CCNA

CCNA is a popular certification in computer networking developed by Cisco Systems. Cisco created the CCNA to recognize basic competency in installation and support of medium-sized networks.
The core CCNA certification can be obtained by passing a single 90-minute written exam. The exam has no prerequisites, although Cisco and other companies offer various formal training courses to help students prepare. Topics covered on the CCNA exam include

LAN and WAN design (including the OSI model)
IP addressing


The OSI Reference Model is founded on a suggestion developed by the International Organization for Standardization (ISO). The model is known as ISO OSI (Open Systems Interconnection) Reference Model because it relates with connecting open systems – that is, systems that are open for communication with other systems.

OSI Model is a set of protocols that try to identify and homogenize the data communication practices. The OSI Model has the support of most computer and network vendors, many big customers, and most governments, including the United States.

routers and routing protocols (including OSPF, EIGRP and RIP)
VLAN (virtual LAN) and WLAN (wireless LAN)
network security and management (including ACLs)
Separate from the core certification, Cisco also provides separate exams and certs called CCNA Security, CCNA Voice and CCNA Wireless designed to recognize speciality in those respective areas of basic computer networking.