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Computer Networking
Undergraduate 2

Additional Computer Networking Flashcards





Which one of the following characteristics is true regarding the use of hubs and switches?

A. Hubs can have their ports be configured with VLANs

B. Using hubs is costly with regard to bandwidth availability.

C. Switches can not forward broadcasts.

D. Switches are more efficient than hubs in processing frames.

E. Switches increase the number of collision domains in the network.


Answer: E


 Switches increases the number of collisions domains in the network. Switches that are configured with VLANs will reduce the size of the collision domains by increasing the number of collision domains in a network, but making them smaller than that of one big, flat network.



When comparing and contrasting the similarities and differences between bridges and switches, which of the following are valid statements? Choose all the valid answer choices)

A. Bridges are faster than switches because they have fewer ports.

B. A switch is a multiport bridge,

C. Bridges and switches learn MAC addresses by examining the source MAC address of each frame received.

D. A bridge will forward a broadcast but a switch will not.

E. Bridges and switches increase the size of a collision domain.

F. None of the above statements are true


Answer: B, C

Explanation: Both bridges and switches build the bridge table by listening to incoming frames and examining the source MAC address in the frame. Switches are multiport bridges that allow you to create multiple broadcast domains. Each broadcast domain is like a distinct virtual bridge within a switch



Which of the following correctly describe the various functions and virtues of a router? (Select all valid answer choices)

A. Packet switching

B. Collision prevention on a LAN segment.

C. Packet filtering

D. Broadcast domain enlargement

E. Broadcast forwarding

F. Internetwork communication

G. None of the above


Answer: A, C, F

Explanation: The main function of a router is to connect different, separated networks together. In doing so, switching packets from one network to another is a primary function, along with providing for communication between networks. As an additional feature, routers are capable of providing filtering on a network address and application port level, so choice C is also correct.



The LAN needs are expanding at the Certkiller corporate office, which is quickly growing. You are instructed to enlarge the area covered by a single LAN segment on the Certkiller network. Which of the following are layer 1 devices that you can use? (Choose all that apply.)

A. A switch

B. A router

C. A network adapter card

D. A hub

E. A repeater


Answer: D, E

Explanation: A hub simply repeats the electrical signal and makes no attempt to interpret the electrical signal (layer 1) as a LAN frame (Layer 2). So, a hub actually performs OSI layer 1 functions, repeating an electrical signal, whereas a switch performs OSI layer 2 functions, actually interpreting Ethernet header information, particularly addresses, to make forwarding decisions. Hubs can be used to increase the number of stations that can be supported on a LAN. Because the repeater does not interpret what the bits mean, but does examine and generate electrical signals, a repeater is considered to operate at Layer 1. Repeaters can be used to physically extend the LAN to greater distances.


QUESTION 5: Cisco is the leader in the router market space. What basic functions do their routers perform in a network? (Choose two)

A. The microsegmentation of broadcast domains

B. Path selection

C. Packet switching

D. Bridging between LAN segments

E. Access layer security

F. VLAN membership assignment

G. Application optimization


Answer: B, C

Explanation: The primary functions of a router are: Packet Switching and Path Selection. It is the routers job to determine the best method for delivering the data, and switching that data as quickly as possible.



The Certkiller network administrator needs to determine what LAN devices to install on the Certkiller network. What are two advantages of using Layer 2 Ethernet switches over hubs? (Choose two)

A. Allowing simultaneous frame transmissions

B. Increasing the size of broadcast domains

 C. Increasing the maximum length of UTP cabling between devices

 D. Filtering frames based on MAC addresses

E. Decreasing the number of collision domains


Answer: A, D

Explanation: A: A half duplex connection is where only one device can send or receive at a time. A full duplex connection is where both devices can send and receive at the same time. Thus, if you have a 100Mb half-duplex connection, only sending at 100Mb OR receiving at 100Mb can happen at the same time. If you have a 100Mb full duplex connection, you can effectively get 200Mb out of the link because you could be sending 100Mb and receiving 100Mb at the same time. D: Switches are capable of filtering frames based on any Layer 2 fields. For example, a switch can be programmed to reject (not forward) all frames sourced from a particular network. Because link layer information often includes a reference to an upper-layer protocol, switches usually can filter on this parameter. Furthermore, filters can be helpful in dealing with unnecessary broadcast and multicast packets

