Basic Networking Interview Questions with answer

When were OSI model developed and why its standard called 802.XX and so on?

OSI model was developed in February1980 that why these also known as 802.XX Standard (Notice 80 means ==> 1980, 2means ==> February)

What is Full form of ADS?

Active Directory Structure

How will you register and activate windows?

If you have not activated windows XP, you can do so at any time by clicking the windows Activation icon in the system tray to initiate activation. Once you have activated windows XP, this icon disappears from the system tray. 
For registration 
Start ==> Run ==> regwiz /r

Where do we use cross and standard cable?

Computer to computer ==> cross 
Switch/hub to switch/hub ==>cross 
Computer to switch/hub ==>standard

How many pins do serial ports have?

In computer it's known as com port and could be available in 9pin or 25 pin. On router it have 60 pins.

How will check ip address on 98?

Start ==> Run ==> command ==> winipcfg

How will you make partition after installing windows?

My computer ==> right click ==> manage ==> disk management ==> 
select free space ==> right click ==> New partition

What is IP?

It's a unique 32 bits software address of a node in a network.

What is private IP?

Three ranges of IP addresses have been reserved for private address and they are not valid for use on the Internet. If you want to access internet with these address you must have to use proxy server or NAT server (on normal cases the role of proxy server is played by your ISP.).If you do decide to implement a private IP address range, you can use IP addresses from any of the following classes: 
Class A 10.0.0.0 10.255.255.255 
Class B 172.16.0.0 172.31.255.255 
Class C 192.168.0.0 192.168.255.255

What is public IP address?

A public IP address is an address leased from an ISP that allows or enables direct Internet communication.

What's the benefit of subnetting?

Reduce the size of the routing tables. 
Reduce network traffic. Broadcast traffic can be isolated within a single logical network. 
Provide a way to secure network traffic by isolating it from the rest of the network.

What are the differences between static ip addressing and dynamic ip addressing?

With static IP addressing, a computer (or other device) is configured to always use the same IP address. With dynamic addressing, the IP address can change periodically and is managed by a centralized network service

What is APIPA?

Automatic private IP addressing (APIPA) is a feature mainly found in Microsoft operating systems. APIPA enables clients to still communicate with other computers on the same network segment until an IP address can be obtained from a DHCP server, allowing the machine to fully participate on the network. The range of these IP address are the 169.254.0.1 to 169.254.255.254 with a default Class B subnet mask of 255.255.0.0.

What are the LMHOSTS files?

The LMHOSTS file is a static method of resolving NetBIOS names to IP addresses in the same way that the HOSTS file is a static method of resolving domain names into IP addresses. An LMHOSTS file is a text file that maps NetBIOS names to IP addresses; it must be manually configured and updated.

What is DHCP scope?

A scope is a range, or pool, of IP addresses that can be leased to DHCP clients on a given subnet.

What is FQDN?

An FQDN contains (fully qualified domain name) both the hostname and a domain name. It uniquely identifies a host within a DNS hierarchy

What is the DNS forwarder?

DNS servers often must communicate with DNS servers outside of the local network. A forwarder is an entry that is used when a DNS server receives DNS queries that it cannot resolve locally. It then forwards those requests to external DNS servers for resolution.

Which command will you use to find out the name of the pc in networks?

NSLOOKUP [192.168.0.1] 
[Ip of target computer]

How will enable sound service in 2003?

By default this service remain disable to enable this service
Start ==> administrative tools ==> service ==> windows audio ==> start up type ==> automatic

How will enable CD burning service in 2003?

By default this service remain disable to enable this service
Start ==> administrative tools ==> service ==> IMAPI CD burning com service ==> start up type ==> automatic

Networking - Interview Questions and Answers

1. Define Network?

A network is a set of devices connected by physical media links. A network is recursively is a connection of two or more nodes by a physical link or two or more networks connected by one or more nodes.

2. What is a Link?

At the lowest level, a network can consist of two or more computers directly connected by some physical medium such as coaxial cable or optical fiber. Such a physical medium is called as Link.

3. What is a node?

A network can consist of two or more computers directly connected by some physical medium such as coaxial cable or optical fiber. Such a physical medium is called as Links and the computer it connects is called as Nodes.

4. What is a gateway or Router?

A node that is connected to two or more networks is commonly called as router or Gateway. It generally forwards message from one network to another.

5. What is point-point link?

If the physical links are limited to a pair of nodes it is said to be point-point link.

6. What is Multiple Access?

If the physical links are shared by more than two nodes, it is said to be Multiple Access.

