Network Layer

1. The network layer is concerned with __________ of data.
a) bits
b) frames
c) packets
d) bytes
Answer: c
Explanation: In computer networks, the data from the application layer is sent to the transport layer and is converted to segments. These segments are then transferred to the network layer and these are called packets. These packets are then sent to data link layer where they are encapsulated into frames. These frames are then transferred to physical layer where the frames are converted to bits.

 

2. Which one of the following is not a function of network layer?
a) routing
b) inter-networking
c) congestion control
d) error control
Answer: d
Explanation: In the OSI model, network layer is the third layer and it provides data routing paths for network communications. Error control is a function of the data link layer and the transport layer.

 

3. A 4 byte IP address consists of __________
a) only network address
b) only host address
c) network address & host address
d) network address & MAC address
Answer: c
Explanation: An ip address which is 32 bits long, that means it is of 4 bytes and is composed of a network and host portion and it depends on address class. The size of the host address and network address depends upon the class of the address in classful IP addressing.

 

4. In virtual circuit network each packet contains ___________
a) full source and destination address
b) a short VC number
c) only source address
d) only destination address
Answer: b
Explanation: A short VC number also called as VCID (virtual circuit identifier) is a type of identifier which is used to distinguish between several virtual circuits in a connection-oriented circuit-switched network. Each virtual circuit is used to transfer data over a larger packet-switched network.

 

5. Which of the following routing algorithms can be used for network layer design?
a) shortest path algorithm
b) distance vector routing
c) link state routing
d) all of the mentioned
Answer: d
Explanation: The routing algorithm is what decides where a packet should go next. There are several routing techniques like shortest path algorithm, static and dynamic routing, decentralized routing, distance vector routing, link state routing, Hierarchical routing etc. The routing algorithms go hand in hand with the operations of all the routers in the networks. The routers are the main participants in these algorithms.

 

6. Which of the following is not correct in relation to multi-destination routing?
a) is same as broadcast routing
b) contains the list of all destinations
c) data is not sent by packets
d) there are multiple receivers
Answer: c
Explanation: In multi-destination routing, there is more than one receiver and the route for each destination which is contained in a list of destinations is to be found by the routing algorithm. Multi-destination routing is also used in broadcasting.

 

7. A subset of a network that includes all the routers but contains no loops is called ________
a) spanning tree
b) spider structure
c) spider tree
d) special tree
Answer: a
Explanation: Spanning tree protocol (STP) is a network protocol that creates a loop free logical topology for Ethernet networks. It is a layer 2 protocol that runs on bridges and switches. The main purpose of STP is to ensure that you do not create loops when you have redundant paths in your network.

 

8. Which one of the following algorithm is not used for congestion control?
a) traffic aware routing
b) admission control
c) load shedding
d) routing information protocol
Answer: d
Explanation: The Routing Information Protocol (RIP) is used by the network layer for the function of dynamic routing. Congestion control focuses on the flow of the traffic in the network and uses algorithms like traffic aware routing, admission control and load shedding to deal with congestion.

 

9. The network layer protocol for internet is __________
a) Ethernet
b) internet protocol
c) hypertext transfer protocol
d) file transfer protocol
Answer: b
Explanation: There are several protocols used in Network layer. Some of them are IP, ICMP, CLNP, ARP, IPX, HRSP etc. Hypertext transfer protocol is for application layer and ethernet protocol is for data link layer.

 

10. ICMP is primarily used for __________
a) error and diagnostic functions
b) addressing
c) forwarding
d) routing
Answer: a
Explanation: ICMP abbreviation for Internet Control Message Protocol is used by networking devices to send error messages and operational information indicating a host or router cannot be reached. ICMP operates over the IP packet to provide error reporting functionality as IP by itself cannot report errors.

 

11. Open Shortest Path First (OSPF) is also called as _____________
a) Link state protocol
b) Error-correction protocol
c) Routing information protocol
d) Border gateway protocol
Answer: a
Explanation: In OSPF, the link state of each path is checked, and then the shortest path is chosen among only the open state links. Each OSPF router monitors the cost of the link to each of its neighbors and then floods the link state information to other routers in the network.

