There are 2 main entry levels. CCNA (Cisco Certified Network Associate) and CCDA (Cisco Certified Design Associate).

There are hundreds of books out there to get started. You might want to start with something like “CCNA for Dummies”. Usually the books come with some practice questions. You can also purchase Network Simulator software from someone like Boson. This will allow you to get some “hands on” experience if you don’t have access to real routers and switches.

Lastly, after you have learned all you can from the books and software, you can purchase some practice tests from various companies online such as “Pass 4 Sure”. These provide a pool of questions that are very similar to those on the test.

If you study regularly and really commit you can pass your CCNA in less than 6 months.