Category: Computer Networks Objective Questions

Computer Networks Multiple Choice Questions on “RIP v1”.

1. Which protocol should you select if the network diameter is more than 17 hops?
a) RIPv1
b) RIPv2
c) EIGRP
d) Both RIPv1 and RIPv2

Answer: a
Clarification: RIP v1 has network diameter is more than 17 hops. It uses classful routing and the routing updates are broadcasted over the network. It notifies routers about the update so that they update their own routing tables.

2. How often does a RIPv1 router broadcast its routing table by default?
a) Every 30 seconds
b) Every 60 seconds
c) Every 90 seconds
d) RIPv1 does not broadcast periodically

Answer: a
Clarification: RIPv1 router broadcasts its routing table every 30 seconds by default. The broadcasted routing table can be used by other routers to find the shortest path among the network devices.

3. Which command displays RIP routing updates?
a) Show IP route
b) Debug IP rip
c) Show protocols
d) Debug IP route

Answer: b
Clarification: The debug IP rip command is used to show the Internet Protocol (IP) Routing Information Protocol (RIP) updates being sent and received on the router. It verifies that the updates are being broadcasted and not multicasted.

4. Two connected routers are configured with RIP routing. What will be the result when a router receives a routing update that contains a higher-cost path to a network already in its routing table?
a) The updated information will be added to the existing routing table Debug IP rip
b) The update will be ignored and no further action will occur Debug IP route
c) The updated information will replace the existing routing table entry
d) The existing routing table entry will be deleted from the routing table and all routers will exchange routing updates to reach convergence

Answer: b
Clarification: When a routing update is received by a router, the router first checks the administrative distance (AD) and always chooses the route with the lowest AD. However, if two routes are received and they both have the same AD, then the router will choose the one route with the lowest metrics, or in RIP’s case, hop count.

5. You type debug IP rip on your router console and see that 172.16.10.0 is being advertised to you with a metric of 16. What does this mean?
a) The route is 16 hops away Debug IP rip
b) The route has a delay of 16 microseconds Debug IP route
c) The route is inaccessible
d) The route is queued at 16 messages a second

Answer: c
Clarification: You cannot have 16 hops on a RIP network by default, because the max default hops possible is 15. If you receive a route advertised with a metric of 16, this means it is inaccessible.

6. Default administrative distance of a static route is ________
a) 0
b) 90
c) 100
d) 1

Answer: d
Clarification: 1 is the default administrative distance of Static Route. It is used by routers to select the best path when there are different routes to the same destination. It’s used only two different routing protocols are being used.

7. Which protocol gives a full route table update every 30 seconds?
a) IEGRP
b) RIP
c) ICMP
d) IP

Answer: b
Clarification: RIP gives a full route table update every 30 seconds. The broadcasted routing table can be used by other routers to find the shortest path among the network devices.

8. _________ is the default administrative distance of RIP.
a) 0
b) 90
c) 120
d) 130

Answer: c
Clarification: The default administrative distance is the default count of numbers assigned to arbitrary routes to a destination. The default administrative distance of RIP is 120. It is used to find the shortest route amongst the number of paths available.

9. Which statement is true regarding classless routing protocol?
a) The use of discontinuous networks is not allowed
b) Use of variable length subnet masks is permitted
c) RIPv1 is a classless routing protocol
d) IGRP supports classes routing within the same autonomous system

Answer: b
Clarification: Use of variable length subnet masks is permitted in classless routing protocols. Also use of discontinuous networks is allowed in such routing protocols. RIPv1 is a classful routing protocol but RIPv2 is classless routing protocol.

10. Where should we use default routing?
a) On stub networks- which have only one exit path out of the network
b) Which have more than one exit path out of the network
c) Minimum five exit paths out of the network
d) Maximum five exit paths out of the network

Answer: a
Clarification: We must use default routing on stub networks. They have only one exit path out of the network, so there can be no specific path decided for such networks.