 

12. The computation of the shortest path in OSPF is usually done by ____________
a) Bellman-ford algorithm
b) Routing information protocol
c) Dijkstra’s algorithm
d) Distance vector routing
Answer: c
Explanation: Shortest path in OSPF is usually computed by Dijkstra’s algorithm. It was proposed by Edsger W. Dijkstra in the year 1956. It is a greedy method algorithm and hence may not guarantee the shortest path every time, but is really fast.

 

13. Which of the following is false with respect to the features of OSPF?
a) Support for fixed-length subnetting by including the subnet mask in the routing message
b) More flexible link cost than can range from 1 to 65535
c) Use of designated router
d) Distribution of traffic over multiple paths that have equal cost to the destination
Answer: a
Explanation: OSPF provides support for variable-length sunbathing by including the subnet mask in the routing message. For fixed length subnets, there is no requirement for including the subnet mask in the routing message as there is just one subnet mask for all the subnets.

 

14. In OSPF, which protocol is used to discover neighbour routers automatically?
a) Link state protocol
b) Error-correction protocol
c) Routing information protocol
d) Hello protocol
Answer: d
Explanation: Hello protocol is used to discover neighboring routers automatically. It makes sure that the communication between neighbors is bidirectional. It’s similar to the real world moral construct of saying “Hello” to initialize the communication.

 

15. Which of the following is not a type of OSPF packet?
a) Hello
b) Link-state request
c) Link-state response
d) Link-state ACK
Answer: c
Explanation: The five types of OSPF packets are: Hello, Database description, Link-state request, Link-state update, and Link-state ACK. There is no Link-state response packet; the neighbor router sends a Link-state update packet as a response to the Link-state request packet if there is an update in the routing table.

 

16. What is the correct order of the operations of OSPF?
i – Hello packets
ii – Propagation of link-state information and building of routing tables
iii – Establishing adjacencies and synchronization of database
a) i-ii-iii
b) i-iii-ii
c) iii-ii-i
d) ii-i-iii
Answer: b
Explanation: OSPF first implements a hello protocol. Then it later on tries to establish synchronisation with database. Later on building of routing tables is done.

 

17. In OSPF header, which field is used to detect errors in the packet?
a) Type
b) Area ID
c) Authentication type
d) Checksum
Answer: d
Explanation: Checksum field is used to detect errors. It makes sure that the data portions that are being sent are all in integrity. It can detect duplicated bits. Once an error is detected, the sender has to re-transmit the data as it won’t receive an acknowledgement.

 

18. In OSPF database descriptor packet, if there are more database descriptor packets in the flow, ‘M’ field is set to ____________
a) 1
b) 0
c) more
d) -1
Answer: a
Explanation: The “M” bit is the more bit, which indicates that there are more packets to be received in the descriptor packet flow whenever it is set to 1. There is also an “I” bit which indicates if the packet is first in the flow.

 

19. In OSPF database descriptor packet, which field is used to indicate that the router is master?
a) M
b) MS
c) I
d) Options
Answer: b
Explanation: The MS bit is used to indicate if the origin of the packet is a master or a slave. If it is set to 1, the source of the packet is a master, and if it is set to 0, the source of the packet is a slave.

 

20. In OSPF database descriptor packet, which field is used to detect a missing packet?
a) LSA header
b) MS
c) Database descriptor sequence number
d) Options
Answer: c
Explanation: Sequence number field is used to detect a missing packet. The packets are to be received in order of the sequence number, so if the receiver detects that there is a sequence number skipped or missing in the order, it stops processing the further received packets and informs the sender to retransmit the packets in sequence.

 

21. An OSPF router receives an LSA, the router checks its sequence number, and this number matches the sequence number of the LSA that the receiving router already has. What does the receiving router do with the LSA?
a) Ignores the LSA
b) Adds it to the database
c) Sends newer LSU update to source router
d) Floods the LSA to the other routers
Answer: a
Explanation: When the OSPF router receives an LSA, the router checks its sequence number. If this number matches the sequence number of the LSA that the receiving router already has, the router ignores the LSA.