7. What are the advantages of Distributed Processing?

a. Security/Encapsulation

b. Distributed database

c. Faster Problem solving

d. Security through redundancy

e. Collaborative Processing

8. What are the criteria necessary for an effective and efficient network?

a. Performance

   It can be measured in many ways, including transmit time and response time. b. Reliability

   It is measured by frequency of failure, the time it takes a link to recover from a failure, and the network's robustness.

c. Security

   Security issues includes protecting data from unauthorized access and virues.

9. Name the factors that affect the performance of the network?

a. Number of Users

b. Type of transmission medium

c. Hardware

d. Software

10. Name the factors that affect the reliability of the network?

a. Frequency of failure

b. Recovery time of a network after a failure

11. Name the factors that affect the security of the network?

a. Unauthorized Access

b. Viruses

12. What is Protocol?

A protocol is a set of rules that govern all aspects of information communication.

13. What are the key elements of protocols?

The key elements of protocols are

a. Syntax

   It refers to the structure or format of the data, that is the order in which they are presented.

b. Semantics

   It refers to the meaning of each section of bits.

c. Timing

   Timing refers to two characteristics: When data should be sent and how fast they can be sent.

14. What are the key design issues of a computer Network?

a. Connectivity

b. Cost-effective Resource Sharing

c. Support for common Services

d. Performance

15. Define Bandwidth and Latency?

Network performance is measured in Bandwidth (throughput) and Latency (Delay). Bandwidth of a network is given by the number of bits that can be transmitted over the network in a certain period of time. Latency corresponds to how long it takes a message to travel from one end off a network to the other. It is strictly measured in terms of time.

16. Define Routing?

The process of determining systematically how to forward messages toward the destination nodes based on its address is called routing.

17. What is a peer-peer process?

The processes on each machine that communicate at a given layer are called peer-peer process.

18. When a switch is said to be congested?

It is possible that a switch receives packets faster than the shared link can accommodate and stores in its memory, for an extended period of time, then the switch will eventually run out of buffer space, and some packets will have to be dropped and in this state is said to congested state.

19. What is semantic gap?

Defining a useful channel involves both understanding the applications requirements and recognizing the limitations of the underlying technology. The gap between what applications expects and what the underlying technology can provide is called semantic gap.

20. What is Round Trip Time?

The duration of time it takes to send a message from one end of a network to the other and back, is called RTT.

21. Define the terms Unicasting, Multiccasting and Broadcasting?

If the message is sent from a source to a single destination node, it is called Unicasting.

If the message is sent to some subset of other nodes, it is called Multicasting.

If the message is sent to all the m nodes in the network it is called Broadcasting.

22. What is Multiplexing?

Multiplexing is the set of techniques that allows the simultaneous transmission of multiple signals across a single data link.

23. Name the categories of Multiplexing?

a. Frequency Division Multiplexing (FDM)

b. Time Division Multiplexing (TDM)

   i. Synchronous TDM

   ii. ASynchronous TDM Or Statistical TDM.

c. Wave Division Multiplexing (WDM)

24. What is FDM?

FDM is an analog technique that can be applied when the bandwidth of a link is greater than the combined bandwidths of the signals to be transmitted.

25. What is WDM?

WDM is conceptually the same as FDM, except that the multiplexing and demultiplexing involve light signals transmitted through fiber optics channel.

26. What is TDM?

TDM is a digital process that can be applied when the data rate capacity of the transmission medium is greater than the data rate required by the sending and receiving devices.

27. What is Synchronous TDM?

In STDM, the multiplexer allocates exactly the same time slot to each device at all times, whether or not a device has anything to transmit.

28. List the layers of OSI

a. Physical Layer

b. Data Link Layer

c. Network Layer

d. Transport Layer

e. Session Layer

f. Presentation Layer

g. Application Layer

29. Which layers are network support layers?

a. Physical Layer

b. Data link Layer and 

c. Network Layers

30. Which layers are user support layers?

a. Session Layer

b. Presentation Layer and 

c. Application Layer

31. Which layer links the network support layers and user support layers?

The Transport layer links the network support layers and user support layers.

