The 640-802 CCNA exam tests knowledge and skills for installing, operating, and troubleshooting small to medium enterprise branch networks. It covers topics such as network fundamentals, OSI and TCP/IP models, network security, routing, switching, VLANs, IP addressing, WAN technologies, and configuration of Cisco routers and switches. Candidates can prepare by taking the ICND1 and ICND2 courses which cover these topics in more depth.