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.