Computer Networks Multiple Choice Questions on “Physical Layer”.

1. The physical layer is concerned with ___________
a) bit-by-bit delivery
p) process to process delivery
c) application to application delivery
d) port to port delivery

Answer: a
Clarification: Physical layer deals with bit to bit delivery in networking. The data unit in the physical layer is bits. Process to process delivery or the port to port delivery is dealt in the transport layer. The various transmission mediums aid the physical layer in performing its functions.

2. Which transmission media provides the highest transmission speed in a network?
a) coaxial cable
b) twisted pair cable
c) optical fiber
d) electrical cable

Answer: c
Clarification: Fiber optics is considered to have the highest transmission speed among the all mentioned above. The fiber optics transmission runs at 1000Mb/s. It is called as 1000Base-Lx whereas IEEE standard for it is 802.3z. It is popularly used for modern day network connections due to its high transmission rate.

3. Bits can be sent over guided and unguided media as analog signal by ___________
a) digital modulation
b) amplitude modulation
c) frequency modulation
d) phase modulation

Answer: a
Clarification: In analog modulation, digital low frequency baseband signal (digital bit stream) is transmitted over a higher frequency. Whereas in digital modulation the only difference is that the base band signal is of discrete amplitude level. The bits are represented by only two frequency levels, one for high and one for low.

4. The portion of physical layer that interfaces with the media access control sublayer is called ___________
a) physical signalling sublayer
b) physical data sublayer
c) physical address sublayer
d) physical transport sublayer

Answer: a
Clarification: The portion of physical layer that interfaces with the medium access control sublayer is Physical Signaling Sublayer. The main function of this layer is character encoding, reception, decoding and performs optional isolation functions. It handles which media connection the signal should be forwarded to physically.

5. The physical layer provides __________
a) mechanical specifications of electrical connectors and cables
b) electrical specification of transmission line signal level
c) specification for IR over optical fiber
d) all of the mentioned

Answer: d
Clarification: Anything dealing with a network cable or the standards in use – including pins, connectors and the electric current used is dealt in the physical layer (Layer 1). Physical layer deals with bit to bit delivery of the data aided by the various transmission mediums.

6. In asynchronous serial communication the physical layer provides ___________
a) start and stop signalling
b) flow control
c) both start & stop signalling and flow control
d) only start signalling

Answer: c
Clarification: In asynchronous serial communication, the communication is not synchronized by clock signal. Instead of a start and stop signaling and flow control method is followed. Unlike asynchronous serial communication, in synchronous serial communication a clock signal is used for communication, so the start and stop method is not really required.

7. The physical layer is responsible for __________
a) line coding
b) channel coding
c) modulation
d) all of the mentioned

Answer: d
Clarification: The physical layer is responsible for line coding, channel coding and modulation that is needed for the transmission of the information. The physical configuration including pins, connectors and the electric current used is dealt in the physical layer based on the requirement of the network application.

8. The physical layer translates logical communication requests from the ______ into hardware specific operations.
a) data link layer
b) network layer
c) trasnport layer
d) application layer

Answer: a
Clarification: Physical layer accepts data or information from the data link layer and converts it into hardware specific operations so as to transfer the message through physical cables. Some examples of the cables used are optical fiber cables, twisted pair cables and co-axial cables.

9. A single channel is shared by multiple signals by ____________
a) analog modulation
b) digital modulation
c) multiplexing
d) phase modulation

Answer: c
Clarification: In communication and computer networks, the main goal is to share a scarce resource. This is done by multiplexing, where multiple analog or digital signals are combined into one signal over a shared medium. The multiple kinds of signals are designated by the transport layer which is the layer present on a higher level than the physical layer.