 

22. An OSPF router receives an LSA. The router checks its sequence number and finds that this number is higher than the sequence number it already has. Which two tasks does the router perform with the LSA?
a) Ignores the LSA
b) Adds it to the database
c) Sends newer LSU update to source router
d) Floods the LSA to the other routers
Answer: b
Explanation: An OSPF router receives an LSA. If the router checks its sequence number and finds that the number is higher than the sequence number of the LSA that it already has, the router adds it to the database, and then floods the LSA to the other routers.

 

23. An OSPF router receives an LSA. The router checks its sequence number and finds that this number is lower than the sequence number it already has. What does the router do with the LSA?
a) ignores the LSA
b) adds it to the database
c) sends newer LSU update to source router
d) floods the LSA to the other routers
Answer: c
Explanation: An OSPF router receives an LSA. If the router checks its sequence number and finds that this number is lower than the sequence number that it already has, the router sends newer LSU update to source router. The router then adds it to the database and floods it to the other routers.

 

24. Each LSA has its own age timer. By default, how long does an LSA wait before requiring an update?
a) 30 seconds
b) 1 minute
c) 30 minutes
d) 1 hour
Answer: c
Explanation: Each LSA has its own age timer. By default, an LSA waits for 30 minutes before requiring an update. The router then has to send a LSR (Link State Request) to its neighbors to get an update.

 

25. Distance vector protocols use the concept of split horizon, but link-state routing protocols, such as OSPF, do not.
a) True
b) False
Answer: b
Explanation: In Distance vector routing protocols, there is a problem called count-to-infinity which occurs regularly. So, to make sure that it does not occur, the split horizon algorithm is used. There is no requirement for it in OSPF.

 

26. The outcome of Dijkstra’s calculation is used to populate the __________
a) Topology table
b) Routing table
c) Neighbor table
d) Adjacency table
Answer: b
Explanation: The outcome of Djikstra’s calculation is the main source of entries in the routing table as it is the algorithm that is used to find the shortest path in OSPF. The calculations are done after receiving every new LSU.

 

27. What is the IP protocol number for OSPF packets?
a) 89
b) 86
c) 20
d) 76
Answer: a
Explanation: 89 is the IP protocol number for OSPF packets. 86 is the protocol number for DGP, 76 is the protocol number for Backroom-SATNET-Monitoring and 20 is the protocol number for Host Monitoring Protocol.

 

28. Which packet is NOT an OSPF packet type?
a) LSU
b) LSR
c) DBD
d) Query
Answer: d
Explanation: LSU is the Link State Update packet, LSR is the Link State Request packet and DBD is the Database Descriptor packet in OSPF. Query packet is NOT an OSPF packet type.

 

29. Which multicast address does the OSPF Hello protocol use?
a) 224.0.0.5
b) 224.0.0.6
c) 224.0.0.7
d) 224.0.0.8
Answer: a
Explanation: Hello protocol is used to discover neighboring routers automatically. It makes sure that the communication between neighbors is bidirectional. The multicast address that the OSPF Hello protocol uses is 224.0.0.5.

 

30. The Hello protocol sends periodic updates to ensure that a neighbor relationship is maintained between adjacent routers.
a) True
b) False
Answer: a
Explanation: The Hello protocol sends periodic updates to ensure that a neighbor relationship is maintained between adjacent routers. It’s similar to the real world moral construct of saying “Hello” to initialize the communication.

 

31. Datagram switching is done at which layer of OSI model?
a) Network layer
b) Physical layer
c) Application layer
d) Transport layer
Answer: a
Explanation: Datagram switching is normally done at network layer. In datagram switching, the datagram stream need not be in order as each datagram can take different routes to the destination.

 

32. Packets in datagram switching are referred to as ________
a) Switches
b) Segments
c) Datagrams
d) Data-packets
Answer: c
Explanation: As the name suggests, in datagram switching packets are called as datagram. Each datagram/packet is treated as an individual entity and routed independently through the network.

