Candidates have the option of gaining the certification by passing two tests (ICND1 640-822 and ICND2 640-816), or one single test (CCNA 640-802); the two-test option has the advantage of allowing the candidate to focus on certain subjects.[1]

The certification is valid for three years; at that time a CCNA holder must either

re-take the CCNA or ICND exam, or
take and pass an exam for one of the Professional (e.g., CCNP) or Specialist level certifications (excluding the sales specialist exams), or pass the CCIE written exam.
These exams are known by their corresponding numbers. When the curriculum of the exam changes the exam number also changes. The current exam number for CCNA is 640-802 (from 15 Aug 2007). New ICND Part1 (640-822 ICND1) and ICND Part2 (640-816 ICND2) available from 15 Aug 2007. Part 1 by itself will give you a CCENT.

These exams are conducted by authorized test centers at a cost of $125 USD each for the ICND1 or ICND2 exams and $150 USD[2] for the full CCNA exam.

There is also the Cisco Networking Academy, which brings the CCNA and CCNP curricula into traditional educational institutions in over 150 countries.[3] Students enrolled in Cisco Networking Academy can request exam vouchers that allow them to take the retired exam for an extended period of time.[4]

Cisco CCNA 640-802 Certification Exam Training Study Guide
Free online study program that includes training courses and materials for Preparation CCNA (Cisco Certified Network Associate) Certification Exam 640-802.

The first stage of Cisco certification system is the entry level and begins with Cisco Certified Entry Networking Technician (CCENT) certification as an interim step to Associate level or directly with CCNA and CCDA certifications. While the CCENT covers basic networking knowledge, and does not get involved with the more intricate technical aspects of the Cisco curriculum it does validate the skills essential for entry-level network support positions. CCENT qualified individuals have the knowledge and skill to install, manage, maintain and troubleshoot a small enterprise branch network, including network security. The CCNA Discovery curriculum covers most of what is required to pass this exam.

Adnan: I will appearing for my CCNA 640-802 exam in about a month. I was enrolled in the Cisco networking academy and completed all my courses with honors. I will be appearing for my voucher exam and then my CCNA paper. What are the topics that I should be concentrating on. This is an urgent matter and any help will be greatly appreciated. I have about a month.

Rainofkayos: For the ccna u should know ip addressing very good, u should be able to break them down no calculator no internet, subnetting, u should know routing protocols interior for the most part, u should know the cisco cli,, solving common issues using commands, access control lists and there syntax, and u should be able to maneuver in a lab environment where u are put in situations, should know ur layer 2 stuff switching and what have u,, should know about (just about not verbose just be aware of) various protocols and their usages, ATM, PPP, Frame Relay, DSL, Cable Modem, Dial up Modem, should know ofcourse the routers internals nvram, flash, rom, registers, basic router configs etc, =) good luck!

From
http://exam-test-blog.org/impt-topics-for-ccna-640-802-examination/