10. Wireless transmission of signals can be done via ___________
a) radio waves
b) microwaves
c) infrared
d) all of the mentioned

Answer: d
Clarification: Wireless transmission is carried out by radio waves, microwaves and IR waves. These waves range from 3 Khz to above 300 Ghz and are more suitable for wireless transmission. Radio waves can penetrate through walls and are used in radio communications, microwaves and infrared (IR) waves cannot penetrate through walls and are used for satellite communications and device communications respectively.

Computer Networks Multiple Choice Questions on “SMTP”.

1. When the mail server sends mail to other mail servers it becomes ____________
a) SMTP server
b) SMTP client
c) Peer
d) Master

Answer: b
Clarification: SMTP clients are the entities that send mails to other mail servers. The SMTP servers cannot send independent mails to other SMTP servers as an SMTP server. There are no masters or peers in SMTP as it is based on the client-server architecture.

2. If you have to send multimedia data over SMTP it has to be encoded into _______
a) Binary
b) Signal
c) ASCII
d) Hash

Answer: c
Clarification: Since only 7-bit ASCII codes are transmitted through SMTP, it is mandatory to convert binary multimedia data to 7-bit ASCII before it is sent using SMTP.

3. Expansion of SMTP is ________
b) Simple Message Transfer Protocol
c) Simple Mail Transmission Protocol
d) Simple Message Transmission Protocol

Answer: a
Clarification: SMTP or Simple Mail Transfer Protocol is an application layer protocol used to transport e-mails over the Internet. Only 7-bit ASCII codes can be sent using SMTP.

4. In SMTP, the command to write receiver’s mail address is written with the command _______
a) SEND TO
b) RCPT TO
c) MAIL TO
d) RCVR TO

Answer: b
Clarification: RCPT TO command is followed by the recipient’s mail address to specify where or to whom the mail is going to through the internet. If there is more than one receiver, the command is repeated for each address continually.

5. The underlying Transport layer protocol used by SMTP is ________
a) TCP
b) UDP
c) Either TCP or UDP
d) IMAP

Answer: a
Clarification: TCP is a reliable protocol, and Reliability is a mandatory requirement in e-mail transmission using SMTP.

6. Choose the statement which is wrong incase of SMTP?
a) It requires message to be in 7bit ASCII format
b) It is a pull protocol
c) It transfers files from one mail server to another mail server
d) SMTP is responsible for the transmission of the mail through the internet

Answer: b
Clarification: In SMTP, the sending mail server pushes the mail to receiving mail server hence it is push protocol. In a pull protocol such as HTTP, the receiver pulls the resource from the sending server.

7. Internet mail places each object in _________
a) Separate messages for each object
b) One message
c) Varies with number of objects
d) Multiple messages for each object

Answer: b
Clarification: It places all objects into one message as it wouldn’t be efficient enough if there are different messages for each object. The objects include the text and all the multimedia to be sent.

8. Typically the TCP port used by SMTP is _________
a) 25
b) 35
c) 50
d) 15

Answer: a
Clarification: The ports 15, 35 and 50 are all UDP ports and SMTP only uses TCP port 25 for reliability.

9. A session may include ________
a) Zero or more SMTP transactions
b) Exactly one SMTP transactions
c) Always more than one SMTP transactions
d) Number of SMTP transactions cant be determined

Answer: a
Clarification: An SMTP session consists of SMTP transactions only even if no transactions have been performed. But no transactions in the session might mean that the session is inactive or is just initiated.

10. Which of the following is an example of user agents for e-mail?
a) Microsoft Outlook
b) Facebook
c) Google
d) Tumblr

Answer: a
Clarification: Among the options, only Microsoft Outlook is an e-mail agent. Google is a search engine and Facebook, and Tumblr are social networking platforms. Gmail and Alpine are some other examples of e-mail agent.

11. When the sender and the receiver of an email are on different systems, we need only _________
a) One MTA
b) Two UAs
c) Two UAs and one MTA
d) Two UAs and two MTAs

Answer: d
Clarification: The sender’s User Agent (UA) submits the message to a Message Transfer Agent (MTA). Then the MTA sends the message to another MTA i.e. a mail relay. Then the receiver receives the message from the mail relay whenever it is available.

