Networking interview questions - posted on June 27, 2013 at
16:45 PM by Kshipra Singh
1. Differentiate between hub and switch.
a.) Hub is a layer 1 device while Switch is layer 2 device.
b.) Hub works on single collision and single broadcast domain while switch
works on per port collision and single broadcast domain.
2. What is FQDN?
- FQDN is the abbreviation for Fully Qualified Domain Name.
- It contains both the hostname and a domain name.
- It uniquely identifies a host within a DNS hierarchy
3. Tell us something about LMHOSTS files.
- It is a text file that resolves NetBIOS names to IP addresses.
- It can be compared with the HOSTS file which is a static method of resolving
domain names into IP addresses.
- LMHOSTS files must be manually configured and updated.
4. What are the main qualities of an effective and efficient network?
5. What are 10Base2, 10Base5 and 10BaseT Ethernet LANs?
- It is an Ethernet term which means a maximum transfer rate of 10 Megabits per
second that uses baseband signaling, with a contiguous cable segment length of
100 meters and a maximum of 2 segments.
- It is an Ethernet term meaning a maximum transfer rate of 10 Megabits per
second that uses baseband signaling, with 5 continuous segments not exceeding
100 meters per segment.
- It is an Ethernet term meaning a maximum transfer rate of 10 Megabits per
second that uses baseband signaling and twisted pair cabling.
6. What is anonymous FTP? What is its use?
- It is an FTP that enables the users to connect to a host without a valid login
- The login used is anonymous or guest, with the password usually requesting
the user's ID.
- It enables a large number of users to access the files on the host without
needing to set up a login for all of them.
- It exercises a strict control over the areas an anonymous user can access.
7. Which factors mark the reliability of the network?
a. Frequency of failure
b. Downtime / Time taken for recovery.
8. Name the factors that tell us about the security of the network.
a. Virus attacks on the system.
b. Unauthorized access to the system.
9. Define Bandwidth and Latency?
- Bandwidth/ Throughput – It means the number of bits which can be transmitted
over the network in a specified time.
- Latency – It is the time taken by a message to travel from one side to
Bandwidth and latency describe the performance of a network.
10. What is point to point link?
- Direct connection between two computers on a network is called as point to
- No other network devices other than a connecting cable are required for point
to point connection.
- The cable connects the NIC card of both the devices.
11. When is a switch said to be congested?
- Sometimes a switch receives the packets faster than they can be accommodated
in the shared link. These packets are stored in the memory for sometime.
- However, after sometime the buffer space will exhaust and some packets will
start getting dropped off.
- The switch is called as congested in this state.
12. Explain a.) Uni-casting, b.) Multicasting and c.) Broadcasting
a.) Uni-casting - Message is sent from a source to a single destination node.
b.) Multicasting - Message is sent from a source to some subsets of other
c.) Broadcasting - Message is sent from a source to all the nodes in the
13. What are the various types of Multiplexing?
The various types of multiplexing are:
a. Frequency Division Multiplexing (FDM)
b. Time Division Multiplexing (TDM)
i. Synchronous TDM
ii. Asynchronous TDM
c. Wave Division Multiplexing (WDM)
14. Which layers of OSI are referred to as network support layers?
The following 3 layers of OSI are referred to as network support layers:
a. Physical Layer
b. Data link Layer and
c. Network Layers
15. Which layers of OSI are referred to as user support layers?
The block of user support layers consists of:
a. Session Layer
b. Presentation Layer and
c. Application Layer
16. What does the Data Link Layer do?
- The Data Link Layer transforms the physical layer to a reliable link.
It takes care of:
a. Node to node delivery.
c. Physical Addressing
d. Flow Control
e. Error Control
f. Access Control
17. What is NIC?
- NIC stands for Network Interface Card.
- It is a peripheral card attached to a PC to helps it connect to a network.
- The MAC address of the card helps the network in identifying the PC.
18. What are the responsibilities of Network Layer?
- The Network Layer aids in source-to-destination delivery of packet across
- It performs:
a. Logical Addressing
19. Name the various error detection methods.
The various error detection methods are:
a. Vertical Redundancy Check (VRC)
b. Longitudinal Redundancy Check (VRC)
c. Cyclic Redundancy Check (VRC)
20. . What is Bit Stuffing?
- Bit stuffing means adding one extra 0 whenever five consecutive 1s follow a 0.
- This is done so that the pattern 0111110 is not mistaken for a flag.
21. How does dynamic host configuration protocol aid in network administration?
- In a large set up where it is difficult to manually configure the IP address
of each system, dynamic host configuration protocol comes very helpful.
