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Networking Interview Questions and Answers

Networking interview questions and answers

What is a network?
It is a set of devices connected by communication links. A node can be a computer or any other device capable of sending and/or receiving data generated by other nodes on the network.

What is MAC address?
The address for a device as it is identified at the Media Access Control (MAC) layer in the network architecture. MAC address is usually stored in ROM on the network adapter card and is unique.

What is IP address?
Ans: The internet address (IP address) is 32bits that uniquely and universally defines a host or router on the internet.
The portion of the IP address that identifies the network is called netid. The portion of the IP address that identifies the host or router on the network is called hostid.

What is the range of addresses in the classes of internet addresses?
Class A 0.0.0.0-----126.255. 255. 255
Class B 128.0.0.0----191. 255. 255. 255
Class C 192.0.0.0------223.255. 255. 255
Class D 224.0.0.0-----239.255. 255. 255
Class E 240.0.0.0------254.255. 255. 255

What is TCP/IP?
Transmission ControlProtocol/Internet Protocol, the suite of communications protocols used to connect hosts on the Internet. TCP/IP uses several protocols, the two main ones being TCP and IP. TCP/IP is built into the UNIX operating system and is used by the Internet, making it the de facto standard for transmitting data overnetworks. Even network operating systems that have their own protocols, such as Netware, also support TCP/IP.

Define LAN, MAN and WAN.
LAN
- A local area network (LAN) is a privately owned and links the devices in a single office,
building or campus.
It allows resources to be shared between personal computers and work stations.
MAN- A metropolitan-area network (MAN) spreads over an entire city.
It may be wholly owned and operated by a private company, eg local telephone company.
WAN – A wide area network (WAN) provides long distance transmission of data, voice, image and video information over large geographic areas that comprise a country, a continent or even whole world.

what is OSI layer?
The OSI, or Open System Interconnection, model defines a networking framework for implementing protocols in seven layers. Control is passed from one layer to the next, starting at the application layer in one station, and proceeding to the bottom layer, over the channel to the next station and back up the hierarchy.
Upper layers -
7. application
6. presentation
5. session
Lower layers -
4. transport
3. network
2. data link
1. physical
1. The Physical Layer describes the physical properties of the various communications media, as well as the electrical properties and interpretation of the exchanged signals. Ex: this layer defines the size of Ethernet coaxial cable, the type of BNC connector used, and the termination method.
2. The Data Link Layer describes the logical organization of data bits transmitted on a particular medium. Ex: this layer defines the framing, addressing and checksumming of Ethernet packets.
3. The Network Layer describes how a series of exchanges over various data links can deliver data between any two nodes in a network. Ex: this layer defines the addressing and routing structure of the Internet.
4. The Transport Layer describes the quality and nature of the data delivery. Ex: this layer defines if and how retransmissions will be used to ensure data delivery.
5. The Session Layer describes the organization of data sequences larger than the packets handled by lower layers. Ex: this layer describes how request and reply packets are paired in a remote procedure call.
6. The Presentation Layer describes the syntax of data being transferred. Ex: this layer describes how floating point numbers can be exchanged between hosts with different math formats.
7. The Application Layer describes how real work actually gets done. Ex: this layer would implement file system operations.

what is network switch?
A network switch or switching hub is a computer networking device that connects network segments.

What is the difference between a managed and an unmanaged switch?
A managed switch offers more functionality than an unmanaged one. For example, I know of at least 2 network admins who use managed switches simply because they can buy a massive switch and maybe have 7 or 8 ports left over and then simply disable them. Thus preventing somebody hooking up their laptop and getting access to the network. See the related link for alot more info.

What is Router?
A router is an electronic device that interconnects two or more computer networks, and selectively interchangespackets of data between them. Network router is a device or a piece of software in a computer that forwards and routes data packets along networks. A network router connects at least two networks, commonly two LANs or WANs or a LAN and its ISP network. A router is often included as part of a network switch. A router is located at any where one network meets another, including each point-of-presence on the Internet.

What is a topology?
Ans: Topology of a network is defined as the geometric representation of the relationship of all the links and linking devices (node) to one another.Four basic topologies are star, bus, ring and mesh.
Star – Here each device has a dedicated point to point link only to a central controller called hub.
Bus -It is multipoint. One long cable acts as a backbone to link all the devices in the network.
Ring -Here each device has a dedicated point to point connection only with the two devices on either side of it.
Mesh -Here every device has a dedicated point to point link to every other device.

What is Network Mask?
A network mask is used for determination of what subnet an IP address belongs to. An IP address has network address and the host address. The first two numbers represents the network address and the second two numbers represents the host of the network.

What is subnet?
A generic term for section of a large networks usually separated by a bridge or router.

What is NETBIOS and NETBEUI?
NETBIOS is a programming interface that allows I/O requests to be sent to and received from a remote computer and it hides the networking hardware from applications.

What is RAID?
A method for providing fault tolerance by using multiple hard disk drives.

What is Bandwidth?
Every line has an upper limit and a lower limit on the frequency of signals it can carry. This limited range is called the bandwidth.

What are major types of networks and explain?
* Server-based network
* Peer-to-peer network

Peer-to-peer network, computers can act as both servers sharing resources and as clients using the resources.
Server-based networks provide centralized control of network resources and rely on server computers to provide security and network administration

What are the important topologies for networks?

BUS topology:

In this each computer is directly connected to primary network cable in a single line.
Advantages:
Inexpensive, easy to install, simple to understand, easy to extend.

STAR topology:

In this all computers are connected using a central hub.
Advantages:
Can be inexpensive, easy to install and reconfigure and easy to trouble shoot physical problems.

RING topology:
In this all computers are connected in loop.
Advantages:
All computers have equal access to network media, installation can be simple, and signal does not degrade as much as in other topologies because each computer regenerates it.

What is mesh network?
A network in which there are multiple network links between computers to provide multiple paths for data to travel.

What is NVT (Network Virtual Terminal)?
It is a set of rules defining a very simple virtual terminal interaction. The NVT is used in the start of a Telnet session.
What is RIP (Routing Information Protocol)?
It is a simple protocol used to exchange information between the routers.


What do you mean by network control protocol?
Ans: Network control protocol is a set of protocols to allow the encapsulation of data coming from network layer protocol that requires the services of PPP.

What do you mean by subnetting?
Ans: Subnetting divides one large network into several smaller ones. It adds an intermediate level of hierarchy in IP addressing

What is half-duplex?
Ans: It is the mode of communication between two devices in which flow of data is bi-directional but not at the same time. ie each station can transmit and receive but not at the same time.
E.g walkie-talkies are half-duplex system.

What is full duplex?
Ans: It is the mode of communication between two devices in which flow of data is bi-directional and it occurs simultaneously. Here signals going in either direction share the capacity of the link.
E.g. telephone