100 Networking Interview Questions
Q1. What are 10Base2,
10Base5 and 10BaseT Ethernet LANs?
Ans. 10Base2—An Ethernet term meaning 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.
10Base5—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.
10BaseT—An Ethernet term meaning a maximum transfer rate of 10 Megabits per
second that uses baseband signaling and twisted pair cabling.
Q2. What is the difference between an unspecified passive open and a fully
specified passive open?
Ans. An unspecified passive open has the server waiting for a connection
request from a client. A fully specified passive open has the server waiting
for a connection from a specific client.
Q3. Explain the
function of Transmission Control Block.
Ans. A TCB is a complex data structure that contains a considerable amount of
information about each connection.
Q4. What is a
Management Information Base (MIB)?
Ans. A Management Information Base is part of every SNMP-managed device. Each
SNMP agent has the MIB database that contains information about the device’s
status, its performance, connections, and configuration. The MIB is queried by
SNMP.
Q5. What is anonymous
FTP and why would you use it?
Ans. Anonymous FTP enables users to connect to a host without using a valid
login and password. Usually, anonymous FTP uses a login called anonymous or
guest, with the password usually requesting the user’s ID for tracking purposes
only. Anonymous FTP is used to enable a large number of users to access files
on the host without having to go to the trouble of setting up logins for them
all. Anonymous FTP systems usually have strict controls over the areas an
anonymous user can access.
Q6. What is a pseudo
tty?
Ans. A pseudo tty or false terminal enables external machines to connect
through Telnet or rlogin. Without a pseudo tty, no connection can take place.
Q7. Which layer of the
7 layer model provides services to the Application layer over the Session layer
connection?
Ans. Presentation.
Q8. What does the
Mount protocol do ?
Ans. The Mount protocol returns a file handle and the name of the file system
in which a requested file resides. The message is sent to the client from the
server after reception of a client’s request.
Q9. What is External
Data Representation?
Ans. External Data Representation is a method of encoding data within an RPC
message, used to ensure that the data is not system-dependent.
Q10. Which OSI
Reference Layer controls application to application communication?
Ans. Session
Q11. BOOTP helps a
diskless workstation boot. How does it get a message to the network looking for
its IP address and the location of its operating system boot files ?
Ans. BOOTP sends a UDP message with a subnetwork broadcast address and waits
for a reply from a server that gives it the IP address. The same message might
contain the name of the machine that has the boot files on it. If the boot
image location is not specified, the workstation sends another UDP message to
query the server.
Q12. What is a DNS
resource record?
Ans. A resource record is an entry in a name server’s database. There are
several types of resource records used, including name-to-address resolution
information. Resource records are maintained as ASCII files.
Q13. What protocol is
used by DNS name servers?
Ans. DNS uses UDP for communication between servers. It is a better choice than
TCP because of the improved speed a connectionless protocol offers. Of course,
transmission reliability suffers with UDP.
Q14. What is the
difference between interior and exterior neighbor gateways?
Ans. Interior gateways connect LANs of one organization, whereas exterior
gateways connect the organization to the outside world.
Q15. What is the HELLO
protocol used for?
Ans. The HELLO protocol uses time instead of distance to determine optimal
routing. It is an alternative to the Routing Information Protocol.
Q16. What are the
advantages and disadvantages of the three types of routing tables?
Ans. The three types of routing tables are fixed, dynamic, and fixed central.
The fixed table must be manually modified every time there is a change. A
dynamic table changes its information based on network traffic, reducing the
amount of manual maintenance. A fixed central table lets a manager modify only
one table, which is then read by other devices. The fixed central table reduces
the need to update each machine’s table, as with the fixed table. Usually a
dynamic table causes the fewest problems for a network administrator, although
the table’s contents can change without the administrator being aware of the
change.
Q17. What is a
characteristic of Store and Forward switches?
Ans. They read the entire frame and check CRC before forwarding.
Q18. What is source
route?
Ans. It is a sequence of IP addresses identifying the route a datagram must
follow. A source route may optionally be included in an IP datagram header.
