Basic Networking Interview Questions

8/17/2019 Basic Networking Interview Questions

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basic networking interview questionsWhat is ping? Why you use ping?

PING Stands for Packet Inter Net Gopher. PING is used for connectivity checking of any network or any host or device

of any or other networks.

Routers are always preferrable for routing services. Routers work at which OSI layers?

Router works at network layer for providing routing services between or among several networks.

gateway works in which layer?

Transport layer of SI model.

!ow can you check the connectivity of any network?

!y using ping command.

What is a gateway?

" gateway acts a door for the packet to reach the #outside$ of the internal network.

What are the "ifferences a#ong router$ switch$ bri"ge an" hub?

Router% switch% bridge and hub are network devices. &et there are some differences among them. The main

differences are'

• Router% " layer ( device% can work on physical% data and network layer.

• Switch% " layer ) device% can work on data link layer

• &ri"ge% " layer ) device% can work on data link layer.

• !ub% " layer *device% +ust a multi,port repeater and works on physical layer

What is the range of class a""ress?

-,*) is the range of class " address.

'ell an IP which has class ( range. lso tell why that IP is an class ( a""ress.

• IP of /lass /' *0(.*.*.*

• 1hy this is a class / address' /lass / addresses have the range of *0) , ))(

Na#e a "evice which can operate at physical layer of OSI #o"el.

2ub.

Note% Remember% hub is the device that can work only into the physical layer of SI model. !ut switch% router can

also be used instead of a hub. So% all the answers hub% switch or router are all correct.

What is the #a)or "ifferences between a router an" a switch?


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" router can divide the broadcast domain and collision domain. !ut a switch can only divide the collision domain.

Router can communicate among different networks where as the switch can not communicate different networks.

!ub operates at which layers of OSI #o"el? Is it wise to use a hub for huge networks? Why or why not?

• 2ub operates at only physical layer of SI model.

• No% it3s not so wise to use hub for a huge network.

• 2ubs can3t divide the broadcast domain or the collision domain. So% if we use hubs then there creates huge

broadcast domain. 1hen there are huge broadcast% the network gets problem time to time. So% it3s not wise to use

hubs to support a huge network.

!ow #any layers are in OSI #o"el? Na#e the#

There are seven layers of SI model. The layers are'

*. "pplication layer

). Presentation layer

(. Session layer

4. Transport layer

5. Network layer

6. 7ata link layer

. Physical layer

Note% &ou can remember the seven layer model by a simple sentence. P lease D o N ot T ouch S teven's P et A lligator .

See% the starting of each word forms the layer.

Why "o you nee" to use a router?

Router can easily divide the broadcast domain and collision domain. So% to communicate among several networks%

routers are used.

What is the secon" layer of OSI #o"el?

7ata 8ink layer.

Na#e two network "evices which can work as layer * "evice.

Switch and router

What is OSI #o"el?


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SI revers for Open Syste# Interconnection Reference +o"el. It is an abstract model for layered communications

and computer network protocol design. There are seven layers of SI model which% from top to bottom% are the

"pplication% Presentation% Session% Transport% Network% 7ata,8ink% and Physical 8ayers.

SI model also referred as OSI layere" #o"el% OIS layere" technology% , layer #o"el$ OSI seven layer

#o"el% OSI reference #o"el.

What is the "ata unit of -ata ink layer?

9rame

What are the "ifference between '(P an" /-P?

• '(P% /onnection oriented protocol% acknowledged one% Point to point communication.

• /-P% /onnection less protocol% unreliable% less traffic

What is the port no of -NS an" 'elnet?

• 7NS port no' 5(

• Telnet port no' )(

What is the port no of S+'P an" POP0?

• S:PT port no' )5

• PP( port no' **-

What is the functionality of network layer? Na#e the "ata unint of network layer.

•

9unctionality of network layer' Path determination and logical addressing

• 7ata unit of network layer' Packet

Which three layers of OSI #o"el is treate" as 1+e"ia ayers1?

Physical layer% data link layer and network layer are treated as ;:edia 8ayers;.

What is "ea"lock?

7eadlock is a situation when two or more processes are waiting indefinitely for an event that can be caused by only

one of the waiting processes. The implementation of a semaphore with a waiting


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T/P is reliable and D7P is an unreliable service.

!ow -!(P works?

72/P works by four,steps' B*C IP re


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• Presentation layer

• Session layer

• Transport layer

• Network layer

• 7ata link layer

• Physical layer

(heat (hart% OSI layers functionality

• "pplication layer' Network process to application

• Presentation layer' 7ata representation and encryption

•

Session layer' Interhost communication

• Transport layer' End,to,end connections and reliability

• Network layer' Path determination and logical addressing

• 7ata link layer' Physical addressing

• Physical layer' :edia% signal and binary transmission

(heat (hart% '(P4IP reference #o"el

T/P>IP reference model has four layers'

• "pplication

• Transport

• Internet

• Network "ccess

(heat (hart% -ata /nits of OSI layers

• "pplication layer...........7ata

• Presentation layer.........7ata

• Session layer.................7ata

• Transport layer..............Segment

• Network layer................Packet


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• 7ata link layer...............9rame

• Physical layer................!it

(hear (hart% -efault Port Nu#bers

Service Port No.