- Using this protocol, the administrator can create a pool of IP addresses
which are called scopes. These can be then dynamically assigned to the systems.
Brute forcing is a mechanism which is used by an attacker to break the
encryption of data by applying a set of various key.............
RSA is a public key encryption algorithm. The RSA algorithms are...........
Encoding: Basically encoding is used to protect the integrity of data as it
crosses through communication network to keep its original message.............
A secure hash function should have the following
A digital signature is an electronic analogue of a written signature; the
digital signature can be used to provide assurance...........
Basically Authentication Header protects IP header and provides the complete
authenticity to the IP packets.............
The SSL protocol (Secure Socket Layer protocol) was originally developed by
Netscape, to ensure security of data transported.............
PIX (Private Internet Exchange)...........
Malware is a software program which is developed to destroy a computer
Replay attacks are the network attacks in which an attacker spies the
conversation between the sender and receiver..........
Data should be transmitted over any communication network in such a way that the
data integrity and authenticity.............
Mainly there are three Information security goals in an organization:
Confidentiality, Integrity and Availability..............
Symmetric-Key Cryptography: Symmetric-key cryptography uses a single key for
both encryption and decryption. Encryption and decryption algorithm are inverse
of each other.............
Latest answer: Addressing: For the purpose of delivering
datagram packets, IP needs to know about the address of the destination. By
including the host addressing, this task is carried out by IP. As IP operates
in an internet, its systems are designed to accept the addressing of devices
which are unique.............
the classes of IP address
Latest answer: IP addresses are organized into classes. For
convenience of humans, IP addresses are expressed in the decimal format. Every
number in each class is represented as binary to computers..................
Broadcast, Unicast and Multicast.
Latest answer: Unicast: A term used in communication to
describe a piece of information to send from one point to another. There are
only sender and receiver................
is Network Mask?
Latest answer: A network mask is used for determination of what
subnet an IP address belongs to. An IP address has network address and the host
Latest answer: A subnet describes a set of networked computers
which have common IP address routing prefix..................
is the User Datagram Protocol (UDP)?
Latest answer: User datagram protocol allows computer
applications to send messages as datagram packets from source to destination on
an Internet Protocol,..................
TCP Windowing concept.
Latest answer: TCP Windowing is a concept that is used for
avoiding congestion in the network traffic..................
is the Domain Name System (DNS)? What are the advantages of it?
Latest answer: A hierarchical naming system for computer
systems, services or for that matter any resource participating in the
is the TTL (Time to Live)? Why is it required?
Latest answer: TTL is a value in data packet of Internet
Protocol. It communicates to the network router whether or not the packet
should be in the network for too long or discarded.................
the use of Internet Control Message Protocol (ICMP)
Latest answer: Internet Control Message Protocol is one of the
important protocols in the Internet Protocol suite. It is mainly used in
operating system of networked computers..................
Latest answer: Internet Group Management Protocol: - It allows
internet hosts to participate in multicasting. The IGMP messages are used to
learn which hosts is part of which multicast groups..............
Latest answer: Ping and tracert are the commands used to send
information to some remote computers to receive some information. Information
is sent and received by packets..............
Latest answer: Resource Reservation protocol is used to reserve
resources across a network. It is used for requesting a specific Quality of
Service (QoS) from the network...............
Latest answer: Dynamic Host Configuration Protocol is used
assigning IP addresses to computers in a network. The IP addresses are assigned
Latest answer: In a domain, one or more computer can be a
server to manage the network. On the other hand in a workgroup all computers
are peers having no control on each other.............
Latest answer: Network Address Translation translates and IP
address used in a network to another IP address known within another network. A
NAT table is maintained for global to local and local to mapping of
Latest answer: Point to Point protocol helps communication
between 2 computers over a serial cable, phone line or other fiber optic lines.
E.g. Connection between an Internet Service Provider and a host................
Latest answer: IP spoofing is a mechanism used by attackers to
gain unauthorized access to a system. Here, the intruder sends messages to a
computer with an IP address indicating that the message is coming from a
Latest answer: IP datagram can be used to describe a portion of
IP data. Each IP datagram has set of fields arranged in an order. The order is
specific which helps to decode and read the stream easily..............
Latest answer: An application gateway is an application program
that runs on a firewall between two networks. An application gateway is used
for establishing connection between client program and destination
Latest answer: A circuit level gateway is used to find if a
session in TCP handshaking is legitimate or not. It can be considered as a
layer between application layer and transport layer..................