Q19. What is RIP
(Routing Information Protocol)?
Ans. It is a simple protocol used to exchange information between the routers.
Q20. What is SLIP
(Serial Line Interface Protocol)?
Ans. It is a very simple protocol used for transmission of IP datagrams across
a serial line.
Q21. What is Proxy
ARP?
Ans. It is using a router to answer ARP requests. This will be done when the
originating host believes that a destination is local, when in fact is lies
beyond router.
Q22. What is OSPF?
Ans. It is an Internet routing protocol that scales well, can route traffic
along multiple paths, and uses knowledge of an Internet’s topology to make
accurate routing decisions.
Q23. What is Kerberos?
Ans. It is an authentication service developed at the Massachusetts Institute
of Technology. Kerberos uses encryption to prevent intruders from discovering
passwords and gaining unauthorized access to files.
Q24. What is a
Multi-homed Host?
Ans. It is a host that has a multiple network interfaces and that requires
multiple IP addresses is called as a Multi-homed Host.
Q25. What is NVT
(Network Virtual Terminal)?
Ans. It is a set of rules defining a very simple virtual terminal interaction.
The NVT is used in the start of a Telnet session.
Q26. What is
Gateway-to-Gateway protocol?
Ans. It is a protocol formerly
used to exchange routing information between Internet core routers.
Q27. What is BGP
(Border Gateway Protocol)?
Ans. It is a protocol used to advertise the set of networks that can be reached
with in an autonomous system. BGP enables this information to be shared with
the autonomous system. This is newer than EGP (Exterior Gateway Protocol).
Q28. What is
autonomous system?
Ans. It is a collection of routers under the control of a single administrative
authority and that uses a common Interior Gateway Protocol.
Q29. What is EGP (Exterior
Gateway Protocol)?
Ans. It is the protocol the routers in neighboring autonomous systems use to
identify the set of networks that can be reached within or via each autonomous
system.
Q30. What is IGP
(Interior Gateway Protocol)?
Ans. It is any routing protocol used within an autonomous system.
Q31. What is Mail
Gateway?
Ans. It is a system that performs a protocol translation between different
electronic mail delivery protocols.
Q32. What is
wide-mouth frog?
Ans. Wide-mouth frog is the simplest known key distribution center (KDC)
authentication protocol.
Q33. What are Digrams
and Trigrams?
Ans. The most common two letter combinations are called as digrams. e.g. th,
in, er, re and an. The most common three letter combinations are called as
trigrams. e.g. the, ing, and, and ion.
Q34. What is silly
window syndrome?
Ans. It is a problem that can ruin TCP performance. This problem occurs when
data are passed to the sending TCP entity in large blocks, but an interactive
application on the receiving side reads 1 byte at a time.
Q35. What is region?
Ans. When hierarchical routing is used, the routers are divided into what we
call regions, with each router knowing all the details about how to route
packets to destinations within its own region, but knowing nothing about the
internal structure of other regions.
Q36. What is multicast
routing?
Ans. Sending a message to a group is called multicasting, and its routing
algorithm is called multicast routing.
Q37. What is traffic
shaping?
Ans. One of the main causes of congestion is that traffic is often busy. If
hosts could be made to transmit at a uniform rate,congestion would be less
common. Another open loop method to help manage congestion is forcing the
packet to be transmitted at a more predictable rate. This is called traffic
shaping.
Q38. What is packet
filter?
Ans. Packet filter is a standard router equipped with some extra functionality.
The extra functionality allows every incoming or outgoing packet to be
inspected. Packets meeting some criterion are forwarded normally. Those that
fail the test are dropped.
Q39. What is virtual
path?
Ans. Along any transmission path from a given source to a given destination, a
group of virtual circuits can be grouped together into what is called path.
Q40. What is virtual channel?
Ans. Virtual channel is normally a connection from one source to one
destination, although multicast connections are also permitted. The other name
for virtual channel is virtual circuit.
Q41. What is logical
link control?