• 9TP ,,,,,,,, )-%)*

• SS2 ,,,,,,,, ))

• telnet ,,,,,,,, )(

• S:TP ,,,,,,,, )5

• 7NS ,,,,,,,, 5(

•

72/P ,,,,,,,, 6%6A

• T9TP ,,,,,,,, 60

• 2TTP ,,,,,,,, A-

• PP( ,,,,,,,, **-

• NNTP ,,,,,,,, **0

• NTP ,,,,,,,, *)(

•

I:"P4 ,,,,,,,, *4(

• 87"P ,,,,,,,, (A0

• 2TTPS ,,,,,,,, 44(

• I:"PS ,,,,,,,, 00(

• R"7IDS,,,,,,,, *A*)

• "I: ,,,,,,,, 5*0-

(heat (hart% Public IP a""ress ranges

Every computer in the Internet has an IP address. There are five types of IP address. In the following table% you will

find all the classes of IP address and the class name'

(lass Start a""ress 2inish ""ress

• " -.-.-.- *).)55.)55.)55


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• ! *)A.-.-.- *0*.)55.)55.)55

• / *0).-.-.- ))(.)55.)55.)55

• 7 ))4.-.-.- )(0.)55.)55.)55

• E )4-.-.-.- )55.)55.)55.)55

(heat chart% -efault subnet #ask

In the following section% you will see the default subnet mask of each class'

• 9or /lass "' )55.-.-.-

• 9or /lass !' )55.)55.-.-

• 9or /lass /' )55.)55.)55.-

(heat (hart% Private IP a""ress ranges

Public IP address is not so much. That3s why the concept of private IP arises. In the following% you will find all the

private IP address ranges of all classes.

• 9or /lass "' *-.-.-.- @ *-.)55.)55.)55

• 9or /lass !' *).*6.-.- @ *).(*.)55.)55

• 9or /lass /' *0).*6A.-.- @ *0).*6A.)55.)55

(heat (hart% !ost layers an" #e"ia layers

•

!ost layers% The upper four layers are known as 2ost layers. The layers of host layers includes ' "pplication

layer% Presentation layer% Session layer and Transport layer.

• +e"ia layers% The lower three layers are known as :edia layers. The layers of media layers are ' Network layer%

7ata link layer and Physical layer.

HSRP:

Hot Standby Routing Protocol, a proprietary protocol from Cisco. HSRP is a routing protocol

that provides backup to a router in the event of failure. Using HSRP, several routers are

connected to the same segment of an Ethernet, !!" or token#ring net$ork and $ork

together to present the appearance of a single virtual router on the %&'. (he routers share

the same "P and )&C addresses, therefore in the event of failure of one router, the hosts on

the %&' are able to continue for$arding packets to a consistent "P and )&C address. (he

process of transferring the routing responsibilities from one device to another is transparent

to the user.

VRRP :

Virtual Router Redundancy Protocol, an election protocol that dynamically assigns


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responsibility for one or more virtual router(s) to the VRRP router(s) on a LAN,

allowing several routers on a multiaccess lin to utili!e the same virtual "P address#

A VRRP router is con$gured to run the VRRP protocol in con%unction with one or

more other routers attached to a LAN# "n a VRRP setup, one router is elected as the

master router with the other routers acting as bacups in case of the failure of the

master route

Short notes of OSI layers

Layer7(Application):

To allow access to network resources.

e.g: Telnet, TP. !S, !ISLayer6(presentation):

To translate encrypt and compress datas.

e.g: jpeg, mpeg

Layer5(session):

To estalis!, manage and terminate sessions.

e.g: RP"

Layer"(Transport):

To pro#ide reliale end to end message deli#ery and error reco#ery. e.g: T"P, #$P

Layer$(network layer):

To mo#e packets %rom source to destination to pro#ide internetworking.

e.g: i%, &RP'R&RP'I"(P


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Layer&(datalink layer):

To organi'e its into %rame to pro#ide nodetonode deli#ery.

e.g:ethernet, $$I, PPP, H$)"

Layer(p!ysical layer):

To trans*it bits over a *e+iu* to %rovi+e *echanical an+ electrical s%ecifications.

e.g: iber, coa, -baseT

1) What is a Link?

A link refers to the connectivity between two devices. It includes the type of cables andprotocols used in order for one device to be able to communicate with the other.

2) What are the layers of the OSI reference model?

There are 7 OSI layers: Physical Layer, Data Link Layer, Network Layer, Transport Layer,

Session Layer, Presentation Layer and Application Layer.

3) What is ackone net!ork?

A backbone network is a centralized infrastructure that is designed to distribute differentroutes and data to various networks. It also handles management of bandwidth and various

channels.

") What is a L#$?

LAN is short for Local Area Network. It refers to the connection between computers and

other network devices that are located within a small physical location.

%) What is a node?


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A node refers to a point or joint where a connection takes place. It can be computer or

device that is part of a network. Two or more nodes are needed in order to form a network

connection.

&) What are ro'ters?

Routers can connect two or more network segments. These are intelligent network devices

that store information in its routing table such as paths, hops and bottlenecks. With this info,

they are able to determine the best path for data transfer. Routers operate at the OSI

Network Layer.

() What is oint to oint link?

It refers to a direct connection between two computers on a network. A point to point

connection does not need any other network devices other than connecting a cable to the

NIC cards of both computers.

*) What is anonymo's +,P?

Anonymous FTP is a way of granting user access to files in public servers. Users that are

allowed access to data in these servers do not need to identify themselves, but instead log

in as an anonymous guest.

-) What is s'net mask?

A subnet mask is combined with an IP address in order to identify two parts: the extended

network address and the host address. Like an IP address, a subnet mask is made up of 32

bits.

1.) What is the ma/im'm len0th allo!ed for a ,P cale?


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A single segment of UTP cable has an allowable length of 90 to 100 meters. This limitation

can be overcome by using repeaters and switches.

11) What is data encas'lation?

Data encapsulation is the process of breaking down information into smaller manageable

chunks before it is transmitted across the network. It is also in this process that the source

and destination addresses are attached into the headers, along with parity checks.

12) escrie $et!ork ,oolo0y

Network Topology refers to the layout of a computer network. It shows how devices and

cables are physically laid out, as well as how they connect to one another.