QUESTION 7:  CDP is being used throughout the Certkiller network. What are two reasons why theCertkiller network administrator would use CDP? (Choose two) A. To determine the status of network services on a remote deviceB. To obtain the IP Address of a connected device in order to telnet to the deviceC. To verify the type of cable interconnecting two devicesD. To verify Layer 2 connectivity between two devices when Layer 3 failsE. To obtain VLAN information from directly connected switchesF. To determine the status of the routing protocols between directly connected routersG. To support automatic network failover during outages 

Answer: B, D

Explanation:Cisco Discovery Protocol (CDP) is a proprietary protocol designed by Cisco to help administrators collect information about both locally attached and remote devices. By using CDP, you can gather hardware and protocol information about neighbor devices, which is useful info for troubleshooting and documenting the network. You can use: Show cdp neighbor Show cdp neighbor details Commands to gather the information of connected neighbors.



CDP is running between two Certkiller devices. What information is supplied by CDP?

(Select three)

A. Device Identifiers

B. Capabilities list

C. Platform

D. Route identifier

 E. Neighbor traffic data



Two Certkiller offices are connected as shown below:

        Two buildings on the London campus of a the Certkiller corporation must be connected to use Ethernet with a bandwidth of at least 100 Mbps. Certkiller is concerned about possible problems from voltage potential differences between the two buildings. Which media type should be used for the connection?

A. Coaxial cable

B. Fiber optic cable

C. UTP cable

D. STP cable

E. None of the above


Answer: B


Current Ethernet technology typically comes via either copper UTP or fiber cables. In this scenario the distance between the buildings is only 55 meters so either copper orfiber could be used, as the distance limitation for 100M UTP Ethernet is 100 meters. However, fiber would be a better fit as it is not prone to errors that could occur due to the voltage potential differences. Because fiber is a dielectric material, it's not susceptible to electrical interference. FO-product vendors also claim that fiber systems make secure communications easier. Interference immunity and lack of emissions are givens in FO

systems and in the fiber medium itself.



Refer to the Certkiller network shown below:


You work as a network technician at Certkiller .com. Please study the exhibit carefully. Based on the information shown above, what is needed to allow host Certkiller 1 to ping host Certkiller 2?

A. A crossover cable connecting the switches 

 B. A backbone switch connecting the switches with either fiber optic or straight-through cables

C. A straight-through cable connecting the switches

D. A CSU/DSU connected to the switches with straight-through cables

E. A router connected to the switches with straight-through cables


Answer: E


Routers are Layers 3 devices used for inter-network communication. In this scenario there are two different networks, so both switches need to connect to a router using straight-through cables. A straight-through cable is used to connect two different devices like, switch to router,host to switch. Since we need to insert a router for communication between the two switches, straight through cables will be used between the switches and the router.





Ethernet interfaces

B. A router with two Ethernet interfaces

C. A switch with one Ethernet and one serial interface

D. A router with one Ethernet A new Certkiller office is opening, and a network device needs to be installed in the place of the icon labeled Network Device to accommodate a leased line T1 to the Internet. Which network device and interface configuration meets the minimum requirements for this installation?

A. A switch with twoand one serial interface

 E. A router with one Ethernet and one modem interface F. None of the above


Answer: D



Only a router can terminate a leased line T1 access circuit, and only a router can connecttwo different IP networks. Here, we will need a router with two interfaces, one serialconnection for the T1 and one Ethernet interface to connect to the switch on the LAN. 






