CCNA (Cisco Certified Network Associate) is certificate must obtain by any IT professional who want to specialize in Cisco products. The certificate validates the ability to install, configure, operate, and troubleshoot medium-size route and switched networks, including implementation and verification of connections to remote sites in a WAN.

A CCNA certified network engineer will be able to configure and troubleshoot a small network. Expand the switched network from small LAN to medium-size LAN with multiple swithces. Fast and efficient LAN is important in today communication. The engineer also know how to configure OSPF and EIGRP. OSPF is widely used interior gateway protocol in enterprise networks.

EIGRP is a Cisco proprietary routing protocol implemented in routers, which minimize both the routing instability incurred after topology changes, as well as the use of bandwidth and processing power in the router.

A professional must pass Cisco exam #640-802 CCNA, or combined passing scores on both the ICND1 #640-822 and ICND2 #640-816 exams. If you only pass ICND1 #640-822, you can get Cisco Certified Entry Networking Technician (CCENT) certification.

CCNA certifications will be expired in 3 years. One must recertify by passing ONE of following:-
Pass the current ICND2 exam, or
Pass the current CCNA exam, or
Pass the current CCDA DESGN exam, or
Pass any current CCNA Concentration exam (wireless, or security, or voice, or SP Ops), or
Pass any current 642-XXX Professional level exam, or
Pass any current Cisco Specialist exam (excluding Sales Specialist exams or MeetingPlace Specialist exams or Implementing Cisco TelePresence Installations exams or Cisco Leading Virtual Classroom Instruction exams), or
Pass any current CCIE Written Exam, or
Pass the current CCDE Written Exam OR current CCDE Practical Exam, or
Pass the Cisco Certified Architect (CCAr) interview AND the CCAr board review to extend lower certifications

The Cisco Learning Network is a very good place to start your CCNA exposure. The learning portal covers area like ICND1, ICND2, CCNA Composite, CCNA Security, CCNA SP Ops, CCNA Voice, CCNA Wireless. You can also find a Chinese version.

Network engineer is one of high demand jobs in the market. One can be paid very high if he or she achieves CCIE. The hierarchy level is from CCENT, to CCNA, to CCNP, to CCIE, and lastly Architect. One may finish their exam at their own pace. You may choose self-study, or go to take exam in training classes. Besides the hierarchy, one can also take exam to specialize in Data Centre, Security and more.

For a quick introduction on ICND1, here is the course outline:
Module 1: Building a Simple Network
Module 2: Ethernet LANs
Module 3: WLANs
Module 4: LAN Connections
Module 5: WAN Connections
Module 6: Network Environment Management Capstone Lab: Network Environment Management Lab Guide

And ICND2 course outline:
Module 1: Small Network Implementation
Module 2: Medium-Sized Switched Network Construction
Module 3: Medium-Sized Routed Network Construction
Module 4: Single-Area OSPF Implementation
Module 5: EIGRP Implementation
Module 6: Access Control Lists
Module 7: Address Space Management
Module 8: LAN Extension into a WAN