 

33. Datagram networks mainly refers to _________
a) Connection oriented networks
b) Connection less networks
c) Telephone networks
d) Internetwork
Answer: b
Explanation: The switch does not keep the information about the connection state, hence it is connection less. There is no need for establishing a handshake to begin the transmission in such networks.

 

34. Datagrams are routed to their destinations with the help of ________
a) Switch table
b) Segments table
c) Datagram table
d) Routing table
Answer: c
Explanation: Routing table is used to route the packets to their destinations. The packet/datagram header contains the destination header for the whole journey to source to the destination through the routers.

 

35. The main contents of the routing table in datagram networks are ___________
a) Source and Destination address
b) Destination address and Output port
c) Source address and Output port
d) Input port and Output port
Answer: b
Explanation: Routing table contains destination address and output port to route the packets to their destinations. The port address specifies the particular application that the packet has to be forwarded to after it has reached the destination.

 

36. Which of the following remains same in the header of the packet in a datagram network during the entire journey of the packet?
a) Destination address
b) Source address
c) Checksum
d) Padding
Answer: a
Explanation: Destination address remains same in the header during the entire journey of the packet. There is no pre-decided route for the packets so each datagram/packet is treated as an individual entity and routed independently through the network.

 

37. Which of the following is true with respect to the delay in datagram networks?
a) Delay is greater than in a virtual circuit network
b) Each packet may experience a wait at a switch
c) Delay is not uniform for the packets of a message
d) All of the mentioned
Answer: d
Explanation: The delay of each packet in a datagram network is different as each packet might take a different route to the destination. The delay includes the propagation delay and the processing delay that is induced at each stop/switch that the packet encounters in its journey.

 

38. During datagram switching, the packets are placed in __________ to wait until the given transmission line becomes available.
a) Stack
b) Queue
c) Hash
d) Routing table
Answer: b
Explanation: When there are too many packets to be transmitted and the transmission line gets blocked while transmitting some packets, the remaining packets are stored in queue during delay and are served as first in first out. The delay is called as queuing delay.

 

39. The probability of the error in a transmitted block _________ with the length of the block
a) Remains same
b) Decreases
c) Increases
d) Is not proportional
Answer: c
Explanation: Probability of the error in a transmitted block increases with the length of the block. Hence, the blocks should be as short as possible for ideal transmission with low possibility of an error.

 

40. Which of the following is false with respect to the datagram networks?
a) Number of flows of packets are not limited
b) Packets may not be in order at the destination
c) Path is not reserved
d) Delay is the same for all packets in a flow
Answer: d
Explanation: The delay of each packet in a datagram network is different as each packet might take a different route to the destination. This happens because there is no pre-decided route for the packets.

 

41. Network layer firewall works as a __________
a) Frame filter
b) Packet filter
c) Content filter
d) Virus filter
Answer: b
Explanation: As you know, firewalls are available as hardware appliances, as software-only, or a combination of the two. In every case, the purpose of a firewall is to isolate your trusted internal network (or your personal PC) from the dangers of unknown resources on the Internet and other network connections that may be harmful. The firewall prevents unauthorized access to your internal, trusted network from outside threats.

 

42. Network layer firewall has two sub-categories as _________
a) State full firewall and stateless firewall
b) Bit oriented firewall and byte oriented firewall
c) Frame firewall and packet firewall
d) Network layer firewall and session layer firewall
Answer: a
Explanation: Most network layer firewalls can operate as stateful or stateless firewalls, creating two subcategories of the standard network layer firewall. Stateful firewalls have the advantage of being able to track packets over a period of time for greater analysis and accuracy — but they require more memory and operate more slowly. Stateless firewalls do not analyze past traffic and can be useful for systems where speed is more important than security, or for systems that have very specific and limited needs. For example, a computer that only needs to connect to a particular backup server does not need the extra security of a stateful firewall.