12. User agent does not support this ___________
a) Composing messages
b) Reading messages
c) Replying messages
d) Routing messages

Answer: d
Clarification: The user agent is basically a software program that allows the user to send, and receive e-mail messages. Routing of the message is done by the Message Transfer Agent.

Computer Networks Multiple Choice Questions on “Virtual Circuit”.

1. Which of the following is not a characteristic of Virtual Circuit Network?
a) There are setup and teardown phases in addition to the data transfer phase
b) Resources can be allocated during setup phase or on demand
c) All packets follow the same path established during the connection
d) Virtual circuit network is implemented in application layer

Answer: d
Clarification: Virtual circuit network is normally implemented in data link layer. It is a combination of circuit-switched network and datagram network which are implemented in the physical layer and network layer respectively.

2. The address that is unique in the scope of the network or internationally if the network is part of an international network is called as ______
a) Global address
b) Network address
c) Physical address
d) IP address

Answer: a
Clarification: Global address is a network address that is unique internationally and is used as a common address by all the users of the network. It is used to create a virtual circuit identifier.

3. The Identifier that is used for data transfer in virtual circuit network is called _______
a) Global address
b) Virtual circuit identifier
c) Network identifier
d) IP identifier

Answer: b
Clarification: A virtual circuit identifier is a type of numeric identifying address that is used to distinguish between different virtual circuits in a circuit-switched network. It is used for data transfer and has a switch scope.

4. Which of the following is not a phase of virtual circuit network?
a) Setup phase
b) Data transfer phase
c) Termination phase
d) Teardown phase

Answer: c
Clarification: There are three phases in a virtual circuit network: setup, data transfer and teardown phase. There is no termination phase in it.

5. Steps required in setup process are ___________
a) Setup request and acknowledgement
b) Setup request and setup response
c) Setup request and setup termination
d) Setup and termination steps

Answer: a
Clarification: Setup request (sent by a source) and acknowledgement (sent by the destination) are the steps in the setup process. Both the ends’ switches make table entries during the setup process.

6. During teardown phase, the source, after sending all the frames to destination, sends a _____ to notify termination.
a) teardown response
b) teardown request
c) termination request
d) termination response

Answer: b
Clarification: The source, after sending all the frames to destination sends teardown request to which, destination sends teardown response. The switches then delete the corresponding table entries.

7. Delay of the resource allocated during setup phase during data transfer is ________
a) constant
b) increases for each packet
c) same for each packet
d) different for each packet

Answer: c
Clarification: If a resource is allocated during setup phase, delay is same for each packet as there is only one-time delay during the setup phase and no delay during the data transfer phase.

8. Delay of the resource allocated on demand during data transfer is ________
a) constant
b) increases for each packet
c) same for each packet
d) different for each packet

Answer: d
Clarification: If a resource is to be allocated on demand during the data transfer phase, the delay for each packet would be different depending upon the resource requirement of the packets.

9. In virtual circuit network, the number of delay times for setup and teardown respectively are _______
a) 1 and 1
b) 1 and 2
c) 2 and 1
d) 2 and 2

Answer: a
Clarification: There is one-time delay for both setup and teardown phase. The one-time delay in setup phase is for resource allocation and the one-time delay in teardown phase is for the de-allocation of the resources.

10. In data transfer phase, how many columns does the table contain?
a) 1
b) 2
c) 3
d) 4

Answer: d
Clarification: The switch maintains a table for each Virtual Circuit Network. In the data transfer phase, it maintains 2 columns each for incoming data and outgoing data. The columns are in the following order: Source port, Source VCI, Destination port, Destination VCI.

Computer Networks Multiple Choice Questions & Answers on “RIP v2”.

