There are no formal prerequisites for taking the CCDE, but you should have a thorough understanding of the exam topics before taking the exam.
CCDE candidates are recommended to have five to seven years of experience with designing and architecting network solutions, as well as engaging in other related activities, such as pre-sales work.
You will need to pass the 400-007 CCDE written exam prior to attempting the CCDE lab exam. The written exam validates High-Level Design (HLD) aspects as well as business requirements within the context of enterprise network architecture. The exam is a two-hour, multiple-choice test with 90 to 110 questions that focus on core enterprise network architecture HLD aspects. The exam serves as a prerequisite for the CCDE practical exam and will continue to be available as a means of recertifying your expert-level and lower certifications. The exam is closed book, and no outside reference materials are allowed.