 

43. A firewall is installed at the point where the secure internal network and untrusted external network meet which is also known as __________
a) Chock point
b) Meeting point
c) Firewall point
d) Secure point
Answer: a
Explanation: A firewall can be a PC, a router, a midrange, a mainframe, a UNIX workstation, or a combination of these that determines which information or services can be accessed from the outside and who is permitted to use the information and services from outside. Generally, a firewall is installed at the point where the secure internal network and untrusted external network meet, which is also known as a chokepoint.

 

44. Which of the following is / are the types of firewall?
a) Packet Filtering Firewall
b) Dual Homed Gateway Firewall
c) Screen Host Firewall
d) Dual Host Firewall
Answer: a
Explanation: A firewall can be a PC, a midrange, a mainframe, a UNIX workstation, a router, or combination of these. Depending on the requirements, a firewall can consist of one or more of the following functional components: Packet-filtering router

 

45. A proxy firewall filters at _________
a) Physical layer
b) Data link layer
c) Network layer
d) Application layer
Answer: d
Explanation: The application firewall is typically built to control all network traffic on any layer up to the application layer. It is able to control applications or services specifically, unlike a stateful network firewall, which is – without additional software – unable to control network traffic regarding a specific application. There are two primary categories of application firewalls, network-based application firewalls and host-based application firewalls.

 

46. A packet filter firewall filters at __________
a) Physical layer
b) Data link layer
c) Network layer or Transport layer
d) Application layer
Answer: c
Explanation: In computing, a firewall is a network security system that monitors and controls the incoming and outgoing network traffic based on predetermined security rules.[1] A firewall typically establishes a barrier between a trusted, secure internal network and another outside network, such as the Internet, that is assumed not to be secure or trusted.[2] Firewalls are often categorized as either network firewalls or host-based firewalls.

 

47. What is one advantage of setting up a DMZ with two firewalls?
a) You can control where traffic goes in three networks
b) You can do stateful packet filtering
c) You can do load balancing
d) Improved network performance
Answer: c
Explanation: DMZ stands for De-Militarized Zone. In a topology with a single firewall serving both internal and external users (LAN and WAN), it acts as a shared resource for these two zones. So load balancing can be done by adding another firewall.

 

48. What tells a firewall how to reassemble a data stream that has been divided into packets?
a) The source routing feature
b) The number in the header’s identification field
c) The destination IP address
d) The header checksum field in the packet header
Answer: a
Explanation: The source routing feature provides a path address for the packet to help the firewall to reassemble the data stream that was divided into packets. After reassembling, the firewall can then filter the stream.

 

49. A stateful firewall maintains a ___________ which is a list of active connections.
a) Routing table
b) Bridging table
c) State table
d) Connection table
Answer: a
Explanation: The routing table basically gives the state of each connection i.e. whether the connection is active or not. A routing table ensures the best performance for the stateful firewall.

 

50. A firewall needs to be __________ so that it can grow proportionally with the network that it protects.
a) Robust
b) Expansive
c) Fast
d) Scalable
Answer: b
Explanation: The firewall has to be expansive because a network is expected to grow with time and if the firewall is unable to grow with it, the firewall won’t be able to handle the growing network traffic flow and will hence fail.

 

51. Complex networks today are made up of hundreds and sometimes thousands of _________
a) Documents
b) Components
c) Servers
d) Entities
Answer: b
Explanation: Complex networks today are made up of hundreds and sometimes thousands of components. For effective functioning of these thousands of components, good network management is essential.

 

52. Performance management is closely related to _________
a) Proactive Fault Management
b) Fault management
c) Reactive Fault Management
d) Preventive Fault Management
Answer: b
Explanation: Fault management is really closely related to performance management. It is important to ensure that the network handles faults as effectively as it handles it’s normal functioning to achieve better performance management.

 

53. Configuration management can be divided into two subsystems: reconfiguration and __________
a) Documentation
b) Information
c) Servers
d) Entity
Answer: a
Explanation: The documentation subsystem of configuration management handles the log making and reporting functions of the configuration management. It also reports the errors in the network caused by the configuration’s failure.

