For a number of years the CCNA Exam used to be the entry-level exam that everyone studying to get Cisco Certified would start out with. So why did Cisco a few years ago decide to split the CCNA Exam into two separate tests the ICND1 and the ICND2 that you can take instead of taking the single Exam? I think Cisco had several reasons for doing this.
The first reason is that as time continues to pass on new technologies are invented to improve users communicate over networks. New topics like voice over ip, wireless networking, and broadband Internet didn't really exist a several years ago, but now are more commen than ever. To continue adding topics to the CCNA exam it would be too long or if they ended up covering too many topics with still only 50-75 questions it would be impossible to cover any of the topics in-depth enough to get an accurate testing of your networking knowledge.
I'm sure that over time eventually cisco will phase out the option of taking the single CCNA exam and will require that you start out with the CCENT first as a prerequisite.
The second reason why cisco split up the CCNA exam is because Cisco has targeted high school students to start getting Cisco Certified before they even graduate. This means that usually most of these kids getting certified won't even have job experience. As more and more teenagers starting taking the big Exam and not passing because they lacked the job experience and the years of networking experience that goes a long with it, I think they were finding that too many were failing it.
Realizing the cause of this Cisco came out with the CCENT exam. It is still very difficult but it focuses on only about half of the topics that are on the CCNA Exam. Doing this allows Cisco to test you on more in-depth topics like subnetting, ip addresses, cabling, RIPv2, and other networking fundamentals. They then saved other more advanced topics like Frame Relay, PPP, IPv6, OSPF, EIGRP, and wireless security for the ICND2 exam.
If I were just starting out in networking I would make sure I took the CCENT Exam first rather than starting out with just the CCNA Exam. This way you can focus on just a few topics and really get them down solid before moving onto the next group.
Visit the following link for more information about the CCENT Exam .