As a CCNA candidate, you must know the various layers of the OSI model. At which layers of the OSI Model do Wide Area Networks operate in? (Choose two)

A. Physical Layer

B. Datalink Layer

C. Network Layer

D. Session Layer

E. Transport Layer

F. Presentation Layer

G. Application Layer


Answer: A, B



A WAN is a data communications network that covers a relatively broad geographic areaand that often uses transmission facilities provided by common carriers, such astelephone companies. WAN technologies generally function at the lower two layers ofthe OSI reference model: the physical layer and the data link layer as shown below.



Occasionally WAN's would also be considered to operate at layer 3, but since thisquestion asked for only 2 choices layers 1 and 2 are better choices



While troubleshooting a connectivity problem on the network, you issue the ping command from your PC command prompt, but the output shows "request times out." At which OSI layer is this problem associated with? 

A. The data link layer

B. The application layer

C. The access layer

D. The session layer

E. The network layer


Answer: E



TCP/IP includes ICMP, a protocol designed to help manage and control the operation ofa TCP/IP network. The ICMP protocol provides a wide variety of information about anetwork's health and operational status. Control message is the most descriptive part of aname. ICMP helps control and manage IP's work and therefore is considered part ofTCP/IP's network layer.




 A host computer has been correctly configured with a static IP address, but the default gateway is incorrectly set. Which layer of the OSI model will be first affected by this configuration error?

A. Layer 1

B. Layer 2

C. Layer 3

D. Layer 4

E. Layer 5

 F. Layer 6

 E. Layer 7


Answer: C



IP Addressing and IP routing resides on the OSI Network layer, which is layer 3.





Which layer of the OSI reference model is responsible for ensuring reliable end-to-end delivery of data?

A. Application

B. Presentation

 C. Session

 D. Transport

 E. Network

F. Data-Link


Answer: D



A key function of the transport layer is to provide connection services for the protocolsand applications that run at the levels above it. These can be categorized as eitherconnection-oriented services or connectionless services. Some protocol suites, such as

TCP/IP, provide both a connection-oriented and a connectionless transport layerprotocol, to suit the needs of different applications.

The transport layer is also the place in the layer stack where functions are normallyincluded to add features to end-to-end data transport. Where network layer protocols arenormally concerned with just "best effort" communications, where delivery is notguaranteed. Transport layer protocols are given intelligence in the form of algorithms that

ensure that reliable and efficient communication between devices takes place. Thisencompasses several related jobs, including lost transmission detection and handling, andmanaging the rate at which data is sent to ensure that the receiving device is not overwhelmed.

Transmission quality, meaning ensuring that transmissions are received as sent, is soimportant that some networking references define the transport layer on the basis ofreliability and flow-control functions. However, not all transport layer protocols provide

these services. Just as a protocol suite may have a connection-oriented and aconnectionless transport layer protocol, it may also have one that provides reliability anddata management services, and one that does not. Again, this is the case with TCP/IP:there is one main transport layer protocol; TCP, that includes reliability and flow control

features, and a second, UDP, that doesn't.




At which OSI layer is a logical path created between two host systems named CK1
and CK2 on the Certkiller LAN?

A. Physical
B. Session
C. Data link
D. Transport
E. Network
F. Application
G. Presentation

Answer: E



The Network layer (also called layer 3) manages device addressing, tracks the location of

devices on the network, and determines the best way to move data, which means that the

Network layer must transport traffic between devices that aren't locally attached. Routers

(layer 3 devices) are specified at the Network layer and provide the routing services

within an internetwork.


Which OSI layer is associated with the following: The acknowledgement of
transmissions, sequencing, and flow control across a network?

A. Layer 2
B. Layer 3
C. Layer 4
D. Layer 5
E. Layer 6
F. Layer 7

Answer: C




The Transport layer (Layer 4) defines several functions, including the choice of

protocols. The most important Layer 4 functions are error recovery and flow control. The

transport layer may provide for retransmission, i.e., error recovery, and may use flow

control to prevent unnecessary congestion by attempting to send data at a rate that the

network can accommodate, or it might not, depending on the choice of protocols.