 

54. In Network Management System, the term that is responsible for controlling access to network based on predefined policy is called ___________
a) Fault Management
b) Secured Management
c) Active Management
d) Security Management
Answer: d
Explanation: In Network Management System, the term that is responsible for controlling access to the network based on predefined policy is called security management. The security management ensures authentication, confidentiality and integrity in the network.

 

55. Control of users’ access to network resources through charges is the main responsibility of ______________
a) Reactive Fault Management
b) Reconfigured Fault Management
c) Accounting Management
d) Security Management
Answer: c
Explanation: Control of users’ access to network resources through charges is the main responsibility of accounting management. The accounting management creates a log of the users activity on the network too and goes hand-in-hand with the configurations management.

 

56. The physical connection between an end point and a switch or between two switches is __________
a) Transmission path
b) Virtual path
c) Virtual circuit
d) Transmission circuit
Answer: a
Explanation: The physical connection between an end point and a switch or between two switches is transmission path. The transmission path is the physical roadway that the packet needs to propagate in order to travel through the network.

 

57. Which of the following networks supports pipelining effect?
a) Circuit-switched networks
b) Message-switched networks
c) Packet-switched networks
d) Stream-switched networks
Answer: c
Explanation: Packet switched network is most preferred for pipelining process. Pipelining exponentially reduces the time taken to transmit a large number of packets in the network.

 

58. In Network Management System, maps track each piece of hardware and its connection to the _________
a) IP Server
b) Domain
c) Network
d) Data
Answer: c
Explanation: Network is the main entity connecting different components in a place. A network map is made to track each component and its connection to the network to ensure better network management.

 

59. MIB is a collection of groups of objects that can be managed by __________
a) SMTP
b) UDP
c) SNMP
d) TCP/IP
Answer: c
Explanation: MIB stands for Management Information Base. Simple network management controls the group of objects in management information base. It is usually used with SNMP (Simple Network Management Protocol).

 

60. A network management system can be divided into ___________
a) three categories
b) five broad categories
c) seven broad categories
d) ten broad categories
Answer: b
Explanation: The five broad categories of network management are
• Fault Management
• Configuration Management
• Accounting (Administration)
• Performance Management
• Security Management.

 

61. Which of the following is not applicable for IP?
a) Error reporting
b) Handle addressing conventions
c) Datagram format
d) Packet handling conventions
Answer: a
Explanation: The Internet Protocol is the networking protocol which establishes the internet by relaying datagrams across network boundaries. ICMP is a supporting protocol for IP which handles the Error Reporting functionality.

 

62. Which of the following field in IPv4 datagram is not related to fragmentation?
a) Flags
b) Offset
c) TOS
d) Identifier
Answer: c
Explanation: TOS-type of service identifies the type of packets. It is not related to fragmentation but is used to request specific treatment such as high throughput, high reliability or low latency for the IP packet depending upon the type of service it belongs to.

 

63. The TTL field has value 10. How many routers (max) can process this datagram?
a) 11
b) 5
c) 10
d) 1
Answer: c
Explanation: TTL stands for Time to Live. This field specifies the life of the IP packet based on the number of hops it makes (Number of routers it goes through). TTL field is decremented by one each time the datagram is processed by a router. When the value is 0, the packet is automatically destroyed.

 

64. If the value in protocol field is 17, the transport layer protocol used is _____________
a) TCP
b) UDP
c) ICMP
d) IGMP
Answer: b
Explanation: The protocol field enables the demultiplexing feature so that the IP protocol can be used to carry payloads of more than one protocol type. Its most used values are 17 and 6 for UDP and TCP respectively. ICMP and IGMP are network layer protocols.

 

65. The data field cannot carry which of the following?
a) TCP segment
b) UDP segment
c) ICMP messages
d) SMTP messages
Answer: c
Explanation: Data field usually has transport layer segments, but it can also carry ICMP messages. SMTP is an application layer protocol. First it must go through the transport layer to be converted into TCP segments and then it can be inserted into IP packets.