Ans. One of two sublayers of the data link layer of OSI reference model, as
defined by the IEEE 802 standard. This sublayer is responsible for maintaining
the link between computers when they are sending data across the physical
network connection.
Q42. Why should you
care about the OSI Reference Model?
Ans. It provides a framework for discussing network operations and design.
Q43. What is the difference between routable and non- routable protocols?
Ans. Routable protocols can work with a router and can be used to build large
networks. Non-Routable protocols are designed to work on small, local networks
and cannot be used with a router.
Q44. What is MAU?
Ans. In token Ring , hub is called Multistation Access Unit(MAU).
Q45. Explain 5-4-3
rule?
Ans. In a Ethernet network, between any two points on the network, there can be
no more than five network segments or four repeaters, and of those five
segments only three of segments can be populated.
Q46. What is the
difference between TFTP and FTP application layer protocols?
Ans. The Trivial File Transfer Protocol (TFTP) allows a local host to obtain
files from a remote host but does not provide reliability or security. It uses
the fundamental packet delivery services offered by UDP. The File Transfer
Protocol (FTP) is the standard mechanism provided by TCP / IP for copying a
file from one host to another. It uses the services offered by TCP and so is
reliable and secure. It establishes two connections (virtual circuits) between
the hosts, one for data transfer and another for control information.
Q47. What is the range
of addresses in the classes of internet addresses?
Ans. Class A 0.0.0.0 – 127.255.255.255
Class B 128.0.0.0 – 191.255.255.255
Class C 192.0.0.0 – 223.255.255.255
Class D 224.0.0.0 – 239.255.255.255
Class E 240.0.0.0 – 247.255.255.255
Q48. What is the
minimum and maximum length of the header in the TCP segment and IP datagram?
Ans. The header should have a minimum length of 20 bytes and can have a maximum
length of 60 bytes.
Q49. What is
difference between ARP and RARP?
Ans. The address resolution protocol (ARP) is used to associate the 32 bit IP
address with the 48 bit physical address, used by a host or a router to find
the physical address of another host on its network by sending a ARP query
packet that includes the IP address of the receiver. The reverse address
resolution protocol (RARP) allows a host to discover its Internet address when
it knows only its physical address.
Q50. What is ICMP?
Ans. ICMP is Internet Control Message Protocol, a network layer protocol of the
TCP/IP suite used by hosts and gateways to send notification of datagram
problems back to the sender. It uses the echo test / reply to test whether a
destination is reachable and responding. It also handles both control and error
messages.
100 Networking Questions (part2)
Q51. What are the data
units at different layers of the TCP / IP protocol suite?
Ans. The data unit created at the application layer is called a message, at the
transport layer the data unit created is called either a segment or an user
datagram, at the network layer the data unit created is called the datagram, at
the data link layer the datagram is encapsulated in to a frame and finally
transmitted as signals along the transmission media.
Q52. What is Project
802?
Ans. It is a project started by IEEE to set standards that enable
intercommunication between equipment from a variety of manufacturers. It is a
way for specifying functions of the physical layer, the data link layer and to
some extent the network layer to allow for interconnectivity of major LAN
protocols.
It consists of the following:
·
802.1 is an
internetworking standard for compatibility of different LANs and MANs across
protocols.
·
802.2 Logical link
control (LLC) is the upper sublayer of the data link layer which is
non-architecture-specific, that is remains the same for all IEEE-defined LANs.
·
Media access control
(MAC) is the lower sublayer of the data link layer that contains some distinct
modules each carrying proprietary information specific to the LAN product being
used. The modules are Ethernet LAN (802.3), Token ring LAN (802.4), Token bus
LAN (802.5).
·
802.6 is distributed
queue dual bus (DQDB) designed to be used in MANs.
Q53. What is
Bandwidth?
Ans. Every line has an upper limit and a lower limit on the frequency of
signals it can carry. This limited range is called the bandwidth.
Q54. Difference
between bit rate and baud rate.
Ans. Bit rate is the number of bits transmitted during one second whereas baud
rate refers to the number of signal units per second that are required to
represent those bits.
baud rate = bit rate / N where N is no-of-bits represented by each signal shift.