13) What is VP$?VPN means Virtual Private Network, a technology that allows a secure tunnel to be created

across a network such as the Internet. For example, VPNs allow you to establish a secure

dial-up connection to a remoteserver.

1") rie4y descrie $#,5

NAT is Network Address Translation. This is a protocol that provides a way for multiple

computers on a common network to share single connection to the Internet.

1%) What is the 6o of the $et!ork Layer 'nder the OSI referencemodel?

The Network layer is responsible for data routing, packet switching and control of network

congestion. Routers operate under this layer.

1&) 7o! does a net!ork toolo0y a8ect yo'r decision in settin0 ' a

net!ork?

Network topology dictates what media you must use to interconnect devices. It also serves

as basis on what materials, connector and terminations that is applicable for the setup.

1() What is RIP?

RIP, short for Routing Information Protocol is used by routers to send data from one network

to another. It efficiently manages routing data by broadcasting its routing table to all other

routers within the network. It determines the network distance in units of hops.

http://career.guru99.com/category/server/http://career.guru99.com/category/server/


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1*) What are di8erent !ays of sec'rin0 a com'ter net!ork?

There are several ways to do this. Install reliable and updated anti-virus program on all

computers. Make sure firewalls are setup and configured properly. User authentication will

also help a lot. All of these combined would make a highly secured network.

1-) What is $I9?

NIC is short for Network Interface Card. This is a peripheral card that is attached to a PC in

order to connect to a network. Every NIC has its own MAC address that identifies the PC on

the network.

2.) What is W#$?

WAN stands for Wide Area Network. It is an interconnection of computers and devices thatare geographically dispersed. It connects networks that are located in different regions and

countries.

21) What is the imortance of the OSI Physical Layer?

The physical layer does the conversion from data bits to electrical signal, and vice versa.

This is where network devices and cable types are considered and setup.

22) 7o! many layers are there 'nder ,9PIP?

There are four layers: the Network Layer, Internet Layer, Transport Layer and Application

Layer.

23) What are ro/y ser;ers and ho! do they rotect com'ter

net!orks?

Proxy servers primarily prevent external users who identifying the IP addresses of an

internal network. Without knowledge of the correct IP address, even the physical location of

the network cannot be identified. Proxy servers can make a network virtually invisible to

external users.

2") What is the f'nction of the OSI Session Layer?

This layer provides the protocols and means for two devices on the network to communicate

with each other by holding a session. This includes setting up the session, managing


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information exchange during the session, and tear-down process upon termination of the

session.

2%) What is the imortance of imlementin0 a +a'lt ,olerance System?

#re there limitations?

A fault tolerance system ensures continuous data availability. This is done by eliminating a

single point of failure. However, this type of system would not be able to protect data in

some cases, such as in accidental deletions.

2&) What does 1.ase


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connect and communicate with one another. One layer may deal with the physical media

used, while another layer dictates how data is actually transmitted across the network.

31) What is the 'rose of cales ein0 shielded and ha;in0 t!isted

airs?

The main purpose of this is to prevent crosstalk. Crosstalks are electromagnetic

interferences or noise that can affect data being transmitted across cables.

32) What is the ad;anta0e of address sharin0?

By using address translation instead of routing, address sharing provides an inherent

security benefit. That’s because host PCs on the Internet can only see the public IP address

of the external interface on the computer that provides address translation and not the

private IP addresses on the internal network.

33) What are =#9 addresses?

MAC, or Media Access Control, uniquely identifies a device on the network. It is also known

as physical address or Ethernet address. A MAC address is made up of 6-byte parts.

3") What is the e>'i;alent layer or layers of the ,9PIP #lication

layer in terms of OSI reference model?

The TCP/IP Application layer actually has three counterparts on the OSI model: the Session

layer, Presentation Layer and Application Layer.

3%) 7o! can yo' identify the IP class of a 0i;en IP address?

By looking at the first octet of any given IP address, you can identify whether it’s Class A, B

or C. If the first octet begins with a 0 bit, that address is Class A. If it begins with bits 10 then

that address is a Class B address. If it begins with 110, then it’s a Class C network.

3&) What is the main 'rose of OSP+?

OSPF, or Open Shortest Path First, is a link-state routing protocol that uses routing tables to

determine the best possible path for data exchange.

3() What are re!alls?


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Firewalls serve to protect an internal network from external attacks. These external threats

can be hackers who want to steal data or computer viruses that can wipe out data in an

instant. It also prevents other users from external networks from gaining access to the

private network.

3*) escrie star toolo0y

Star topology consists of a central hub that connects to nodes. This is one of the easiest to

setup and maintain.

3-) What are 0ate!ays?

Gateways provide connectivity between two or more network segments. It is usually a

computer that runs the gateway software and provides translation services. This translation

is a key in allowing different systems to communicate on the network.

".) What is the disad;anta0e of a star toolo0y?

One major disadvantage of star topology is that once the central hub or switch get

damaged, the entire network becomes unusable.

"1) What is SLIP?

SLIP, or Serial Line Interface Protocol, is actually an old protocol developed during the early

UNIX days. This is one of the protocols that are used for remote access.

"2) @i;e some e/amles of ri;ate net!ork addresses5

10.0.0.0 with a subnet mask of 255.0.0.0

172.16.0.0 with subnet mask of 255.240.0.0

192.168.0.0 with subnet mask of 255.255.0.0

"3) What is tracert?

Tracert is a Windows utility program that can used to trace the route taken by data from the

router to the destination network. It also shows the number of hops taken during the entire

transmission route.

"") What are the f'nctions of a net!ork administrator?