 

66. What should be the flag value to indicate the last fragment?
a) 0
b) 1
c) TTl value
d) Protocol field value
Answer: a
Explanation: The Flag field in the IP header is used to control and identify the fragments. It contains three bits: reserved, don’t fragment and more fragments. If the more fragments bit is 0, it means that the fragment is the last fragment.

 

67. Which of these is not applicable for IP protocol?
a) is connectionless
b) offer reliable service
c) offer unreliable service
d) does not offer error reporting
Answer: b
Explanation: IP does not provide reliable delivery service for the data. It’s dependent upon the transport layer protocols like TCP to offer reliability.

 

68. Which of the following demerits does Fragmentation have?
a) complicates routers
b) open to DOS attack
c) overlapping of fragments.
d) all of the mentioned
Answer: d
Explanation: Fragmentation makes the implementation of the IP protocol complex and can also be exploited by attackers to create a DOS attack such as a teardrop attack. Fragmentation won’t be required if the transport layer protocols perform wise segmentation.

 

69. Which field helps to check rearrangement of the fragments?
a) offset
b) flag
c) ttl
d) identifer
Answer: a
Explanation: The Fragment Offset field specifies where the fragment fits in the original datagram. The offset of the first fragment will always be 0. The size of the field (13 bits) is 3-bits shorter than the size of the total length field (16 bits).

 

70. Which of these is not applicable for IP protocol?
a) Connectionless
b) Offer reliable service
c) Offer unreliable service
d) Does not offer error reporting
Answer: b
Explanation: IP does not provide reliable delivery service for the data. It’s dependent upon the transport layer protocols like TCP to offer reliability.

 

 

72. Which of the following demerits does Fragmentation have?
a) Complicates routers
b) Open to DOS attack
c) Overlapping of fragments
d) All of the mentioned
Answer: d
Explanation: Fragmentation makes the implementation of the IP protocol complex and can also be exploited by attackers to create a DOS attack such as a teardrop attack. Fragmentation won’t be required if the transport layer protocols perform wise segmentation.

 

73. Which field helps to check rearrangement of the fragments?
a) Offset
b) Flag
c) TTL
d) Identifier
Answer: a
Explanation: The Fragment Offset field specifies where the fragment fits in the original datagram. The offset of the first fragment will always be 0. The size of the field (13 bits) is 3-bits shorter than the size of the total length field (16 bits).

 

74. In classless addressing, there are no classes but addresses are still granted in ______
a) IPs
b) Blocks
c) Codes
d) Sizes
Answer: b
Explanation: In classless addressing, there are no classes but addresses are still granted in blocks. The total number of addresses in a block of classless IP addresses = 2(32 – CIDR_value).

 

75. In IPv4 Addresses, classful addressing is replaced with ________
a) Classless Addressing
b) Classful Addressing
c) Classful Advertising
d) Classless Advertising
Answer: a
Explanation: Classful addressing is replaced with classless addressing as a large ratio of the available addresses in a class in calssful addressing is wasted. In classless addressing, one can reserve the number of IP addresses required by modifying the CIDR value and make sure that not many addresses are wasted.

 

76. First address in a block is used as network address that represents the ________
a) Class Network
b) Entity
c) Organization
d) Codes
Answer: c
Explanation: First address in a block is used as network address that represents the organization. The network address can be found by AND’ing any address in the block by the default mask. The last address in a block represents the broadcast address.

 

77. In classful addressing, a large part of available addresses are ________
a) Organized
b) Blocked
c) Wasted
d) Communicated
Answer: c
Explanation: In classful addressing, a large part of available addresses are wasted. Thus to solve this classful addressing is replaced with classless addressing where one can reserve the number of IP addresses required by modifying the CIDR value and make sure that not many addresses are wasted.

 

 

78. Network addresses are a very important concept of ________
a) Routing
b) Mask
c) IP Addressing
d) Classless Addressing
Answer: c
Explanation: Network addresses are a very important concept of IP addressing. The first address in a block is used as network address that represents the organization. The network address can be found by AND’ing any address in the block or class by the default mask.

