLI as if you were configuring and monitoring real equipment. As a result, most CCNA candidates need hands-on experience before tackling the ICND1, ICND2, and CCNA exams.