Multiplexing of incoming data for different flows to applications on the same host is also

performed. Reordering of the incoming data stream when packets arrive out of order is

included. Examples include: TCP, UDP, and SPX.


Which OSI layer header contains the address of a destination host that is on another

A. Application
B. Presentation
C. Session
D. Transport
E. Network
F. Data link
G. Physical

Answer: E



Only network address contains this information. To transmit the packets the sender uses

network address and datalink address. But the layer 2 address represents just the address

of the next hop device on the way to the sender. It is changed on each hop. Network

address remains the same

Which of the following correctly describe steps in the OSI data encapsulation
process? (Choose two)

A. The presentation layer translates bits into voltages for transmission across the physical
B. The transport layer divides a data stream into segments and adds reliability and flowcontrol information.


C. Packets are created when the network layer adds Layer 3 addresses and control
information to a segment.
D. The data link layer adds physical source and destination addresses and an FCS to the
E. Packets are created when the network layer encapsulates a frame with source and
destination host addresses and protocol-related control information.

Answer: B, C



The Transport Layer:

You can think of the transport layer of the OSI model as a boundary between the upper

and lower protocols. The transport layer provides a data transport service that shields the

upper layers from transport implementation issues such as the reliability of a connection.

The transport layer provides mechanisms for:

Segmenting upper layer application

The establishment, maintenance, and orderly termination of virtual circuits

information flow control and reliability via TCP

Transport fault detection and recovery 

The Network Layer:

Layer three of the OSI model is the network layer.

The network layer creates and sends packets from source network to destination 


it provides consistent end-to-end packet delivery service and control information

it creates and uses layer3 addresses for use in path determination and to forward 


Incorrect Answers:

A: This correctly describes the physical layer, not the presentation layer.

D: Although the data link layer adds physical (MAC) source and destination addresses, it

adds it to a frame, not a segment.

E: Packets are encapsulated, not frames.


When files are transferred between a host and an FTP server, the data is divided
into smaller pieces for transmission. As these pieces arrive at the destination host,
they must be reassembled to reconstruct the original file. What provides for the
reassembly of these pieces into the correct order?

A. The sequence number in the TCP header
B. The Start Frame Delimiter in the 802.3 Preamble
C. The TTL in the IP header
D. The acknowledgement number in the segment header
E. The frame check sequence in the Ethernet frame trailer

Answer: A




The Transport layer can provide reliable networking via acknowledgments, sequencing,

and flow control.

Acknowledgments Delivered segments are acknowledged to the sender. If they are not

acknowledged, the sender will retransmit.

* Sequencing Data segments are sequenced into their original order when they arrive at

the destination.

* Flow Control Provides buffer controls that prevent packet flooding to the destination

host. Buffers store bursts of data for processing when the transmission is complete.

Layer 4 protocols include the following:

* Transmission Control Protocol (TCP)

* User Datagram Protocol (UDP)

Sequenced Packet Exchange (SPX)A reliable communications protocol created by

Novell NetWare


Network equipment supporting the use of flow control mechanisms has been
recently installed in the Certkiller network. What is the purpose of flow control in a
data network?

A. It ensures that data is retransmitted if an acknowledgment is not received.
B. It reassembles segments in the correct order on the destination device.
C. It provides a mechanism for the receiver to control the transmission speed.
D. It regulates the size of each datagram segment.
E. All of the above are functions of flow control

Answer: C



Flow control paces the transmission of data between a sending device and a receiving

device. Flow control ensures that the receiving device can absorb the data sent to it

before the sending device sends more. When the buffers on the receiving device are full,

a message is sent to the sending device to suspend transmission until the data in the

buffers has been processed.

Incorrect Answers:


A. Data retransmission mechanisms are not handled by control. They are most often

handled by transport layer protocols such as TCP.

B. This describes the reassembly portion of the segmentation and reassembly (SAR)

function of network equipment.