 

79. Which of this is not a class of IP address?
a) Class E
b) Class C
c) Class D
d) Class F
Answer: d
Explanation: Class F is not a class of IP addressing. There are only five classes of IP addresses: Class A (0.0.0.0 to 127.255.255.255), Class B (128.0.0.0 to 191.255.255.255), Class C (192.0.0.0 to 223.255.255.255), Class D (224.0.0.0 to 239.255.255.255), and Class E (240.0.0.0 to 255.255.255.255).

 

80. The size of an IP address in IPv6 is _________
a) 4 bytes
b) 128 bits
c) 8 bytes
d) 100 bits
Answer: b
Explanation: An IPv6 address is 128 bits long. Therefore, 2128 i.e. 340 undecillion addresses are possible in IPv6. IPv4 has only 4 billion possible addresses and IPv6 would be a brilliant alternative in case IPv4 runs out of possible new addresses.

 

81. The header length of an IPv6 datagram is ___________
a) 10bytes
b) 25bytes
c) 30bytes
d) 40bytes
Answer: d
Explanation: IPv6 datagram has fixed header length of 40bytes, which results in faster processing of the datagram. There is one fixed header and optional headers which may or may not exist. The fixed header contains the mandatory essential information about the packet while the optional headers contain the optional “not that necessary” information.

 

82. In the IPv6 header, the traffic class field is similar to which field in the IPv4 header?
a) Fragmentation field
b) Fast-switching
c) ToS field
d) Option field
Answer: c
Explanation: The traffic class field is used to specify the priority of the IP packet which is a similar functionality to the Type of Service field in the IPv4 header. It’s an 8-bit field and its values are not defined in the RFC 2460.

 

83. IPv6 does not use _________ type of address.
a) broadcast
b) multicast
c) anycast
d) unicast
Answer: a
Explanation: There is no concept of broadcast address in IPv6. Instead, there is an anycast address in IPv6 which allows sending messages to a group of devices but not all devices in a network. Anycast address is not standardized in IPv4.

 

84. Which among the following features is present in IPv6 but not in IPv4?
a) Fragmentation
b) Header checksum
c) Options
d) Anycast address
Answer: d
Explanation: There is an anycast address in IPv6 which allows sending messages to a group of devices but not all devices in a network. Anycast address is not standardized in IPv4.

 

85. The _________ field determines the lifetime of IPv6 datagram
a) Hop limit
b) TTL
c) Next header
d) Type of traffic
Answer: a
Explanation: The Hop limit value is decremented by one by a router when the datagram is forwarded by the router. When the value becomes zero the datagram is discarded. The field is 8-bits wide, so an IPv6 packet can live up to 255 router hops only.

 

86. Dual-stack approach refers to _________
a) implementing Ipv4 with 2 stacks
b) implementing Ipv6 with 2 stacks
c) node has both IPv4 and IPv6 support
d) implementing a MAC address with 2 stacks
Answer: c
Explanation: Dual-stack is one of the approaches used to support IPv6 in already existing systems. ISPs are using it as a method to transfer from IPv4 to IPv6 completely eventually due to the lower number of possible available addresses in IPv4.

 

87. Suppose two IPv6 nodes want to interoperate using IPv6 datagrams, but they are connected to each other by intervening IPv4 routers. The best solution here is ________
a) Use dual-stack approach
b) Tunneling
c) No solution
d) Replace the system
Answer: b
Explanation: The IPv4 routers can form a tunnel in which at the sender’s side, the IPv6 datagram is encapsulated in to IPv4, and at the receiver’s side of the tunnel, the IPv4 packet is stripped and the IPv6 packet is sent to the receiver.

 

88. Teredo is an automatic tunneling technique. In each client the obfuscated IPv4 address is represented by bits ______
a) 96 to 127
b) 0 to 63
c) 80 to 95
d) 64 to 79
Answer: a
Explanation: Teredo is a technique through which gives the possibility for full IPv6 network connectivity to IPv6 capable hosts which are currently on an IPv4 network. Bits 96 to 127 in the datagram represents obfuscated 1Pv4 address of the IPv4 network.