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A network administrator has many responsibilities that can be summarize into 3 key

functions: installation of a network, configuration of network settings, and

maintenance/troubleshooting of networks.

"%) escrie at one disad;anta0e of a eer to eer net!ork5

When you are accessing the resources that are shared by one of the workstations on the

network, that workstation takes a performance hit.

"&) What is 7yrid $et!ork?

A hybrid network is a network setup that makes use of both client-server and peer-to-peer

architecture.

"() What is 79P?

DHCP is short for Dynamic Host Configuration Protocol. Its main task is to automatically

assign an IP address to devices across the network. It first checks for the next available

address not yet taken by any device, then assigns this to a network device.

"*) What is the main 6o of the #RP?

The main task of ARP or Address Resolution Protocol is to map a known IP address to a

MAC layer address.

"-) What is ,9PIP?

TCP/IP is short for Transmission Control Protocol / Internet Protocol. This is a set of protocol

layers that is designed to make data exchange possible on different types of computer

networks, also known as heterogeneous network.

%.) 7o! can yo' mana0e a net!ork 'sin0 a ro'ter?

Routers have built in console that lets you configure different settings, like security and data

logging. You can assign restrictions to computers, such as what resources it is allowed

access, or what particular time of the day they can browse the internet. You can even put

restrictions on what websites are not viewable across the entire network.


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%1) What rotocol can e alied !hen yo' !ant to transfer les

et!een di8erent latformsA s'ch et!een $IB systems and Windo!s

ser;ers?

Use FTP (File Transfer Protocol) for file transfers between such different servers. This ispossible because FTP is platform independent.

%2) What is the 'se of a defa'lt 0ate!ay?

Default gateways provide means for the local networks to connect to the external network.

The default gateway for connecting to the external network is usually the address of the

external router port.

%3) One !ay of sec'rin0 a net!ork is thro'0h the 'se of ass!ords5

What can e considered as 0ood ass!ords?

Good passwords are made up of not just letters, but by combining letters and numbers. A

password that combines uppercase and lowercase letters is favorable than one that uses all

upper case or all lower case letters. Passwords must be not words that can easily be

guessed by hackers, such as dates, names, favorites, etc. Longer passwords are also better

than short ones.

%") What is the roer termination rate for ,P cales?

The proper termination for unshielded twisted pair network cable is 100 ohms.

%%) What is netstat?

Netstat is a command line utility program. It provides useful information about the current

TCP/IP settings of a connection.

%&) What is the n'mer of net!ork Is in a 9lass 9 net!ork?

For a Class C network, the number of usable Network ID bits is 21. The number of possible

network IDs is 2 raised to 21 or 2,097,152. The number of host IDs per network ID is 2

raised to 8 minus 2, or 254.

%() What haens !hen yo' 'se cales lon0er than the rescried

len0th?


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Cables that are too long would result in signal loss. This means that data transmission and

reception would be affected, because the signal degrades over length.

%*) What common soft!are rolems can lead to net!ork defects?

Software related problems can be any or a combination of the following:

– client server problems

– application conflicts

– error in configuration

– protocol mismatch

– security issues

– user policy and rights issues

%-) What is I9=P?

ICMP is Internet Control Message Protocol. It provides messaging and communication for

protocols within the TCP/IP stack. This is also the protocol that manages error messages

that are used by network tools such as PING.

&.) What is Pin0?

Ping is a utility program that allows you to check connectivity between network devices on

the network. You can ping a device by using its IP address or device name, such as a

computer name.

&1) What is eer to eer?

Peer to peer are networks that does not reply on a server. All PCs on this network act as

individual workstations.

&2) What is $S?

DNS is Domain Name System. The main function of this network service is to provide host

names to TCP/IP address resolution.

&3) What ad;anta0es does er otics ha;e o;er other media?

One major advantage of fiber optics is that is it less susceptible to electrical interference. It

also supports higher bandwidth, meaning more data can be transmitted and received.

Signal degrading is also very minimal over long distances.


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&") What is the di8erence et!een a h' and a s!itch?

A hub acts as a multiport repeater. However, as more and more devices connect to it, it

would not be able to efficiently manage the volume of traffic that passes through it. A switch

provides a better alternative that can improve the performance especially when high trafficvolume is expected across all ports.

&%) What are the di8erent net!ork rotocols that are s'orted y

Windo!s RR#S ser;ices?

There are three main network protocols supported: NetBEUI, TCP/IP, and IPX.

&&) What are the ma/im'm net!orks and hosts in a class #A and 9

net!ork?

For Class A, there are 126 possible networks and 16,777,214 hosts

For Class B, there are 16,384 possible networks and 65,534 hosts

For Class C, there are 2,097,152 possible networks and 254 hosts

&() What is the standard color se>'ence of a strai0ht


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(1) What is the di8erence et!een a strai0ht


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Ethernet is one of the popular networking technologies used these days. It was developed

during the early 1970s and is based on specifications as stated in the IEEE. Ethernet is

used in local area networks.

(*) What are some dra!acks of imlementin0 a rin0 toolo0y?

In case one workstation on the network suffers a malfunction, it can bring down the entire

network. Another drawback is that when there are adjustments and reconfigurations needed

to be performed on a particular part of the network, the entire network has to be temporarily

brought down as well.

(-) What is the di8erence et!een 9S=#9 and 9S=#9#?

CSMA/CD, or Collision Detect, retransmits data frames whenever a collision occurred.

CSMA/CA, or Collision Avoidance, will first broadcast intent to send prior to data

transmission.

*.) What is S=,P?

SMTP is short for Simple Mail Transfer Protocol. This protocol deals with all Internal mail,

and provides the necessary mail delivery services on the TCP/IP protocol stack.

*1) What is m'lticast ro'tin0?