1. Which statement is true regarding classless routing protocols?
a) The use of discontinuous networks is not allowed
b) The use of variable length subnet masks is permitted
c) RIPv1 is a classless routing protocol
d) RIPv2 supports classless routing

Answer: b
Clarification: Classful routing means that all hosts in the internetwork use the same mask. Classless routing means that you can use Variable Length Subnet Masks (VLSMs) and can also support discontinuous networking.

2. What is route poisoning?
a) It sends back the protocol received from a router as a poison pill, which stops the regular updates. The use of variable length subnet masks is permitted
b) It is information received from a router that can’t be sent back to the originating router.RIPv2 supports classless routing
c) It prevents regular update messages from reinstating a route that has just come up
d) It describes when a router sets the metric for a downed link to infinity

Answer: d
Clarification: When a network goes down, the distance-vector routing protocol initiates route poisoning by advertising the network with a metric of 16, or unreachable.

3. Which of the following is true regarding RIPv2?
a) It has a lower administrative distance than RIPv1
b) It converges faster than RIPv1
c) It has the same timers as RIPv1
d) It is harder to configure than RIPv1

Answer: c
Clarification: RIPv2 is pretty much just like RIPv1. It has the same administrative distance and timers and is configured just like RIPv1.

4. Which of the situations might not require multiple routing protocols in a network?
a) When a new Layer 2-only switch is added to the network
b) When you are migrating from one routing protocol to another
c) When you are using routers from multiple vendors
d) When there are host-based routers from multiple vendors

Answer: a
Clarification: Multiple routing protocols are required only when we need to migrate from one routing protocol to another, or when we are using routers from multiple vendors, or when there are host-based routers from multiple vendors. Routing is not a layer-2 function so we don’t require multiple routing protocols when new layer-2 switch is added.

5. Which two routing protocols can be redistributed into OSPF by a Cisco router?
a) IP EIGRP and AppleTalk EIGRP
b) AppleTalk EIGRP and RIPv2
c) RIPv2 and IP EIGRP
d) IPX RIP & AppleTalk EIGRP

Answer: c
Clarification: OSPF stands for Open Shortest Path First. It is a Link state routing protocol. IP EIGRP and RIPv2 can be redistributed into OSPF by a Cisco router.

6. Which is a reason for avoiding doing route redistribution on two routers between the same two routing domains?
a) Higher cost of two routers
b) Routing feedback
c) Cisco IOS incompatibility
d) Not possible to use two routers

Answer: b
Clarification: Routing feedback is an anomaly in which the routing protocols go back and forth between one route and another. Routing feedback is a reason for avoiding doing route redistribution on two routers between the same two routing domains.

7. What does administrative distance rank?
a) Metrics
b) Sources of routing information
c) Router reliability
d) Best paths

Answer: b
Clarification: Sources of routing information is the administrative distance rank. It is used by routers to select the best path when there are different routes to the same destination. It’s used only two different routing protocols are being used.

8. Which protocol maintains neighbor adjacencies?
a) RIPv2 and EIGRP
b) IGRP and EIGRP
c) RIPv2
d) EIGRP

Answer: c
Clarification: Neighbor adjacency refers to the formal handshake performed by neighboring routers. It is to be done before the router share any routing information. RIP V2 maintains neighbor adjacencies.

9. Which routing protocol implements the diffusing update algorithm?
a) IS-IS
b) IGRP
c) EIGRP
d) OSPF

Answer: c
Clarification: The diffusing update algorithm (DUAL) is used to maintain backup routes to a destination for when the primary route fails. EIGRP routing protocol implements the diffusing update algorithm.

10. Which protocol should you select if the network diameter is more than 17 hops?
a) RIPv1
b) RIPv2
c) EIGRP
d) OSPF

Answer: b
Clarification: RIPv2protocol should you select if the network diameter is more than 17 hops. It uses classless routing and the routing updates are broadcasted over the network. It notifies routers about the update so that they update their own routing tables.

Computer Networks Multiple Choice Questions on “Data Link Layer”.