Q55. What is MAC
address?
Ans. The address for a device as it is identified at the Media Access Control
(MAC) layer in the network architecture. MAC address is usually stored in ROM
on the network adapter card and is unique.
Q56. What is attenuation?
Ans. The degeneration of a signal over distance on a network cable is called
attenuation.
Q57. What is cladding?
Ans. A layer of a glass surrounding the center fiber of glass inside a
fiber-optic cable.
Q58. What is RAID?
Ans. A method for providing fault tolerance by using multiple hard disk drives.
Q59. What is NETBIOS
and NETBEUI?
Ans. NETBIOS is a programming interface that allows I/O requests to be sent to
and received from a remote computer and it hides the networking hardware from
applications.
NETBEUI is NetBIOS extended user interface. A transport protocol designed by
microsoft and IBM for the use on small subnets.
Q60. What is
redirector?
Ans. Redirector is software that intercepts file or prints I/O requests and
translates them into network requests. This comes under presentation layer.
Q61. What is
Beaconing?
Ans. The process that allows a network to self-repair networks problems. The
stations on the network notify the other stations on the ring when they are not
receiving the transmissions. Beaconing is used in Token ring and FDDI networks.
Q62. What is terminal
emulation, in which layer it comes?
Ans. Telnet is also called as terminal emulation. It belongs to application
layer.
Q63. What is frame
relay, in which layer it comes?
Ans. Frame relay is a packet switching technology. It will operate in the data
link layer.
Q64. What do you meant
by “triple X” in Networks?
Ans. The function of PAD (Packet Assembler Disassembler) is described in a
document known as X.3. The standard protocol has been defined between the
terminal and the PAD, called X.28; another standard protocol exists between hte
PAD and the network, called X.29. Together, these three recommendations are
often called “triple X”
Q65. What is SAP?
Ans. Series of interface points that allow other computers to communicate with
the other layers of network protocol stack.
Q66. What is subnet?
Ans. A generic term for section of a large networks usually separated by a
bridge or router.
Q67. What is Brouter?
Ans. Hybrid devices that combine the features of both bridges and routers.
Q68. How Gateway is
different from Routers?
Ans. A gateway operates at the upper levels of the OSI model and translates
information between two completely different network architectures or data
formats.
Q69. What are the
different type of networking / internetworking devices?
Ans. Repeater:
Also called a regenerator, it is an electronic device that operates only at
physical layer. It receives the signal in the network before it becomes weak,
regenerates the original bit pattern and puts the refreshed copy back in to the
link.
Bridges:
These operate both in the physical and data link layers of LANs of same type.
They divide a larger network in to smaller segments. They contain logic that
allow them to keep the traffic for each segment separate and thus are repeaters
that relay a frame only the side of the segment containing the intended
recipent and control congestion.
Routers:
They relay packets among multiple interconnected networks (i.e. LANs of
different type). They operate in the physical, data link and network layers.
They contain software that enable them to determine which of the several
possible paths is the best for a particular transmission.
Gateways:
They relay packets among networks that have different protocols (e.g. between a
LAN and a WAN). They accept a packet formatted for one protocol and convert it
to a packet formatted for another protocol before forwarding it. They operate
in all seven layers of the OSI model.
Q70. What is mesh
network?
Ans. A network in which there are multiple network links between computers to
provide multiple paths for data to travel.
Q71. What is passive
topology?
Ans. When the computers on the network simply listen and receive the signal,
they are referred to as passive because they don’t amplify the signal in any
way. Example for passive topology – linear bus.
Q72. What are the
important topologies for networks?
Ans. BUS topology:
In this each computer is directly connected to primary network cable in a
single line.
Advantages:
Inexpensive, easy to install, simple to understand, easy to extend.
STAR topology:
In this all computers are connected using a central hub.
Adva
ntages:
Can be inexpensive, easy to install and reconfigure and easy to trouble shoot
physical problems.
RING topology:
In this all computers are connected in loop.