Multicast routing is a targeted form of broadcasting that sends message to a selected group

of user, instead of sending it to all users on a subnet.

*2) What is the imortance of Dncrytion on a net!ork?

Encryption is the process of translating information into a code that is unreadable by the

user. It is then translated back or decrypted back to its normal readable format using a

secret key or password. Encryption help ensure that information that is intercepted halfway

would remain unreadable because the user has to have the correct password or key for it.

*3) 7o! are IP addresses arran0ed and dislayed?

IP addresses are displayed as a series of four decimal numbers that are separated by

period or dots. Another term for this arrangement is the dotted decimal format. An example

is 192.168.101.2


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*") D/lain the imortance of a'thentication5

Authentication is the process of verifying a user’s credentials before he can log into the

network. It is normally performed using a username and password. This provides a secure

means of limiting the access from unwanted intruders on the network.

*%) What do mean y t'nnel mode?

This is a mode of data exchange wherein two communicating computers do not use IPSec

themselves. Instead, the gateway that is connecting their LANs to the transit network

creates a virtual tunnel that uses the IPSec protocol to secure all communication that

passes through it.

*&) What are the di8erent technolo0ies in;ol;ed in estalishin0 W#$

links?

Analog connections – using conventional telephone lines; Digital connections – using

digital-grade telephone lines; switched connections – using multiple sets of links between

sender and receiver to move data.

*() What is one ad;anta0e of mesh toolo0y?

In the event that one link fails, there will always be another available. Mesh topology is

actually one of the most fault-tolerant network topology.

**) When tro'leshootin0 com'ter net!ork rolemsA !hat common

hard!are


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Instead of having to visit each client computer to configure a static IP address, the network

administrator can apply dynamic host configuration protocol to create a pool of IP addresses

known as scopes that can be dynamically assigned to clients.

-1) D/lain role in terms of net!orkin0 concet?

Profiles are the configuration settings made for each user. A profile may be created that puts

a user in a group, for example.

-2) What is sneakernet?

Sneakernet is believed to be the earliest form of networking wherein data is physically

transported using removable media, such as disk, tapes.

-3) What is the role of IDDD in com'ter net!orkin0?

IEEE, or the Institute of Electrical and Electronics Engineers, is an organization composed

of engineers that issues and manages standards for electrical and electronic devices. This

includes networking devices, network interfaces, cablings and connectors.

-") What rotocols fall 'nder the ,9PIP Internet Layer?

There are 4 protocols that are being managed by this layer. These are ICMP, IGMP, IP and

ARP.

-%) When it comes to net!orkin0A !hat are ri0hts?

Rights refer to the authorized permission to perform specific actions on the network. Each

user on the network can be assigned individual rights, depending on what must be allowed

for that user.

-&) What is one asic re>'irement for estalishin0 VL#$s?

A VLAN requires dedicated equipment on each end of the connection that allows messages

entering the Internet to be encrypted, as well as for authenticating users.

-() What is IP;&?

IPv6 , or Internet Protocol version 6, was developed to replace IPv4. At present, IPv4 is

being used to control internet traffic, butis expected to get saturated in the near future. IPv6

was designed to overcome this limitation.


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-*) What is RS# al0orithm?

RSA is short for Rivest-Shamir-Adleman algorithm. It is the most commonly used public key

encryption algorithm in use today.

--) What is mesh toolo0y?

Mesh topology is a setup wherein each device is connected directly to every other device on

the network. Consequently, it requires that each device have at least two network

connections.

1..) !hat is the ma/im'm se0ment len0th of a 1..ase


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Architecture iagram Active and Passive *omponents in an "P Networ

In the above diagram, let us assume that there are basically three departments in an

organization that wants to have a LAN across all the departments – IT Department,

Department 1, Department 2. So, if we are to plan for the network components

department wise, for the IT department, we could plan for,

Network rack,

Router, Core switch

Edge Switches (if required)

UTP Patch panel, UTP Patch Cords

Fiber Patch Panel, Fiber Patch Cords

Cat 6/ Cat6A UTP cables

I/O Box with Face Plate, UTP Patch Cords


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PVC Channel – Casing Caping/ Conduits

Fiber Cables (Single Mode or Multi Mode)

The components required in the other two departments would also be similar with theexception of router/ core switch being replaced by distribution/ edge switches.

The above mentioned network components can be broadly divided in to two categories

– Active Components and Passive Components. Active Components are those devices

which required to be supplied with external power (AC/DC/POE etc) in order to function.

They also boost the power of the signals. Passive components do not require to be

provided with any electrical power to work – They just plug on to active components and

transmit/ carry the information (electrical / optical signals).

Active Network Components:

Network Switches:

Network Switches are the basic components of an IP Network. All the network

endpoints (like PC’s, Laptops, Printers, etc) connect to these switches. As the name

goes, they switch (distribute) the data received from one node to any other node in the

network. The network switches come in a variety of configurations, and the popular

ones are mentioned below:

8 Port – 10/100/1000 Mbps

16 Port – 10/100/1000 Mbps

24 Port – 10/100/1000 Mbps

48 Port – 10/100/1000 Mbps

Network switches could also have 10/100 Mbps and POE/Non-POE Port combinations.

They could also have variations in terms of functionalities – Manageable, Semi-

Manageable and Unmanaged Switches. There are even 24/ 48 Port Optical Switches

which connect as many optical connections in addition to the 2/4 ports of the optical

connections that normal switches have.


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The numbers (8, 16 etc.) in the above list refers to the number of Copper UTP

Connectors the switch has, and the switches can connect to as many network devices.

