Interview

This article provides computer networking questions and answers based on networking cable, network topology, Ethernet architecture and IEEE standards for interviews.

What are the differences between STP and UTP cable?

STP cable has an additional layer of insulation on each pair of twisted wires which protects the quality of signals in wires. In positive side STP cable is more reliable. In downside it is more expensive in comparison with UTP cable.

What are the differences between single mode fiber optical cable and multimode fiber optical cable?

SMF (Single Mode Fiber) uses a single ray of light to carry the signals while MMF (Multi Mode Fiber) uses multiple rays of light to carry the multiple signals simultaneously.

What are the differences between baseband and broadband?

Both techniques are used to transmit the data in network wires. Baseband uses bidirectional digital signals for transmission which mean same channel can be used to send and receive data signals. Broadband uses unidirectional analog signals for transmission which means two separate channels will be required for sending and receiving the data.

What is 5-4-3 rule?

10Base2 and 10Base5 Ethernet architecture follows this rule. In this rule there can be maximum five segments in the network, connected with four repeaters. From these five segments only three segments can be populated with nodes.

What are the basic features of 10Base2 Ethernet architecture?

In This architecture 10 stands for speed, Base stands for Baseband transmission and 2 stands for 200 meters (Maximum distance it can span). Basic features of 10Base2 Ethernet architecture are following: -

  • It is used in Bus Topology.
  • It uses Thinnet coaxial cable.
  • Maximum speed of this architecture is 10Mbps.
  • It uses Baseband transmission.
  • Theoretically it supports 200 meter but practically it will supports only 185 meter distance because this architecture uses Thinnet coaxial cable which supports only 185 meter.
  • There can be 30 nodes in each segment.
  • There must be a distance of 0.5 meter between two hosts.

What are the basic features of 10Base5 Ethernet architecture?

In this architecture 10 stands for speed, Base stands for Baseband transmission and 5 stands for 500 meters distance. This architecture can cover 500 meter distance per network segment. It uses Baseband technology for data transmission. It provides maximum 10Mbps speeds. It is used in Bus topology. It uses Thicknet coaxial cable.

Why 10Base2 and 10Base5 Ethernet architecture are no longer used in modern network?

Because both architectures are used in bus topology which is no longer used to build the networks.

What are the basic characteristics of 10BaseT architecture?

This architecture is used in start topology. It provides maximum 10 Mbps speed. It uses Baseband transmission technology and UTP (CAT-3) cable.

What is the 10BaseFL?

The 10BaseFL is the extended version of 10BaseT architecture. It allows us to use fiber optical cable instead of UTP cable. Usually this architecture is used to build the backbone network.

What are the similarity and differences between 100BaseTX and 100BaseFX?

In similar side both architectures use Baseband technology for data transmission and provide a maximum speed of 100Mbps. In difference side 100BaseTx uses UTP (CAT-5) cable while 100BaseFX uses fiber optical cable.

Which standards are used for Gigabit Ethernet?

Gigabit Ethernet uses two standards IEEE802.3z and IEEE802.3ab.

What does the standard IEEE802.3z define?

IEEE802.3z standards define following Gigabit Ethernet implementations: -

  • 1000BaseSX (1000Mbps speed, MMF Fiber optical cable, 550Meter maximum distance)
  • 1000BaseLX (1000Mbps speed, SMF Fiber Optical cable, 3Kilometers distance)
  • 1000BaseCX (1000Mbps speed, coaxial cable, 25meter distance)

What does the standard IEEE802.3ab define?

IEEE802.3ab standard defines 1000BaseTX Ethernet implementation. 1000BaseTX uses UTP (CAT 5e or CAT6) cable. It provides speed of 1000Mbps. Maximum distance covered by this architecture is 100 meter.

What does access method describe?

An access method describes how a computer transmits data in network.

What is the CSMA/CD?

This is mechanism of removing collision from network. When two or more nodes simultaneously sense the wire and found no frame and each device places its frame on the wire. These frame would be collide in wire and a collision will occur.

csma cd process

If the NICs see a collision for their transmitted frames, they have to resend the frames. In this situation, each NIC that was transmitting a frame when a collision occurred creates a special signal, called a jam signal, on the wire, waits a small random time period and examine the wire again. If no frame is currently on the wire, NIC will retransmit its original frame again. This collision detection method is known as CSMA/CD.

Which standard defines Token Ring?

Token Ring is defined in IEEE 802.5 standard.

Which access method Token Ring topology uses?

Token Ring topology uses token passing access method. In this method only the system which has token can send the data.

What are the differences between different Ethernet architectures based on speed, distance and cable?

Architecture Speed Distance Cable
10Base2 10Mbps 185 Meter Thinnet Coaxial cable
10Base5 10Mbps 500 Meter Thicknet Coaxial cable
10BaseT 10Mbps 100 Meter UTP CAT-3 cable
100BaseTX 100 Mbps 100 Meter UTP CAT-5 cable
100BaseFX 100 Mbps 100 Meter Fiber optical cable
1000BaseSX 1000 Mbps 550 Meter MMF Fiber optical cable
1000BaseLX 1000 Mbps 3 Kilometer SMF Fiber optical cable
1000BaseCX 1000 Mbps 25 Meter Coaxial cable
1000BaseTX 1000 Mbps 100 Meter UTP CAT5e or CAT6 cable
10GBaseSR 10 Gbps 100 Meter Short range MMF Fiber optical cable
10GBaseLR 10 Gbps 10 Kilometer Long range MMF Fiber optical cable
10GBaseER 10Gbps 40 Kilometer Extra-long SMF fiber optical cable
10GBaseT 10 Gbps 100 Meter UTP CAT6 cable

A company wants to extend its intranet network to certain business partners. What type of network it has to build?