You need to describe the various types of flow control to your co-workers. Which of
the following are types of flow control that can be used in a network? (Choose three)

A. Congestion avoidance
B. Windowing
C. Cut-through
D. Buffering
E. Load Balancing
F. Fast Forward

Answer: A, B, D 



Part of the Certkiller network is displayed below:


 Study the exhibit shown above. Host Certkiller A has established a connection with the Certkiller II server attached to interface E0 of the Certkiller 2 router. Which of the following statements describe the information contained in protocol data units sent from Host Certkiller to Certkiller II?

(Choose three)

A. The destination port number in a segment header will have a value of 80

B. The destination IP address of a packet will be the IP address of the E0 interface of the Certkiller 1 router

C. The destination IP address of a packet will be the IP address of the network interface of the Certkiller II server

D. The destination address of a frame will be the MAC address of the E0 interface of Certkiller 1 router


Answer: A, C, D


Which protocol below uses TCP port 443 at layer 4?

D. Telnet
F. None of the above

Answer: B



HTTPS is the secured version of the HTTP application, which normally uses 128 bit SSL

encryption to secure the information sent and received on a web page. An example is a

banking web site, or a trustworthy shopping web site that takes credit card information. It

is an application layer protocol which uses TCP port 443.

Incorrect Answers

A. HTML is not a protocol.

C. TFTP uses UDP port 69.

D. Telnet uses TCP port 23.

E. SMTP uses TCP port 25.




As a CCNA candidate, you will be expected to know the OSI model very well.
Which of the following are associated with the application layer (layer 7) of the OSI
model? (Choose two)

B. Telnet
D. Ping
Answer: B, C 


The application layer is the top layer of the OSI model and is used to describe the enduser applications that can be used over a network.Layer Name ExamplesApplication (layer 7) Telnet, HTTP, FTP, WWW browsers, NFS, SMTP gateways,SNMPIncorrect Answers: A. TCP resides at layer 4.D. ARP is a function of the data link layer, which is layer 2.E. IP is used at layer 3 (network layer). 

As the Certkiller network administrator, you are required to have a firm
understanding of the OSI model. Why does the data communication industry use
the layered OSI reference model? (Choose two)

A. It enables equipment from different vendors to use the same electronic components,
thus saving research and development funds
B. It encourages industry standardization by defining what functions occur at each layer
of the model
C. It divides the network communication process into smaller and simpler components;
thus aiding component development, design and troubleshooting
D. It provides a means by which changes in functionality in one layer require changes in
other layers
E. It supports the evolution of multiple competing standards and thus provides business
opportunities for equipment manufacturers
Answer: B, C Explanation:  The OSI (Open System Interconnection) reference model was created as a reference pointfor communications devices. A layered approach is used to segment the entiretelecommunications process into a series of smaller steps.A is correct because it encourages a level of standardization by encouraging thatfunctions be compared to known layers. D is also correct because it allows engineers tofocus on the development, refining, and perfection of simpler components.

Which of the protocols below use TCP at the transport layer? (Select four)
Answer: B, D, E, F Explanation: 

SMTP (Simple Mail Transfer Profile for email), FTP (File Transfer Protocol), andHTTP/HTTPS (Hyper Text Transfer Protocol for internet) all use TCP because of thereliable delivery mechanism. SMTP uses TCP port 25, FTP uses TCP ports 20 and 21,HTTP uses TCP port 80, and HTTPS uses TCP port 443.Incorrect Answers:A, C: SNMP and TFTP use UDP as the transport mechanism. Generally speaking,protocols that use the keywords "trivial" or "simple" uses UDP, since connectionless, best effort delivery mechanism usually suffice.Reference: CCNA Self-Study CCNA INTRO exam certification Guide (Cisco Press,ISBN 1-58720-094-5) Page 163. 
QUESTION 29:  Exhibit:


The exhibit above displays the partial contents of an encapsulation header.Which of the following are true of the network traffic represented in this diagram?