Each such port supports a maximum speed of 10(or)100 / 10(or)100(or)1000 Mbps

depending on the end-point connecting to it (it can auto negotiate to the highest speed

supported by the endpoint). Some ports support POE (Power over Ethernet) which is a

technology to carry the power as well as data to the endpoints, so that the endpoints

need not connect to a separate power source (In the case of Wireless Access Points, IP

Phones etc).

Some network switches are ofUn-managed type – You can just connect the computers

to them, connect them to neighboring switches and extend the network, but beyond that

function, not much functionalities/ management features are supported by them. The

advantages of unmanaged switches are their cost – they are inexpensive.

Some network switches are ofSemi-Managed type – They come with a web browser-

based management interface, limited QoS configurations, VLAN configuration, 802.1x

support and other such limited management features required for the management of

the critical functionalities of the network. But these management features are limited to

what is determined by the manufacturer. These switches are slightly more expensive

than the unmanaged variety but less expensive than fully manageable switches.

Some network switches areFully Manageable – They allow the configurations of

VLAN’s per port, allow VLAN trunking, support web-based management functionalities,

support SNMP/RMON protocols so that each port can be monitored by an SNMP based

network management system, support RSTP (Rapid Spanning Tree Protocol) so that

alternates cabling paths can be created for uplinking, support Link Aggregation so that

couple of cables from individual ports can connect to the uplink switch with double the

speed, support port mirroring for management/ call recording, support stacking and

many other such useful features which help in maintaining a network.

Layer 3 Switches:

As the network becomes bigger and bigger, it becomes difficult to manage all the nodes

using a single layer 2 network segment. One of the main problem with such

unsegmented networks are broadcasts which can create performance bottlenecks on

large networks. Another issue is the spreading of virus and botnets – with a segmented


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network, these remain mostly within their segments. That’s why VLAN’s are advocated

on large networks which segment the network based on the location/ department/

application etc.

But the devices in one segment of the network would need to invariably communicatewith the other segments – Especially in centralized networks where all the servers are

designed to be in a common VLAN and the nodes communicating with them are from

different VLAN’s. In such cases, there needs to be a Layer 3 network device that

performs seamless Inter-VLAN routing without affecting the performance of the network

– This is exactly the reason why Layer-3 switches are required. They are capable of

performing both the Layer 2 Switching and Layer 3 Routing at Line Rate. They also

allow to configure flexible network wide security policies and perform Layer 3 QoS

functionalities which are critical in converged networks which carry a substantial amount

of real-time traffic that require low latency.

Passive Network Components:

Structured Cabling has become quite common for inter-connecting the various active

devices in an IP network. So the following passive components are commonly utilized in

an IP Network for Structured Cabling:

Cat 6 UTP (Un-shielded Twisted Pair) Copper Cables – These are the network cables

that connect a PC/ endpoint to a network switch. Some times, they are also used to provide

inter-connectivity between switches as long as the distance is not greater than 90 meters, which

is the distance they support for transmitting data without using any repeater (repeater function is

provided by using network switches).

Cat 6 UTP Patch Cords – These are one meter/ 2 meter factory crimped cables with

RJ-45 connectors installed at both ends. Actually, the Cat 6 Cables are not recommended to be

directly terminated in either the network switch or the PC/endpoint. Only the patch cordsterminate on both devices and connect to the Cat 6 Network cable through an I/O Box and UTP

patch panel.

Network Rack – Network Racks are either wall mounted or Floor Standing types

depending upon their size. Common sizes of network racks range from 6U to 42U. All the

network equipments are designed in multiples of 1U so as to be accommodated in to these

http://www.excitingip.net/732/what-is-structured-cabling-in-computer-networking-why-do-you-need-it/http://www.excitingip.net/732/what-is-structured-cabling-in-computer-networking-why-do-you-need-it/


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racks with standard fittings. They generally have a width of 19”. The network racks come with a

glass door, lock and key, fans required for cooling, trays, power supplies, cable managers and

all other accessories.

I/O Box and Face Plate: The I/O Box and Face Plate are kept near the computers and a

UTP patch cord is used to connect the Face Plate with the network port in the PC. The Cat 6

UTP cable which comes from the switch terminates in to a permanent connection behind the I/O

Box.

UTP Patch Panel: The UTP Patch Panel is used for terminating all the Cat 6 Cables that

come from various PC’s/endpoints in the network (Actually I/O Box) to the rack. These Cables

are permanently connected behind the UTP Patch Panel and UTP Patch Cords connect from

the respective ports in front to the network switches. This allows for flexible moves, adds and

changes without disturbing the switch ports. All the ports in the patch panel are labelled for easy

identification of which node they are connected to.

Optical Fiber Cables: For carrying data over 90 meters, Optical Fiber Cables are used.

These cables use light for transmission of data instead of the electrical signals used by the UTP

cables. They can carry data for longer distances – even to a few kilo meters without having to

repeat the signals in between. There are two types of cables – Single Mode (Used for higher

bandwidth requirements for longer distances) and Multi Mode (Used for shorter distances). They

connect directly to the Fiber Patch Panel at either end. Usually they come in multiples of 6

Cores – 6 Core, 12 Core, 24 Core being common. For each connection, two cores are used –

one for transmit and another for receive.

Fiber Patch Panel/ Patch Cords: The Optical Fiber Cables are terminated on either

end using the Fiber Patch Panel, Pigtails and Coupler assembly. Actually each core of the Fiber

Cable is spliced to fit in to the Fiber Patch Panel. A Fiber Patch Cord connects to the Patch

Panel and the Fiber interface of the Network Switch. The Fiber interface is usually an SFP Port

over which a Fiber Module is inserted (Mini-Gbic interface). This Fiber Module can connect to

the fiber patch cord directly.