32. What are the concerns of the Physical Layer?

Physical layer coordinates the functions required to transmit a bit stream over a physical medium.

a. Physical characteristics of interfaces and media

b. Representation of bits

c. Data rate

d. Synchronization of bits

e. Line configuration

f. Physical topology

g. Transmission mode

33. What are the responsibilities of Data Link Layer?

The Data Link Layer transforms the physical layer, a raw transmission facility, to a reliable link and is responsible for node-node delivery.

a. Framing

b. Physical Addressing

c. Flow Control

d. Error Control

e. Access Control

34. What are the responsibilities of Network Layer?

The Network Layer is responsible for the source-to-destination delivery of packet possibly across multiple networks (links).

a. Logical Addressing

b. Routing

35. What are the responsibilities of Transport Layer?

The Transport Layer is responsible for source-to-destination delivery of the entire message.

a. Service-point Addressing

b. Segmentation and reassembly

c. Connection Control

d. Flow Control

e. Error Control

36. What are the responsibilities of Session Layer?

The Session layer is the network dialog Controller. It establishes, maintains and synchronizes the interaction between the communicating systems.

a. Dialog control

b. Synchronization

37. What are the responsibilities of Presentation Layer?

The Presentation layer is concerned with the syntax and semantics of the information exchanged between two systems.
a. Translation
b. Encryption
c. Compression

38. What are the responsibilities of Application Layer?

The Application Layer enables the user, whether human or software, to access the network. It provides user interfaces and support for services such as e-mail, shared database management and other types of distributed information services.
a. Network virtual Terminal
b. File transfer, access and Management (FTAM)
c. Mail services
d. Directory Services

39. What are the two classes of hardware building blocks?

Nodes and Links.

40. What are the different link types used to build a computer network?

a. Cables
b. Leased Lines
c. Last-Mile Links
d. Wireless Links

41. What are the categories of Transmission media?

a. Guided Media
  i. Twisted - Pair cable
    1. Shielded TP
    2. Unshielded TP
  ii. Coaxial Cable
  iii. Fiber-optic cable
b. Unguided Media
  i. Terrestrial microwave
  ii. Satellite Communication

42. What are the types of errors?

a. Single-Bit error
  In a single-bit error, only one bit in the data unit has changed
b. Burst Error
  A Burst error means that two or more bits in the data have changed.

Cisco Router Commands

Routing with Cisco 2500 and 1000 Series for LAN-ISDN Service

Commands - General

There are 3 different modes of operation within the Cisco IOS.

1. Disabled mode
2. Enabled mode
3. Configuration mode

In the Disabled mode you can use a limited number of commands. This is used primarily to monitor the router.

The Enabled mode is used to show configuration information, enter the configuration mode, and make changes to the configuration.

The Configuration mode is used to enter and update the runtime configuration.

To get a list of the commands for the cisco type '?' at the prompt. To get further information about any command, type the command followed by a '?'.

clear	Reset functions
clock	Manage the system clock
configure	Enter configuration mode
debug	Debugging functions (see also 'undebug')
disable	Turn off privileged commands
enable	Turn on privileged commands
erase	Erase flash or configuration memory
exit	Exit from the EXEC
help	Description of the interactive help system
login	Log in as a particular user
logout	Exit from the EXEC
no	Disable debugging functions
ping	Send echo messages
reload	Halt and perform a cold restart
setup	Run the SETUP command facility
show	Show running system information
telnet	Open a telnet connection
terminal	Set terminal line parameters
test	Test subsystems, memory, and interfaces
traceroute	Trace route to destination
tunnel	Open a tunnel connection
undebug	Disable debugging functions (see also 'debug')
verify	Verify checksum of a Flash file
write	Write running configuration to memory, network, or terminal
show
access-lists	List access lists
arp	ARP table
buffers	Buffer pool statistics
configuration	Contents of Non-Volatile memory
controllers	Interface controller status
debugging	State of each debugging option
dialer	Dialer parameters and statistics
extended	Extended Interface Information
flash	System Flash information
flh-log	Flash Load Helper log buffer
history	Display the session command history
hosts	IP domain-name, lookup style, name servers, and host table
interfaces	Interface status and configuration
ip	IP information
isdn	ISDN information
line	TTY line information
logging	Show the contents of logging buffers
memory	Memory statistics
privilege	Show current privilege level
processes	Active process statistics
protocols	Active network routing protocols
queue	Show queue contents
queueing	Show queueing configuration
reload	Scheduled reload information
route-map	route-map information
running-config	Current operating configuration
sessions	Information about Telnet connections
smf	Software MAC filter
stacks	Process stack utilization
startup-config	Contents of startup configuration
subsys	Show subsystem information
tcp	Status of TCP connections
terminal	Display terminal configuration parameters
users	Display information about terminal lines
version	System hardware and software status

Other Useful Commands

View the Software Version
View the Ethernet IP
View the Serial IP
View the Default Route
View the Filters
View the Bandwidth
Add a Static Route
Change the Dial Number
Turn Filters On and Off
Ping from the Router
Traceroute from the Router

View the Ethernet IP

Router#wr term


This will show the running configuration.
Within the configuration, you will see an interface ethernet 0 section:


interface Ethernet0
ip address 38.150.93.1 255.255.255.0
no ip directed-broadcast

View the Serial IP

Router#wr term


Within the configuration, you will see an interface serial 0 section:


interface Serial0
ip address 38.21.10.100 255.255.255.0
ip broadcast-address 38.21.10.255
ip access-group 106 in
encapsulation frame-relay
bandwidth 56
no fair-queue
frame-relay map ip 38.21.10.1 500 IETF

View the Default Route

Router#wr term


Within the configuration, you will see an ip route section. 