 (Select three) 

A. This is a UDP header

B. This is an OSI layer 4 header.

C. This is traffic from an FTP server.

D. This is traffic from an Telnet client.

E. The last PDU received in this session had a sequence number of 292735. 




Answer: B, C, E

 Explanation:  As the header contains the sequence number and ACK number fields, it represents a TCPheader. Choice B is correct as TCP works on Layer 4 i.e. Transport Layer.Source Port mentioned in the header is 21 which indicate it is FTP Traffic because FTP

uses port 20 and 21 for data and control. So choice C is correct.

The acknowledgment number refers to the sequence number of the last PDU received,which is 292735, making choice E also correct.




 Acknowledgements, sequencing, and flow control are functions that are handled bywhich layer of the OSI model?  A. Layer 5

B. Layer 4

C. Layer 7

D. Layer 6

E. Layer 3

F. Layer 2

G. Layer 1

Answer: B


 A receiving host has failed to receive all of the segments that it should acknowledge.What can the host do to improve the reliability of this communication session? 

A. Start a new session using UDP

B. Obtain a new IP address from the DHCP server

C. Use a different source port for the session

D. Decrease the sequence number

E. Decrease the window size 


Answer: E 

Explanation:  A TCP window the amount of outstanding (unacknowledged by the recipient) data asender can send on a particular connection before it gets an acknowledgment back from the receiver that it has gotten some of it.For example if a pair of hosts are talking over a TCP connection that has a TCP windowsize of 64 KB (kilobytes), the sender can only send 64 KB of data and then it must stopand wait for an acknowledgment from the receiver that some or all of the data has beenreceived. If the receiver acknowledges that all the data has been received then the senderis free to send another 64 KB.One way to improve the reliability of the TCP connection is to reduce the window sizethat the receiver needs to receive before sending an acknowledgement. However, this willreduce throughput as more segments and acknowledgements will need to be sent in orderto transfer the same amount of data.

You have set up an Internet based FTP server, where people can upload anddownload files. In terms of the OSI model, what is the highest layer used during theFTP sessions.
 A. Application
B. Presentation
C. Session
D. Transport
E. Internet
F. Data Link
G. Physical

Answer: A Explanation: 

 The application layer is the highest layer (layer 7) of the OSI model, and is reserved forend user applications. Since FTP is itself an application, layer 7 is the highest layer used.Incorrect Answers:B, C, D, E, F, G. In any given FTP session, all of these layers will be used at some pointbut they are incorrect because the question asked for the highest layer used by FTP.



Which Layer 4 protocol is used for a Telnet connection between two Certkiller  routers?  








Answer:  D Explanation: 

 TCP is a reliable connection-oriented protocol. TCP uses acknowledgments, sequencing,and flow control to ensure reliability. Telnet uses TCP port 23.



DRAG DROPYou work as a network administrator at Certkiller .com.Your boss, Mrs. Certkiller, is interested in the OSI layers. Match the terms with the appropriate layer. Some options are not used.





Explanation:  The Transport layer segments and reassembles data into a data stream. Services locatedin the Transport layer segment and reassemble data from upper-layer applications and

unite it into the same data stream. They provide end-to-end data transport services andcan establish a logical connection between the sending host and destination host on aninternetwork.TCP and UDP transport protocol lies on Transport Layer, which break down the datacoming from upper layer into segment.Windows are used to control the amount of outstanding, unacknowledgeddata segments that is also on Transport Layer.Network Layer:The Network layer (also called layer 3) manages device addressing, tracks the location ofdevices on the network, and determines the best way to move data, which means that theNetwork layer must transport traffic between devices that aren't locally attached. Routers(layer 3 devices) are specified at the Network layer and provide the routing serviceswithin an internetwork.Protocol Data Packets (PDU) on Network Layer is known as Packets. Routing andRouted protocols are lies on Network Layer.Routing Protocol: RIP, IGRP, EIGRP, OSPF, BGPRouted Protocol: IP, IPX  




Refer to the following exhibit


What data structure is described in the exhibit shown above?

  A. IP datagram

B. TCP segment

C. Ethernet frame

D. UDP datagram

E. FDDI frame

F. Token Ring frame

G. None of the above


Answer: B 


The Figure below illustrates the fields and overall format of a TCP packet Twelve fields comprise a TCP packet.