A Wireless network basically utilizes the wireless frequencies (2.4 Ghz or 5 Ghz

spectrum) to transmit the data, voice and video from one point to another using the

wireless signals as the medium – But it is very rare to have a total stand-alone wireless

network as the wireless transmission and reception is restricted from the client

(PC/Laptop/Wi-Fi Phone etc) to the Wireless Access Point. Beyond that, the data is


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carried in the wired backbone network. A look at the below Wi-Fi architecture diagram

would better clarify this point.

+ir

eless Networ Architecture iagram

As shown in the above diagram, the various wireless devices like laptops, computers,

tablets, wi-fi enabled cell phones, wi-fi phones, wireless cameras etc connect to the

wireless access points present in their respective floors and from there, the data is

transmitted over the copper UTP cables to the wired network switch in each department

and then via the optical fiber network to the core switch/ router in the IT Department and

then to the outside world (Internet). So, only the client access is on Wi-Fi technology,

and in rare cases the backbone also could be on wireless technology (with some

limitations) using a wireless mesh. We are talking only about the enterprise campus

wide wireless networks and not about the city-wide or nation wide wireless connectivity.


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So, why are wireless networks required

at all?

Can’t we just have wired network to all the places? We can, but wireless networks have

the following key advantages over wired networks:

Network Access from anywhere: It’s just much more convenient for us to access the

network from any place in the campus and not just our seat alone. Think about it, you go to your

project manager’s room for discussion, and you may want to show something from your laptop.

You go to the conference room or cafeteria and might want to connect to the network. When

laptop’s have become ultra portable, so must the network!

Cost Reduction: In certain places like hostels for example, it does not make sense to

have wires running to each room for Internet connectivity. Its not only the cables but the

additional switch ports, the passive components, I/O boxes, patch cords and so many

components that come along with the wired network. So, having a wireless network in these

high density browsing locations (hot-spots) reduces a lot of cost.

No cluttering of cables: A wireless network certainly eliminates clutter to a huge extant

and makes the place look much more neat.

Good performance/ throughput: With the advent of IEEE 802.11n technology, wireless

networks can now support higher throughput around the range of 300 Mbps. So, even if this

bandwidth gets divided by the number of systems connecting to each access point, we are still

left with a decent throughput. Let’s accept it – 1000 Mbps to the desktop offered by the wired

networks are just not required!!

What do you need in order to set up a

wireless network?

For Small Oice! "ome Oice #SO"O$ #%&%' employees$

If your’s is a home office or a small office (with fewer than 15 users connecting to the

network and within a compact area), then a small stand alone access point costing less


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than 100 USD would suffice your requirement. Just plug it to the wired network switch,

and your network is ready! Some times, the broadband modem which terminates the

broadband line comes with built in modem, and that might also suffice simple wi-fi

requirements.

But always keep in mind that the laptops/ PC’s connecting to the wireless network

should be having IEEE 802.11 a/b/g/n standards based wireless adapters. For laptops,

this comes built-in mostly but for PC’s, you may need to add an USB based / PCMCIA

slot based Wireless adaptor. So, if you are using only PC’s in your network, getting the

wireless adaptors for all of them might increase the cost considerably! Also, some

network devices like printers, servers etc require dedicated wired connectivity. So, keep

these factors in mind while planning for a wireless network in a small office.

For medium si(ed orga)i(atio)s #*+ – %++ employees$:

This is where the confusion comes – should you go for a stand alone access points

based wireless network or a controller based wireless network? Of course, the best

option would be to go for a controller based wireless network (see next section for top

reasons for the same) but this might increase the cost. If you go for a stand-alone

access points based wireless network, you might not only lose a lot of centralized

functionalities, but might also be prone to wireless interference between the neighboring

access points. There are three options you could try in such cases (in case you decideto go for stand alone access points):

Set the frequency of operation for each access point manually so that the neighboring

access points operate in different frequencies (But some access points do not allow to

do this setting and the frequencies are reset every time the access points boot up – due

to power failure for example – so such things need to be taken care of).

Go for stand alone access points that can be upgraded to controller based access

points in the future – This means the access points still are stand alone types and canwork individually without the controller, but when the network grows or there are

excessive maintenance problems, you could buy a controller of the same make and

manage all these access points through it, at a later date. There are a very few vendors

who offer such access points, though.


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Go for access points which supportclustering within the stand-alone access points.

Clustering is a technology that allows the access points to share certain information

within themselves in order to provide some entry level centralized management for all

these access points. But these access points can share information only when each of

them are in range of at least one access point within the cluster group and there is also

limitation in the maximum number of access points that can be part of a cluster group. If

these access points can later on be upgraded to a controller based access points, it is

even better!

For Large Orga)i(atio)s #,ore tha) %++ employees$:

Its highly recommended that larger organizations go with a centralized controller based

wireless solution where the wireless controller is used to provide centralized

management functionalities to all the access points across the network. Below are a list

of top five reasons for the same:

-he -op ' reaso)s to ha.e a wireless co)troller:

Centralized Authentication and Encryption: If you have multiple stand alone access

points at multiple locations, imagine having to update each access point with the list of

MAC addresses that can connect to it. Consider maintaining such a set up as some

employees are going to leave the organization and some will join. And what will happen

to guests who want a temporary access to Internet? Wireless controllers integrate with

centralized corporate directories like Active Directory/ LDAP etc to give user based

authentication (User-name/password and(or) prior installed certificates). This would be

applied to all the users irrespective of which access point they connect to. The guests

can be given a temporary account with which they can access only certain resources

and that too only for a certain time period with a wireless controller. All the

communications between laptops and access points (and) access points and controller

are encrypted for security.

Radio Management and Interference Mitigation: If two neighboring access points

operate in the same frequency, there would be a lot of interference and would result in

loss of data or loss of connections happening frequently. So, wireless controller can

identify which access points are nearer to each other and assign them to operate in

different frequencies. The controller can also do load balancing of users between


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access points and can push the users to another access points if the primary access

point that they connect to, fails.

