Cisco Network Administration Interview Questions: CISCO CCNA Certification Review

Introduction

Cisco is one of the world's leading networking companies. Cisco specializes in high-end network routers and other infrastructure networking products geared toward the business or enterprise market. The Cisco certification program including the CCNA, CCNP, and CCIE are also recognized worldwide.

Cisco was founded by two students in 1984 who built the first router to allow them to send personal email between two different types of computers. From there, Cisco grew quickly and today employs more than 10,000 people.

Routers

Routers are physical devices that join multiple wired or wireless networks together. Technically, a wired or wireless router is a Layer 3 gateway, meaning that the wired/wireless router connects networks (as gateways do), and that the router operates at the network layer of the OSI model.

Home networkers often use an Internet Protocol (IP) wired or wireless router, IP being the most common OSI network layer protocol. An IP router such as a DSL or cable modem broadband router joins the home's local area network (LAN) to the wide area network (WAN) of the Internet.

By maintaining configuration information in a piece of storage called the routing table, wired or wireless routers also have the ability to filter traffic, either incoming or outgoing, based on the IP addresses of senders and receivers.

Some routers allow the home networker to update the routing table from a Web browser interface. Broadband routers combine the functions of a router with those of a network switch and a firewall in a single unit.

Local Area Network (LAN)

A local area network (LAN) supplies networking capability to a group of computers in close proximity to each other such as in an office building, a school, or a home. A LAN is useful for sharing resources like files, printers, games, or other applications. A LAN in turn often connects to other LANs and to the Internet or other WAN.

Most local area networks are built with relatively inexpensive hardware such as Ethernet cables, network adapters, and hubs. Wireless LAN and other more advanced LAN hardware options also exist.

Specialized operating system software may be used to configure a local area network. For example, most flavors of Microsoft Windows provide a software package called Internet Connection Sharing (ICS) that supports controlled access to LAN resources. The term LAN partly refers to a multiplayer gaming event where participants bring their own computers and build a temporary LAN.

For example, the most common type of local area network is an Ethernet LAN. The smallest home LAN can have exactly two computers; a large LAN can accommodate many thousands of computers. Many LANs are divided into logical groups called subnets. An Internet Protocol (IP) Class A LAN can in theory accommodate more than 16 million devices organized into subnets.

Wide Area Network (WAN)

A WAN spans a large geographic area, such as a state, province, or country. WANs often connect multiple smaller networks, such as local area networks (LANs) or metro area networks (MANs).

The world's most popular WAN is the Internet. Some segments of the Internet, like VPN-based extranets, are also WANs in themselves. Finally, many WANs are corporate or research networks that utilize leased lines.

WANs generally utilize different and much more expensive networking equipment than do LANs. Key technologies often found in WANs include SONET, Frame Relay, and ATM.

Cisco Certified Network Apprentice (CCNA)

CCNA is an entry or apprentice level networking certification. Cisco created the CCNA to recognize basic competency in computer networking, particularly for installation and support of LAN/WAN networks having 100 nodes or fewer. The CCNA covers both IP and non-IP networks including Novell IPX and AppleTalk.

Obtaining the CCNA requires passing a single certification exam. The CCNA exam, newly revised in 2002, contains 55 – 65 questions and lasts approximately 90 minutes. It now costs $125 (USD) to sit the exam.

Although the CCNA has no formal prerequisites, one must effectively complete hundreds of hours of study to prepare. Primarily, one must understand basic routing and switching as they relate to network design, performance, and security.

Cisco offers more advanced certifications like CCNP (Cisco Certified Network Professional) and several varieties of CCIE (Cisco Certified Internetwork Expert) for those who wish to progress beyond the basic CCNA.

Cisco Certified Network Professional (CCNP)

CCNP is a professional or journeyman level networking certification. Cisco created the CCNP to recognize advanced skills in computer networking, particularly for installation and support of medium-sized LAN/WAN networks (having 100 – 500 nodes).

The CCNP focuses on the routing and switching of scalable networks including intranets and campuses. To obtain a CCNP, one must complete either two or four exams that cover routing, switching, remote access, and network support. In total, the exams cost approximately $500 (USD). As with all other Cisco certification exams, it's strongly recommended to prepare for the CCNP by reading study books, taking practice exams on the Web, and getting hands-on experience with Cisco equipment.

One must hold an active CCNA certification to be eligible for a CCNP. After obtaining a CCNP, one may choose to progress to the even more advanced and prestigious CCIE certification.

Cisco Certified Internetwork Expert (CCIE)

CCIE is the most advanced level of networking certification available from Cisco. CCIE is highly prestigious and renowned for its difficulty. Different CCIE certifications can be earned in one of the four following areas:

> Routing and Switching

> Communications and Services

> Security

> Voice

After choosing a specialization, one must complete a two-hour written exam in that area, which costs $300 (USD). CCIE certifications then require completing a full 8-hour long hands-on lab examination that costs $1250 (USD) per sitting.

No other certifications or training courses are CCIE prerequisites. However, in addition to the usual book study, hundreds of hours of hands-on experience with Cisco gear are generally required to adequately prepare for the CCIE.

Sources:

http://compnetworking.about.com/library/glossary/bldef-cisco.htm

http://compnetworking.about.com/cs/routers/g/bldef_router.htm

http://compnetworking.about.com/cs/lanvlanwan/g/bldef_lan.htm

http://compnetworking.about.com/cs/lanvlanwan/g/bldef_wan.htm

http://compnetworking.about.com/od/networkcertifications/l/bldef_ccna.htm

http://compnetworking.about.com/library/glossary/bldef-ccnp.htm

http://compnetworking.about.com/library/glossary/bldef-ccie.htm

Question 1: Routing

What is routing?

A: Routing refers to selecting paths in a computer network along which to send data.

Routing directs forwarding, the passing of logically addressed packets from their source toward their ultimate destination, through intermediary nodes (called routers). The routing process usually directs forwarding on the basis of routing tables within the routers, which maintain a record of the best routes to various network destinations. Thus, the construction of routing tables becomes very important for efficient routing.

Routing differs from bridging in its assumption that address-structures imply the proximity of similar addresses within the network, thus allowing a single routing-table entry to represent the route to a group of addresses. Therefore, routing outperforms bridging in large networks, and it has become the dominant form of path-discovery on the Internet.

Small networks may involve hand-configured routing tables. Large networks involve complex topologies and may change constantly, making the manual construction of routing tables very problematic. Nevertheless, most of the public switched telephone networks (PSTN) use pre-computed routing tables, with fallback routes if the most direct route becomes blocked. (See routing in the PSTN.) Dynamic routing attempts to solve this problem by constructing routing tables automatically, based on information carried by routing protocols, and allowing the network to act nearly autonomously in avoiding network failures and blockages.

Dynamic routing dominates the Internet. However, the configuration of the routing protocols often requires a skilled touch; one should not suppose that networking technology has developed to the point of the complete automation of routing.

Packet-switched networks, such as the Internet, split data up into packets, each labeled with the complete destination address and each routed individually. Circuit switched networks, such as the voice telephone network, also perform routing in order to find paths for circuits (such as telephone calls) over which they can send large amounts of data without continually repeating the complete destination address.

The hardware used in routing includes hubs, switches, and routers.

Question 2: Switching

Can you explain switching?

A: Switching algorithms is relatively simple because it is the same for most routing protocols. In most cases, a host determines that it must send a packet to another host. Having acquired a router's address by some means, the source host sends a packet addressed specifically to a router's physical (Media Access Control [MAC]-layer) address, this time with the protocol (network layer) address of the destination host.

As it examines the packet's destination protocol address, the router determines that it either knows