Twelve fields comprise a TCP packet


The following descriptions summarize the TCP packet fields illustrated above.1. SourcePort and DestinationPort-Identifies points at which upper-layer source anddestination processes receive TCP services.2.3. Sequence Number-Usually specifies the number assigned to the first byte of data in thecurrent message. In the connection-establishment phase, this field also can be used toidentify an initial sequence number to be used in an upcoming transmission.4.5. Acknowledgment Number-Contains the sequence number of the next byte of data thesender of the packet expects to receive.6.7. Data Offset-Indicates the number of 32-bit words in the TCP header.8.9. Reserved-Remains reserved for future use.10.11. Flags-Carries avariety of control information, including the SYN and ACK bits used for connectionestablishment, and the FIN bit used for connection termination.12.13. Window-Specifies the size of the sender's receive window (that is, the buffer spaceavailable for incoming data).14.15. Checksum-Indicates whether the header was damaged in transit.16.17. Urgent Pointer-Points to the first urgent data byte in the packet.18.19. Options-Specifies various TCP options.Data-Contains upper-layer information.
QUESTION 36: FTP, Telnet, DNS, and SMTP are all protocols being used in the Certkiller network.Of these, which uses both TCP and UDP ports? A. TelnetB. FTPC. DNSD. SMTPE. None of the above 

Answer: C 

Explanation:  The following port numbers for the protocols listed above are as follows:FTP: TCP Port 20 and 21SMTP: TCP Port 25Telnet: TCP Port 23DNS: both TCP and UDP Port 53

QUESTION 37:  ICMP is often used in troubleshooting and verifying network. What statements are

true regarding ICMP packets?

(Choose two) A. They acknowledge receipt of TCP segments.B. They guarantee datagram delivery.C. They can provide hosts with information about network problems.D. They are encapsulated within IP datagrams.E. They are encapsulated within UDP datagrams.F. They are encapsulated within TCP datagrams. 

 Answer: C, D 

Explanation:  ping may be used to find out whether the local machines are connected to the network orwhether a remote site is reachable. This tool is a common network tool for determiningthe network connectivity which uses ICMP protocol instead of TCP/IP and UDP/IP. Thisprotocol is usually associated with the network management tools which provide networkinformation to network administrators, such as ping and traceroute (the later also uses theUDP/IP protocol).ICMP is quite different from the TCP/IP and UDP/IP protocols. No source anddestination ports are included in its packets. Therefore, usual packet-filtering rules forTCP/IP and UDP/IP are not applicable. Fortunately, a special "signature" known as thepacket's Message type is included for denoting the purposes of the ICMP packet. Mostcommonly used message types are namely, 0, 3, 4, 5, 8, 11, and 12 which represent echoreply, destination unreachable, source quench, redirect, echo request, time exceeded, and  



Although TCP segments are similar to UDP segments, TCP packets contains some additional fields. Which of the following are found in a TCP header, but not in aUDP header?

 (Choose three) A. ChecksumB. Sequence numberC. Destination portD. Window sizeE. Acknowledgment numberF. Source port
Answer: B, D, E 

Explanation:  The Figure below illustrates the fields and overall format of a TCP packet.Twelve fields comprise a TCP packet


TCP Packet Field DescriptionsThe following descriptions summarize the TCP packet fields illustrated in Figure 30-10:1. Source Port and Destination Port-Identifies points at which upper-layer source anddestination processes receive TCP services.

2. Sequence Number-Usually specifies the number assigned to the first byte of data in thecurrent message. In the connection-establishment phase, this field also can be used todentify an initial sequence number to be used in an upcoming transmission.