Network Access Control: Wireless Controller can organize users in to various groups

and enforce certain policies on what network resources they can use and what theycannot. Some users may not be given Internet access but given ERP access and vice

versa, for example.

Roaming: For voice clients like voice over wi-fi phones and dual mode cell phones, it is

very critical that the connection does not terminate when the users are talking over them

and moving across the campus simultaneously. So, controller supports roaming – fast

hand-off of voice sessions to near by access points in order to keep a voice session

from breaking abruptly when it goes beyond the range of one access point.

QoS and Network Visualization: For supporting real time applications like voice and

video, the wireless network needs to support an end-to-end QoS setting for prioritization

of the real time latency sensitive voice and video packets across the network. It would

further help if the wired network is also configured with such QoS prioritization settings.

Controller also allows administrators to see the signal strength levels across their

network in a live heat map – this could be very helpful while maintaining huge wi-fi

networks.

Which is /etter – *01 2h( Spectrum or ' 2h( Spectrum

Wireless devices can connect to the wireless network in either 2.4 Ghz spectrum or 5

Ghz spectrum (depending on which spectrum the wireless adapter in the laptop and the

access point, both support). While 5 Ghz spectrum is more cleaner and is rid of

interference from sources like microwave etc, the commonly available laptops and

access points mostly support only 2.4 Ghz. Actually, 2.4 Ghz spectrum allows only three

non-overlapping channels for IEEE 802.11b/g! But with the advent of IEEE 802.11n

technology, it is now possible to have wireless adaptors and dual radio access pointssupporting both the spectrum’s and the controller can decide (based on the load etc) as

to which is better for individual clients.

What are the wireless sta)dards or Wi&Fi


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IEEE (Institute for Electrical and Electronic Engineers) have drafted certain standards

for wireless equipments and each equipment needs to support one of them or multiples

of them so that they can inter operate with wireless equipments made by other vendors.

The different standards are:

IEEE 802.11 b – This was a very early standard and supports a maximum throughput of

11 Mbps and operates in the 2.4 Ghz spectrum

IEEE 802.11 a – This is a more recent standard supporting a maximum throughput of

54 Mbps and operates in the 5 Ghz spectrum

IEEE 802.11 g – This is the most common standard supporting a maximum throughput

of 54 Mbps and operates in the 2.4 Ghz spectrum – Almost every laptop and access

point should support this.

IEEE 802.11 n – This is the latest standard supporting a maximum throughput of 300

Mbps now and operates in both 2.4 Ghz as well as 5 Ghz spectrum’s.

Note: You cannot get the higher throughput offered by 802.11 n technology by just

replacing the older access points with the newer access points – you need to replace

the client adaptors to support 802.11n as well and you need to upgrade the backbone

wired network to support 1000 Mbps throughput instead of the earlier 100 Mbps. The

latest standards are backward compatible – IEEE 802.11n would support IEEE802.11b/g or/and IEEE 802.11a.

An overview of passive components in

a Local Area Network

This article discusses the advantages of passive components in a network,

introduction to popular passive components like copper cables, optic ber cables

and racks.

Why are Passi;e comonents e/citin0 in a L#$

net!orkE#d;anta0es)?


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F Passi;e comonents ro;ide the hysical connecti;ity et!een the

;ario's net!ork de;ices5

F ,hey ro;ide a medi'm to transfer data in a relati;ely hi0h seed

Eand!idth) et!een the net!ork de;ices5F ,hey hel in connectin0 de;ices o;er 0reater distances5

9oer cales:

Copper cables are the UT ! Unshielded Twisted air Cables which are also called

as Cat" cables in a LAN network. The# are cheaper than ber and faster to set up.

The# don$t re%uire the detailed splicing re%uirements of the ber cables and

an#one with a basic level e"pertise can set them up. The# are ver# common for

connecting the end user computers&laptops&printers etc. to the Network 'witches.

The# are also used in the interconnectivit# of the 'witches and sometimes

interconnectivit# of two separate buildings&departments. The main disadvantage of

copper cables is the distance limitation. The# can give a lossless performance onl#

up to () meters and after that the signals have to be boosted using another switch

or a repeater as the losses tend to be prett# high. There are various categories *Cat+

of UT Copper cables and the popular ones and the bandwidth supported b# them

are given below

Cat- Cables ! 'upport )) /bps up to () meters.

Cat-0 Cables ! 'upport 1 2bps up to () meters.

Cat3a Cables ! 'upport ) 2bps up to () meters.

Cat4a Cables ! 0"pected to support up to 5) 2bps in the future.

The accessories for UT copper cables include patch cord, 675- Connectors,

crimping tools etc.

+ier 9ales:

Unlike the copper cables, which carr# data through electrical signals, the ber

cables carr# data through optical *light+ signals which are propagated through a


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narrow core of the ber, which is a non conductive substance. There are two

modes of ber optic communications ! 'ingle mode and multi mode.

,he ad;anta0es of +ier otic cales:

8 Can propagate the light signals through a longer distance *Usuall# upto 9 :m+ and

in special cases, even higher without the need of a repeater in between to boost the

signals.

8 Can support the higher bandwidth re%uirements of a demanding network as

multiple cores are generall# intertwined in the same cable. 1t uses one core for

transmission and one core for reception of light signals.

8 ;iber optic cables are immune to the 0/1 ! 0lectro /agnetic 1nterference *


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rack+ and come with the cable managers to neatl# carr# cables through them. The#

ma# also come with power connectivit# and fans to cool the network e%uipment

which can generate a lot of heat.

Basic Networking Interview Questions

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