Top Interview Questions for Network Engineers, Part 2

The continuation of the previous post, stolen from router-switch.com Blog


Q51. What are the data units at different layers of the TCP / IP protocol site?

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.


Advantages:

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 and 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?


Q96.LAN stands for which of the following?


Ans. Local Area 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.