3. Acknowledgment Number-Contains the sequence number of the next byte of data thesender of the packet expects to receive.4. Data Offset-Indicates the number of 32-bit words in the TCP header.5. Reserved-Remains reserved for future use.6. Flags-Carries a variety of control information, including the SYN and ACK bits usedfor connection establishment, and the FIN bit used for connection termination.7. Window-Specifies the size of the sender's receive window (that is, the buffer spaceavailable for incoming data).8. Checksum-Indicates whether the header was damaged in transit.9. Urgent Pointer-Points to the first urgent data byte in the packet.10. Options-Specifies various TCP options.11. Data-Contains upper-layer information.User Datagram Protocol (UDP)The User Datagram Protocol (UDP) is a connectionless transport-layer protocol (Layer 4)that belongs to the Internet protocol family. UDP is basically an interface between IP andupper-layer processes. UDP protocol ports distinguish multiple applications running on asingle device from one another.Unlike the TCP, UDP adds no reliability, flow-control, or error-recovery functions to IP.Because of UDP's simplicity, UDP headers contain fewer bytes and consume lessnetwork overhead than TCP.UDP is useful in situations where the reliability mechanisms of TCP are not necessary,such as in cases where a higher-layer protocol might provide error and flow control.UDP is the transport protocol for several well-known application-layer protocols,including Network File System (NFS), Simple Network Management Protocol (SNMP),Domain Name System (DNS), and Trivial File Transfer Protocol (TFTP).The UDP packet format contains four fields, as shown in the figure below. These includesource and destination ports, length, and checksum fields.A UDP packet consists of four fields.


Source and destination ports contain the 16-bit UDP protocol port numbers used todemultiplex datagrams for receiving application-layer processes. A length field specific the length of the UDP header and data. Checksum provides an (optional) integrity checkon the UDP header and data.





QUESTION 39:   DRAG DROPYou work as a network administrator at Certkiller .com.Your boss, Mrs. Certkiller, is interested in the OSI layers. Match the items with the appropriate layers. Note that not all options are used. 


Answer:  [image]


Certkiller is installing IP phones in a new office. The phones and office computersconnect to the same device. To ensure maximum throughout for the phone datasessions, the company needs to make sure that the phone traffic is on a differentnetwork from that of the office computer data traffic. What is the best networkdevice to which to directly connect the phones and computers and what technologyshould be implemented on this device?

(Choose two) A. VLANB. SubinterfaceC. STPD. HubE. SwitchF. RouterG. Wireless Access PointH. VTP
Answer: A, E
QUESTION 41:  The corporate head office of Certkiller has a teleconferencing system that uses VOIP(voice over IP) technology. This system uses UDP as the transport for the datatransmissions. If these UDP datagrams arrive at their destination out of sequence,what will happen? A. UDP will send an ICMP Information Request to the source host.B. UDP will pass the information in the datagrams up to the next OSI layer in the orderthat they arrive.C. UDP will drop the datagrams.D. UDP will use the sequence numbers in the datagram headers to reassemble the data inthe correct order.E. UDP will not acknowledge the datagrams and wait for a retransmission of thedatagrams.
Answer: B Explanation:  VOIP systems utilize UDP because it is faster and uses less overhead. In addition, thereliable transport mechanism used in TCP is useless to VOIP because if a packet gets dropped and needs to be resent, it will be already too late.UDP provides a service for applications to exchange messages. Unlike TCP, UDP isconnectionless and provides no reliability, no windowing, and no reordering of thereceived data. However, UDP provides some functions of TCP , such as data transfer,segmentation, and multiplexing using port numbers, and it does so with fewer bytes of overhead and with less processing required. UDP data transfer differs from TCP data 

Part of the Certkiller network is shown below:


You work as a network technician for Certkiller and are responsible for thisnetwork. Based on the diagram shown above, how many collision domains arethere?  A. SixB. FourteenC. FourD. TwoE. ThreeF. OneG. Eight   
Answer: D Explanation: 

The multi-segment configuration guidelines apply only to a single Ethernet "collision domain." A collision domain is formally defined as a single CSMA/CD network in whichthere will be a collision if two computers attached to the system transmit at the same time. An Ethernet system composed of a single segment or multiple segments linked withrepeaters is a network that functions as a single collision domain.

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