If you have a three month window to achieve the CCNA, you will want to manage your time very effectively. I would recommend creating a study schedule that accommodates each of the various exam topics as you progress week by week. Here is that list of exam objectives:
For each of the exam topics, most students like to watch the appropriate videos, then, if applicable, practice the concepts using Hands On Labs. As far as the videos go, many students report success after watching each video at least twice. The first viewing is actively watching and listening, while the second viewing involves careful note taking.
I would also suggest that you leave one week open at the end of your study plan to engage in practice exams and then studying up on your weak areas that the practice exam process can help you identify.
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