A Gateway of Last Resort or Default gateway is a route used by the router when
no other known route exists to transmit the IP packet. Known routes are present
in the routing table.................
Latest answer: It is a device that connects multiple network
A switch analyzes the MAC address and then determines where to send the
Latest answer: The way switches connect multiple computers, a
router connects multiple networks. Routers comprise of data consisting of large
tables of networks and addresses..................
Latest answer: OSI stands for Open Systems Interconnection
The OSI reference model gives an overview of the layered communications and
computer network protocol design...................
Latest answer: Application Layer: Closest to the end user,
Interact directly with the software application.
Presentation Layer: Translates application to network format, and vice versa,
Works to transform data into the form that the application layer can accept,
Formats and encrypts data to be sent across a network.........................
Latest answer: It is an IP address that uniquely identifies a
host in a network.
The datagram with a unicast IP address is received and processed by only a
Latest answer: It is an IP address that identifies a particular
group of hosts in network.
This group of hosts is called a multicast group..............
Latest answer: Class A:
Range: from 0.0.0.0 to 127.255.255.255.
Leftmost bit: 0.
First 8 bits: netid.
Remaining 24 bits: hostid..............
Latest answer: Subneting is dividing a network into several
This is usually done for the following purposes:..................
Latest answer: Supernetting or Classless Inter-Domain Routing
(CIDR) : It is a way to aggregate multiple Internet addresses of the same
Latest answer: VLSM is a means of allocating IP addressing
resources to subnets according to their individual need rather than some
general network-wide rule................
Latest answer: Fragmentation occurs when storage space is used
inefficiently due to which storage capacity and performance is
Latest answer: Data transmitted over an internet using IP is
carried in messages called IP datagrams. Like all network protocol messages, IP
uses a specific format for its datagrams...................
Media Access Control address is an identifier for assigned to most network
adapters or Network Interface Cards by the manufacturer for the purpose of
Describe the Packet Format of ARP (Address Resolution Protocol)?
The fields of the packet format of ARP are as follows:
-Hardware type: It is a 16-bit field . Each LAN has been assigned an integer
based on its type. For example, Ethernet is given the type 1.
-Protocol type: This is a 16-bit field defining the protocol. For example, the
value of this field for IPv4 protocol is 0800.
-Hardware length: This is an 8-bit field defining the length of the physical
address in bytes. For example, for Ethernet the value is 6.
-Protocol length: This is an 8-bit field defining the length of the logical
address in bytes. For example, for IPv4 protocol the value is 4.
-Operation: This is a 16-bitfield defining the type of packet. Two packet types
are defined: ARP request (1), ARP reply (2).
-Sender hardware address: This is a variable-length field defining the physical
address of the sender. For example, for Ethernet this field is 6 bytes long.
-Sender protocol address: This is a variable-length field defining the logical
(for example, IP) address of the sender. For the IP protocol, this field is 4
-Target hardware address: This is a variable-length field defining the physical
address of the target. For example, for Ethernet this field is 6 bytes long.
-Target protocol address: This is a variable-length field defining the logical
(for example, IP) address of the target. For IPv4 protocol, this field is 4
What are the advantages of IPv6 over IPv4?
the next generation IP, or IPv6 has some advantages over IPv4 that can be
summarized as follows:
- Larger Address Space: An IPv6 address is 128 bytes long where IPv4 has 32-bit
address only, this is a huge increase in the address space.
- Better Header Format: IPv6 uses a new header format which simplifies and
speeds up the routing process because most of the options do not need to be
checked by routers.
- New Options: IPv6 has new options to allow for additional functionalities.
- Allowance for extension: In IPv6 new technologies can easily embedded.
-Support For Resource Allocation: In IPv6, flow label has been added to enable
the source to request special handling of the packet. This mechanism can be
used to support traffic such as real-time audio and video.
-Support For More Security: The encryption and authentication options in IPv6
provide confidentiality and integrity of the packet.
What are the different design goals of ATM?
Asynchronous Transfer Mode (ATM) is the cell relay protocol.
The Design Goals of ATM are as follows:
- A technology is needed to take advantage of high rate transmission media and
less susceptible to noise degradation for maximizing the data rates.
-The system must interface with existing systems and provide wide-area
-The implementation of design must be cheaper enough so that everyone can
afford it. If ATM is to become the backbone of international communications, as
indeed, it must be available at low cost to every user who wants it.
-The new system must be able to work with and support the existing
- The new system must be connection-oriented to ensure accurate and predictable
- One objective is to move as many of the functions to hardware as possible
(for speed) an eliminate as many software functions as possible (again for
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