Extranet, when we extend the intranet to external parties, we create Extranet.

In which topology all nodes have a direct connection to every other node on the network?

In mesh topology all nodes have a direct connection with each node in network.

Which network topology uses terminators?

Bus topology uses terminators to absorb the signals at the end of the cable.

Briefly explain the IEEE standards.

Standard Description
802.1 Standards for LAN/MAN bridging and management
802.2 Standards for Logical Link Control (LLC)
802.3 Ethernet Standards CSMA/CD
802.4 Standards for Token passing bus access
802.5 Standards for token ring access and for communications between LANs and MANs
802.6 Standards for information exchange between systems
802.7 Standards for broadband LAN cabling
802.8 Standards for Fiber optical connection
802.9 Standards for integrated services, like voice and data
802.10 Standards for LAN/MAN security implementations
802.11 Standards for WiFi (Wireless Networking)
802.12 Standards for demand priority access method
802.14 Standards for cable television broadband communications
802.15 Standards for Bluetooth network
802.15 Standards for ZigBee (Wireless Sensor/Control Networks)
802.16 Standards for WiMAX Wireless Networking

What is the maximum distance 10Base2 Ethernet architecture supports?

Theoretically it supports 200 meter distance. Practically it supports only 185 meters. This is because it uses Thinnet coaxial cable which has a distance limitation of 185 meters.

What is the maximum distance limit of UTP cable?

Distance limit of UTP cable is 100 meter.

To build a 100BaseT network which cable is required?

UTP (CAT-5) Cable is required to build the 100BaseT network.

What is the maximum distance which SMF (single mode fiber) cable supports?

The maximum distance which a SMF cable supports is 2KM.

Why fiber cable does not get affected from cross talk?

Cross talk generates in copper wire while fiber cable uses glass to transmit the data which is immune to crosstalk.

Which Ethernet architecture uses BNC connector?

10Base2 and 10Base5 Ethernet architecture use BNC connector.

Which access method is used 1000BaseTX?

CSMA/CD access method is used in 1000BaseTX network.

How many network segments can be populated in 10Base2?

Maximum three network segments can be populated in 10Base2.

Which cable is used in 10BaseFL?

10BaseFL uses fiber optical cable.

In Bus topology to remove a workstation from network, the T connection is removed from NIC. Will this network work normally?

Yes, this network will work normally because physical cable connection is not interrupted.

Which operating system was developed by Bell Labs?

UNIX

A loose terminator gets separated from coaxial cable making it open at one end in Bus topology. Will this network work as expected?

No, this network will not work because from an opened cable signal will not be bounced back.

A cable which was not properly attached with the hub is accidentally pulled out from hub in star topology. Will this network work?

Yes, only the device which was connected with that cable will lose connectivity. Remaining devices work normally.

Due to fluctuation in light a centralized hub is burnt in star topology. Although all connected devices and cables are unaffected, will these devices be able to access the network?

No, in start topology if centralized hub is failed, all devices will lose the connectivity.

A cable which connects two devices in Ring topology broke. Will remaining devices work normally?

No the network will not work. There is no provision for redundant path in Ring network (as per 802.5 specifications) so a break in cable would bring the entire network down.

What is the maximum rate of collision in a healthy Ethernet LAN?

Collision rate should not be more than 30% in a healthy Ethernet.

When a broadcast is made in Ethernet LAN, which devices will examine it?

All devices will examine the broadcast message.

Does broadcast message intended for a specific device in network?

No, broadcast is intended for all devices in network.

Which cable is used in Star topology?

UTP (Unshielded Twisted Pair) Cable

What is main advantage of Mesh topology?

It creates redundant links between nodes which keep alive network till the last active link.

Which mechanism does Ethernet use to avoid the collision?

Carrier Sense Multiple Access/Collision Detection (CSMA/CD).

Why a system cannot monopolize the Token Ring LAN?

Each system gets the token only for a specific time. It must have to release the token to the next system in a particular time.

Which connection method does Wireless 802.11b LAN use?

Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA)

Why do we do the networking?

We do the networking to share the information, resources and applications.

Briefly describe various network types.

Network Description
LAN Local Area Network (LAN) connects computers which reside in a small geographical area such as building or campus.
WAN Wide Area Network (WAN) connects multiple LANs which are separated by a large geographical distance such as different continents
MAN Metropolitan Area Networks (MAN) connects multiple LANs which are separated in a metro city.
CN Content Network is used to cache and distribute the Internet traffic.
SAN Storage Area Network provides high speed infrastructure between storage devices and file servers.
Intranet This is a private network. Outsiders are not allowed to connect in this network.
Extranet This network allows certain services from Intranet to known external users.
Internet This network allows unknown external users to connect with internal resources of network such as web server.
VPN This network provides secure connection across the public network such as Internet.

What is the difference full mesh and partial mesh?

In full mesh all nodes have connection with all nodes which mean each node has a direct connection with all nodes in network. In partial mesh nodes do not require a direct connection with all other nodes.

What is the difference between a server and a dedicate server?

A server is a special privileged computer in network. Usually it built from the most powerful hardware and advanced software available in network. It is responsible to provide the services and resources to client computers in network.

A dedicate server is also a server but it is deployed to provide a specific service. For example, if a server is providing all regular services in network then it is a server. But if it is providing only a specific service such as web server which provides only web service nothing else then it will be considered as a dedicate server.

That’s all for this set of interview questions with answers. In next set I will present more interview questions and answers base on different topic of computer networking.