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Networking – Interview Questions

1: What is the primary purpose of a LAN?

The primary purpose of a local-area network LAN is to allow resource sharing. The resources may be
devices, applications, or information. Examples of shared resources are files, databases, e-mail,
modems, and printers.

2: What is a protocol?

When computers communicate with each other, there needs to be a common set of rules and instructions that each computer follows. A specific set of communication rules is called a protocol. Because of the many ways computers can communicate with each other, there are many different protocols — too many for the average person to remember. Some examples of these different protocols include PPP, TCP/IP, SLIP, HTTP, and FTP. Can you guess what the last “P” in each acronym stands for? If you guessed “protocol,” send yourself a congratulations e-mail.

3: What is MAC Address?

A MAC (Media Access Control) address is a hardware identification number that uniquely identifies each device on a network. The MAC address is manufactured into every network card, such as an Ethernet card or Wi-Fi card, and therefore cannot be changed. Because there are millions of networkable devices in existence, and each device needs to have a unique MAC address, there must be a very wide range of possible addresses. For this reason, MAC addresses are made up of six two-digit hexadecimal numbers, separated by colons. For example, an Ethernet card may have a MAC address of 00:0d:83:b1:c0:8e. Fortunately, you do not need to know this address, since it is automatically recognized by most networks.

4: What is a frame?

A frame is a digital “envelope” that provides the information necessary for the delivery of data across a data link. Typical components of a frame are identifiers (addresses) of the source and destination devices on the data link, an indicator of the type of data enclosed in the frame, and error-checking information.

5: What is the purpose of a bridge?

When a road needs to extend across a river or valley, a bridge is built to connect the two land masses. Since the average car cannot swim or fly, the bridge makes it possible for automobiles to continue driving from one land mass to another.

In computer networking, a bridge serves the same purpose. It connects two or more local area networks (LANs) together. The cars, or the data in this case, use the bridge to travel to and from different areas of the network. A bridge can transfer data between different protocols (i.e. a Token Ring and Ethernet network) and operates at the “data link layer” or level 2 of the OSI (Open Systems Interconnection) networking reference model.

6: Differences between LANs and WANs.

  1. LANs are limited to a small geographic area, such as a single building or small campus.
    WANs cover a large geographic area, from citywide to worldwide.
  2. LANs usually consist entirely of privately owned components. Some components of a
    WAN, such as a packet switching network or point-to-point serial links, are usually leased
    from a service provider.
  3. A LAN provides high bandwidth at a relatively cheap price. The bandwidth across a WAN
    is significantly more expensive.

7: What is the purpose of a broadcast MAC identifier? What is the broadcast MAC identifier, in hex
and in binary?

A broadcast MAC identifier, when used as the destination address of a frame, signifies that the data is for all devices attached to the data link. In binary, the broadcast MAC identifier is all ones. In hex, it is ffff.ffff.ffff.

8: What is the primary similarity between a bridge and a router? What is the primary difference
between a bridge and a router?

The primary similarity between a bridge and a router is that both devices increase the number of hosts that may be interconnected into a common communications network. The difference is that a bridge works by interconnecting separate segments of a single network, whereas a router interconnects separate networks.

9: What is a packet? What is the primary similarity between a frame and a packet? What is the
primary difference between a frame and a packet?

A packet is the means by which data is transported from one network to another. The similarity between a frame and a packet is that they both encapsulate data and provide an addressing scheme for delivering the data. The difference between a frame and a packet is that the frame delivers data between two devices sharing a common data link, whereas a packet delivers data across a logical pathway, or route, spanning multiple data links.

 

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