Advantages:
All computers have equal access to network media, installation can be simple,
and signal does not degrade as much as in other topologies because each
computer regenerates it.
Q73. What are major
types of networks and explain
Server-based network
Peer-to-peer network.
Ans. Peer-to-peer network, computers can act as both servers sharing resources
and as clients using the resources.
Server-based networks provide centralized control of network resources and rely
on server computers to provide security and network administration
Q74. What is Protocol
Data Unit?
Ans. The data unit in the LLC level is called the protocol data unit (PDU). The
PDU contains of four fields a destination service access point (DSAP), a source
service access point (SSAP), a control field and an information field. DSAP,
SSAP are addresses used by the LLC to identify the protocol stacks on the
receiving and sending machines that are generating and using the data. The
control field specifies whether the PDU frame is a information frame (I -frame)
or a supervisory frame (S – frame) or a unnumbered frame (U – frame).
Q75. What is
difference between baseband and broadband transmission?
Ans. In a baseband transmission, the entire bandwidth of the cable is consumed
by a single signal. In broadband transmission, signals are sent on multiple
frequencies, allowing multiple signals to be sent simultaneously.
Q76. What are the
possible ways of data exchange?
Ans. (i) Simplex (ii) Half-duplex (iii) Full-duplex.
Q77. What are the
types of Transmission media?
Ans. Signals are usually transmitted over some transmission media that are
broadly classified in to two categories.
Guided Media:
These are those that provide a conduit from one device to another that include
twisted-pair, coaxial cable and fiber-optic cable. A signal traveling along any
of these media is directed and is contained by the physical limits of the
medium. Twisted-pair and coaxial cable use metallic that accept and transport
signals in the form of electrical current. Optical fiber is a glass or plastic
cable that accepts and transports signals in the form of light.
Unguided Media:
This is the wireless media that transport electromagnetic waves without using a
physical conductor. Signals are broadcast either through air. This is done
through radio communication, satellite communication and cellular telephony.
Q78. Difference
between the communication and transmission.
Ans. Transmission is a physical movement of information and concern issues like
bit polarity, synchronization, clock etc.
Communication means the meaning full exchange of information between two
communication media.
Q79.The Internet
Control Message Protocol occurs at what layer of the seven layer model?
Ans. Network
Q80.Which protocol
resolves an IP address to a MAC address?
Ans. ARP
Q81.MIDI and MPEG are
examples of what layer of the OSI seven layer model?
Ans. Presentation
Q82.What is the
protocol number for UDP?
Ans. 17
Q83.Which protocol is
used for booting diskless workstations?
Ans. RARP
Q84.Which layer is
responsible for putting 1s and 0s into a logical group?
Ans. Physical
Q85.What does ‘P’ mean
when running a Trace?
Ans. Protocol unreachable
Q86.UDP works at which
layer of the DOD model?
Ans. Host to Host
Q87.What is the
default encapsulation of Netware 3.12?
Ans. 802.2
Q88.Ping uses which
Internet layer protocol?
Ans. ICMP
Q89.Which switching
technology can reduce the size of a broadcast domain?
Ans. VLAN
Q90.What is the first
step in data encapsulation?
Ans. User information is converted into data.
Q91.What is the
protocol number for TCP?
Ans. 6
Q92.What do you use
the Aux port for?
Ans. Modem
Q93.Repeaters work at
which layer of the OSI model?
Ans. Physical
Q94.WAN stands for
which of the following?
Ans. Wide Area Network
Q95.What ISDN protocol
specifies concepts, terminology, and services?
Ans. I
Q96.LAN stands for
which of the following?
Ans. Local Are Network
Q97.DHCP stands for
Ans. Dynamic Host Configuration Protocol
Q98.What does the
acronym ARP stand for?
Ans. Address Resolution Protocol
Q99.Which layer is
responsible for identifying and establishing the availability of the intended
communication partner?
Ans. Application.
Q100.Which OSI layer
provides mechanical, electrical, procedural for activating, maintaining
physical link?
Ans. Physical.
REF: http://www.careercert.info/2009/06/100-networking-interview-questions.html
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