1. The data link layer takes the packets from _________ and encapsulates them into frames for transmission.
a) network layer
b) physical layer
c) transport layer
d) application layer

Answer: a
Clarification: In computer networks, the data from application layer is sent to 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. Error control and flow control data is inserted in the frames at the data link layer.

2. Which of the following tasks is not done by data link layer?
a) framing
b) error control
c) flow control
d) channel coding

Answer: d
Clarification: Channel coding is the function of physical layer. Data link layer mainly deals with framing, error control and flow control. Data link layer is the layer where the packets are encapsulated into frames.

3. Which sublayer of the data link layer performs data link functions that depend upon the type of medium?
a) logical link control sublayer
b) media access control sublayer
c) network interface control sublayer
d) error control sublayer

Answer: b
Clarification: Media access control (MAC) deals with transmission of data packets to and from the network-interface card, and also to and from another remotely shared channel. The MAC sublayer also prevents collision using protocols like CSMA/CD.

4. Header of a frame generally contains ______________
a) synchronization bytes
b) addresses
c) frame identifier
d) all of the mentioned

Answer: d
Clarification: In a frame, the header is a part of the data that contains all the required information about the transmission of the file. It contains information like synchronization bytes, addresses, frame identifier etc. It also contains error control information for reducing the errors in the transmitted frames.

5. Automatic repeat request error management mechanism is provided by ________
a) logical link control sublayer
b) media access control sublayer
c) network interface control sublayer
d) application access control sublayer

Answer: a
Clarification: The logical link control is a sublayer of data link layer whose main function is to manage traffic, flow and error control. The automatic repeat request error management mechanism is provided by the LLC when an error is found in the received frame at the receiver’s end to inform the sender to re-send the frame.

6. When 2 or more bits in a data unit has been changed during the transmission, the error is called ____________
a) random error
b) burst error
c) inverted error
d) double error

Answer: b
Clarification: When a single bit error occurs in a data, it is called single bit error. When more than a single bit of data is corrupted or has error, it is called burst error. If a single bit error occurs, the bit can be simply repaired by inverting it, but in case of a burst error, the sender has to send the frame again.

7. CRC stands for __________
a) cyclic redundancy check
b) code repeat check
c) code redundancy check
d) cyclic repeat check

Answer: a
Clarification: Cyclic redundancy check is a code that is added to a data which helps us to identify any error that occurred during the transmission of the data. CRC is only able to detect errors, not correct them. CRC is inserted in the frame trailer.

8. Which of the following is a data link protocol?
a) ethernet
b) point to point protocol
c) hdlc
d) all of the mentioned

Answer: d
Clarification: There are many data link layer protocols. Some of them are SDLC (synchronous data link protocol), HDLC (High level data link control), SLIP (serial line interface protocol), PPP (Point to point protocol) etc. These protocols are used to provide the logical link control function of the Data Link Layer.

9. Which of the following is the multiple access protocol for channel access control?
a) CSMA/CD
b) CSMA/CA
c) Both CSMA/CD & CSMA/CA
d) HDLC

Answer: c
Clarification: In CSMA/CD, it deals with detection of collision after collision has occurred, whereas CSMA/CA deals with preventing collision. CSMA/CD is abbreviation for Carrier Sensing Multiple Access/Collision detection. CSMA/CA is abbreviation for Carrier Sensing Multiple Access/Collision Avoidance. These protocols are used for efficient multiple channel access.

10. The technique of temporarily delaying outgoing acknowledgements so that they can be hooked onto the next outgoing data frame is called ____________
a) piggybacking
b) cyclic redundancy check
c) fletcher’s checksum
d) parity check

Answer: a
Clarification: Piggybacking is a technique in which the acknowledgment is temporarily delayed so as to be hooked with the next outgoing data frame. It saves a lot of channel bandwidth as in non-piggybacking system, some bandwidth is reserved for acknowledgement.