Networking Interviews

This article includes top 100 networking interview questions with answers. These are the most frequently asked interview questions in computer networking field for the entry level job.

Top 100 Networking Interview Questions with Answers

What is difference between packet switch and circuit switch network?

To make a baseband network practical for many computers to share, the data transmitted by each system is broken up into separate units called packets. When your computer transmits data it might be broken up into many packets, and the computer transmits each packet separately. When all of the packets constituting a particular transmission reach their destination, the receiving computer reassembles them back into original data. This is the basis for a packet-switching network.

Circuit-switching means that the two systems wanting to communicate establish a circuit before they transmit any information. That circuit remains open throughout the life of the exchange, and is only broken when the two systems are finished communicating. Circuit switching is more common in environments like the public switched telephone network (PSTN), in which the connection between your telephone and that of the person you're calling remains open for the entire duration of the call.

What is difference between Half-Duplex and Full-Duplex Communications?

In half-duplex communication data travels in only one direction at a time.

In full-duplex mode two systems that can communicate in both directions simultaneously are operating.

Which is the most popular international cable standard?

TIA/EIA-568-B

Describe UTP cable

UTP cable comes in a variety of different grades, called "categories" by the Electronics Industry Association (EIA) and the Telecommunications Industry Association (TIA), the combination being referred to as EIA/TIA.

  • Cat 1 :- Used for voice-grade telephone networks only; not for data transmissions
  • Cat 2 :- Used for voice-grade telephone networks
  • Cat 3 :-Used for voice-grade telephone networks, 10 Mbps Ethernet, 4 Mbps Token Ring,
  • Cat 4 :-Used for 16 Mbps Token Ring networks
  • Cat 5 :-Used for 100BaseTX Fast Ethernet, SONet, and OC-3 ATM
  • Cat 5e:- Used for Gigabit (1000 Mbps) Ethernet protocols

What is TIA/EIA?

A cooperative trade association responsible for the "Commercial Building Telecommunication Cabling Standard," also known as EIA/TIA 568, which specifies how network cables should be installed in a commercial site.

What is attenuation ?

The progressive weakening of a signal as it travels over a cable or other medium. The longer the distance a signal travels, the weaker the signal gets, until it becomes unreadable by the receiving system

What is Crosstalk ?

A type of signal interference caused by signals transmitted on one pair of wires bleeding over into the other pairs. Crosstalk can cause network signals to degrade, eventually rendering them unviable.

Where would you use cross and straight cable?

A straight-through cable is used for DTE-to-DCE connections.

  • 1. A hub to a router, PC, or file server
  • 2.A switch to a router, PC, or file server

Crossover cables should by used when you connect a DTE to another DTE or a DCE to another DCE.

  • 1. A hub to another hub
  • 2. A switch to another switch
  • 3. A hub to a switch
  • 4. A PC, router, or file server to another PC, router, or file server

Describe different types of connector used in LAN

RJ-11 ( Registered Jack-11) a four- or six-wire connector primarily used to connect telephone equipment.

RJ-45 (Registered Jack-45) connector is an eight-wire connector that is commonly used to connect computers to a local area network (LAN), particularly Ethernet LANs.

AUI( Attachment Unit Interface.) is the part of the Ethernet standard that specifies how a Thicknet cable is to be connected to an Ethernet card. AUI specifies a coaxial cable connected to a transceiver that plugs into a 15-pin socket on the network interface card (NIC).

BNC stand for British Naval Connector (or Bayonet Nut Connector or Bayonet Neill Concelman)a type of connector used with coaxial cables such as RG-58.BNC connectors are used on both Thicknet and Thinnet.

What is protocol?

A set of standards that define all operations within a network. There are various protocols that operate at various levels of the OSI network model such as transport protocols include TCP.

Who develop the OSI modal?

The International Organization for Standardization (ISO) developed the Open Systems Interconnection (OSI) Reference Model to describe how information is transferred from one machine to another.

What is Micro segmentation?

Micro segmentation is a term used with switches when each networking device has its own dedicated port on a switch.

What are the advantages of OSI modal?

  • Defines the process for connecting two layers, promoting interoperability between vendors.
  • Separates a complex function into simpler components.
  • Allows vendors to compartmentalize their design efforts to fit a modular design, which eases implementations and simplifies troubleshooting

What are the port number / socket number and Connection Multiplexing?

Transport layer assigns a unique set of numbers for each connection. These numbers are called port or socket numbers TCP, and UDP, provide a multiplexing function for a device: This allows multiple applications to simultaneously send and receive data.