In the ip route section, look for a route:
ip route 0.0.0.0 0.0.0.0 38.167.29.1
The last ip address is the POP ip.

View the Filters

Router#wr term


Under interface serial 0, look for:


ip access-group 104 in
ip access-group 105 out


This means that access-group 104 is the inbound filter set and
access-group 105 is the outbound filter set.
Then, continue to look in the configuration for the access-list statements:


(Example access-list statements)
access-list 104 deny   ip 38.166.101.0 0.0.0.255 any
access-list 104 permit tcp any any established
access-list 104 permit tcp any eq ftp-data any gt 1023
access-list 104 permit udp any eq domain any gt 1023
access-list 104 permit udp any eq domain any eq domain
access-list 104 permit icmp any any
access-list 104 permit udp any eq snmp any gt 1023
access-list 105 deny   ip any 38.166.101.0 0.0.0.255
access-list 105 permit tcp any any established
access-list 105 permit tcp any any eq ftp
access-list 105 deny   udp any eq netbios-ns any
access-list 105 deny   udp any eq netbios-dgm any
access-list 105 permit ip any any

View the Bandwidth

Router#wr term


Within the config, you will see an interface serial 0 section:


interface Serial0
ip address 38.21.10.100 255.255.255.0
ip broadcast-address 38.21.10.255
ip access-group 106 in
encapsulation frame-relay
bandwidth 56
no fair-queue
frame-relay map ip 38.21.10.1 500 IETF

Add a Static Route

Cisco#config t
Enter configuration commands, one per line.  End with CNTL/Z.
Cisco(config)#ip route DEST.DEST.DEST.DEST MASK.MASK.MASK.MASK GATE.GATE.GATE.GATE
where: DEST.DEST.DEST.DEST = The destination network the static route is for
       MASK.MASK.MASK.MASK = The subnet mask of the destination network
       GATE.GATE.GATE.GATE = The gateway of the static route
Example route statement:
ip route 38.222.75.0 255.255.255.0 38.20.5.1
Cisco(config)#^Z (hit  z)


Write the entry to memory:


Cisco#wr mem
Building configuration...
[OK]

Change the Dial Number

Type en to put the router in enable mode:


test.com>en


The password should be the same as the one used to telnet in.


Password:


To view the router's configuration, type:


test.com#show config


There will be a line in the configuration that says:


dialer map IP 38.1.1.1 speed 64 name LD3330 2707000


The 2707000 is the dial number.


NOTE: Record what interface the dialer map IP line is under because     you will need to  use that interface when changing the number.


Type config t to configure from terminal.


test.com#config t


Enter configuration commands, one per line.  End with CNTL/Z.
Enter the interface that the dialer map IP line is under:


test.com(config)#interface BRI0


Add in the new dialer map IP line with the new phone number:


test.com(config)#dialer map IP 38.1.1.1 speed 64 name LD3330 [new number]


Now, remove the old dialer map IP line.
To remove a line, type no and then the line.
For example, to remove the old dialer map IP, type:


test.com(config)#no dialer map IP 38.1.1.1 speed 64 name LD3330 2707020


Now leave config mode:


test.com(config)# [control] z


Save changes:


test.com# write mem
Building configuration...
[OK]


Verify the new number is in the config:


test.com#show config


The new number should be in the dialer map IP line.

Turn Filters On and Off

To turn the filters off:


Router#configure terminal
Router(config)#interface Serial0
Router(config-if)#no ip access-group 104 in
Router(config-if)#no ip access-group 105 out
Router(config-if)# Hit CTRL-Z
Router#wr mem
Building configuration...
[OK]
Router#


To turn the filters on:


Router#configure terminal
Router(config)#interface Serial0
Router(config-if)#ip access-group 104 in
Router(config-if)#ip access-group 105 out
Router(config-if)# Hit CTRL-Z
Router#wr mem
Building configuration...
[OK]
Router#

Ping from the Router

Cisco#ping 
Example:
Cisco#ping 38.8.14.2