Lan Card Test Sheet

Also know as Ethernet Card, or NIC Network interface card.
In device manage Reason In LAN card properties
Yellow sign Driver not installed Will not show
Red Cross Disable Show with disable status
No Ethernet option Physical not installed Will not show

At Command Prompt

C:/> ipconfig
Possible out put
IP address of computer Everything is fine
Windows ip Configuration Either media is disconnected or LAN disable
C:/> ping <Remote computer ip>
Used to check the physical connectivity
Possible out put
Reply From ..... Host is up and operational
Request time out Either firewall is on remote desktop or network plug is loose
Destination net unreachable There is no route to reach to the remote network

What is remote desktop?

A feature that's allow user to manage computers remotely.
On server side
My computer ==> properties ==> remote ==> Tick mark on this check box allow user to connect this computer remotely ==> select user.
On client
start ==> program ==> accessories ==> communication ==> remote desktop ==> Server ip ==> user name and password configured on server.
Role of server side can be played only by XP professional or server2003.

How will you make dial-up connection ?

Physical installation of modem ==> install modem driver ==> my network place ==> properties ==> Make new connection ==> next ==>connection to internet ==> setup my connection manually ==> Connect using a dial up modem

How will you share printer ?

Install local printer on that pc which has physically attached printer. And then Right click on it ==> share ==> In xp if you run small office set wizard it will be share automatically. On all other PC install network printer. While installing printer choose network printer.

How will you configure broadband ?

There are two type of broadband available

One that required user name and password to connect the internet like BSNL or Reliance for this type of connection Physical installation of modem ==> my network place ==> properties ==> Make new connection ==> next ==> connection to internet ==> setup my connection manually ==> Connect using a broadband connection that requires a user name and password ==> ISP name ==> User name and password ==> add a short cut to desktop
If you are using other type of connection like Airtel for this type of connection you don't required any additional configuration
If DHCP is enable in modem
IP address and DNS setting will be automatically configure.
If DHCP is not enable then set it manually as given ip by provider

What is minimum requirement of RAM for installation of XP?

64 MB

What is firewall?

The primary method for keeping a computer secure from unauthorized user. A firewall allows or blocks traffic into and out of a private network or the user's computer. Firewalls are widely used to give users secure access to the Internet as well as to separate a company's public Web server from its internal network.
XP pack 2 has a built in firewall that is enabled by default. To change the setting of it use this path
Local area network ==> properties ==> advance ==> setting

What is Active Directory?

Active Directory is a network-based object store and service that locates and manages resources, and makes these resources available to authorized users and groups. An underlying principle of the Active Directory is that everything is considered an object—people, servers, workstations, printers, documents, and devices. Each object has certain attributes and its own security access control list (ACL).

Workers are not able to print from the printer, there user logon are correct and are allowed to print from that printer in active directory. How would you resolve this issue?

  1. Verify printer is set as default.
  2. Verify users have local privileges set properly to print.
  3. Is print server delivering correct drivers.
  4. Is local naming convention for printer correct.
  5. If pre Win2000 workstation, naming convention must be less than 12 characters.
  6. Make sure no viruses present. Some Viruses can shut down IPC shares and printing services.

Where are the Windows NT Primary Domain Controller (PDC) and its Backup Domain Controller (BDC) in Server 2003?

The scheme of PDC and BDC is replaced by The Active Directory in server 2000 and further. Now all domain controllers share a multi master peer-to-peer read and write relationship that hosts copies of the Active Directory.

How can group policy be refreshed?

  1. Restart the server
  2. Leave the server ideal for 90 minute
  3. Run ==> gpupdate (server 2003 only)

What is LILO?

LILO stands for Linux boot loader. It will load the MBR, master boot record, into the memory, and tell the system which partition and hard drive to boot from.

I can't seem to access the Internet, don't have any access to the corporate network and on IP configuration on my address is 169.254.*.*. What happened?

The 169.254.*.* net mask is assigned to Windows machines running 98/2000/XP if the DHCP server is not available. The name for the technology is APIPA (Automatic Private Internet Protocol Addressing).

We've installed a new Windows-based DHCP server, however, the users do not seem to be getting DHCP leases off of it.

The server must be authorized first with the Active Directory.

What's the difference between local, global and universal groups?

Domain local groups assign access permissions to domain groups for local domain resources. Global groups provide access to resources in entire domains.

What's the major difference between FAT and NTFS on a local machine?

FAT and FAT32 provide no security over locally logged-on users. Only native NTFS provides extensive permission control on both remote and local files.

What is presentation layer and how it is responsible for in the OSI model?

The presentation layer establishes the data format prior to passing it along to the network application's interface. TCP/IP networks perform this task at the application layer

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 192.16.8.0.0 192.168.255.255

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