CCNA QUESTIONS

Topic 1, DESCRIBE HOW A NETWORK WORKS

questions)
Section 1: Describe the purpose and functions of various network
devices (10 questions)

QUESTION NO: 1
Both switches and hubs are being utilized within the TestKing network. Which of
the following is true regarding the use of switches and hubs for network
connectivity in this network?

A. Switches take less time to process frames than hubs take
B. Hubs can filter frames
C. Switches do not forward broadcasts
D. Switches increase the number of collision domains in the network
E. Using hubs can increase the amount of bandwidth available to hosts
F. None of the above

Answer: D
Explanation:
The biggest benefit of using switches instead of hubs in your internetwork is that each
switch port is actually its own collision domain. (Conversely, a hub creates one large
collision domain.) But even armed with a switch, you still can't break up broadcast
domains. Neither switches nor bridges will do that. They'll typically simply forward all
broadcasts instead. Switch creates the collision domain per port, so we can say switch
increase the number of collision domains.




QUESTION NO: 2

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 broadcast
D. Switches are more efficient than hubs in processing frames.
E. Switches increase the number of collision domains in the network.


Answer: E


Explanation: 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.
Incorrect Answers:
A. Switches are capable of VLAN configurations, but hubs are not.
B. Hubs are generally the least costly method possible to connect multiple devices
together in a network.
C. Switches forward broadcasts and multicasts, by default, to all ports within the same
VLAN. Only routers block all broadcast traffic by default.
D. Switches and hubs can be equally efficient in processing frames, in theory. In practice,
switches are generally more efficient as they usually have more CPU and memory
allocated to them, and are generally much more expensive than a simple hub.


QUESTION NO: 3

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.
Incorrect Answers:

a. Switches are generally faster than bridges. Bridges also do not necessarily have fewer
ports than switches.
D. Both bridges and switches will forward broadcast and multicast traffic, assuming that
the traffic remains in the same VLAN.
E. The use of VLANs in a switch can decrease the size of the collision domain, by
creating additional, smaller collision domains.

QUESTION NO: 4

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.

Incorrect Answers:
B. Routers can indeed be used to segment a network separate a collision domain, since
routers do not forward LAN broadcasts and multicasts to other interfaces. However,
routers alone can not prevent all collisions from occurring on any given LAN segment.
D. Routers actually segment LANs into smaller broadcast domains.
E. Routers do not forward broadcast and multicast traffic out the additional interfaces by
default. Unless bridging or IP helpers are configured on the router, LAN broadcasts are
blocked at the router level.
QUESTION NO: 5


The LAN needs are expanding at the Testking corporate office, which is quickly
growing. You are instructed to enlarge the area covered by a single LAN segment on
the TestKing 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 NO: 6
Cisco is the leader in the router market space. What basic functions do their routers
perform in a network? (Choose two)


A. The micro-segmentation 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:
Leading the way in IT testing and certification tools, www.testking.com
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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.

QUESTION NO: 7
Both bridges are switches are being used throughout the TestKing LAN. Which of
the following statements are true regarding bridges and switches in this network?
(Choose 3)


A. Switches are primarily software based while bridges are hardware based.
B. Switches usually have a higher number of ports than most bridges.
C. Bridges are frequently faster than switches.
D. Bridges define broadcast domains while switches define collision domains.
E. Both bridges and switches forward Layer 2 broadcasts.
F. Both bridges and switches make forwarding decisions based on Layer 2 addresses.

Answer: B, E, F

QUESTION NO: 8
As a network administrator, you will need to decide on the appropriate network
devices to use. Which of the following correctly describes the roles of devices in a
WAN? (Choose three)

A. A CSU/DSU terminates a digital local loop.
B. A router is commonly considered a DCE device.
C. A modem terminates an analog local loop.
D. A router is commonly considered a DTE device.
E. A modem terminates a digital local loop.
F. A CSU/DSU terminates an analog local loop.
G. A modem is used to terminate a T1

Answer: A, C, D

Explanation:
Layer 2 switching is considered hardware-based bridging because it uses specialized
hardware called an application-specific integrated circuit (ASIC). ASICs can run up to
gigabit speeds with very low latency rates.
Switches usually have higher port number then bridge. Generally bridges have two ports.
Both operates on Data link layer.

QUESTION NO: 9
The TestKing network administrator needs to determine what LAN devices to
install on the TestKing 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 NO: 10
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

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



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

QUESTION NO: 11

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

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

.
QUESTION NO: 12

You download a file from an FTP site on the Internet. What is the highest layer in the
OSI model used in this FTP operation?

A. Application
B. Presentation
C. Session
D. Transport
E. Internet
F. Data Link
G. Physical

Answer: A

Explanation:
Layer 7 is the application layer, which is the highest layer in the OSI model. This layer
describes the use of end user applications, such as opening movie files (avi, mpeg, etc)
used Microsoft Office applications, using WWW browsers, using Telnet, and using FTP.


QUESTION NO: 13

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

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

QUESTION NO: 14

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

Explanation:
A key function of the transport layer is to provide connection services for the protocols
and applications that run at the levels above it. These can be categorized as either
connection-oriented services or connectionless services. Some protocol suites, such as
TCP/IP, provide both a connection-oriented and a connectionless transport layer protocol,
to suit the needs of different applications.
The transport layer is also the place in the layer stack where functions are normally
included to add features to end-to-end data transport. Where network layer protocols are
normally concerned with just "best effort" communications, where delivery is not
guaranteed. Transport layer protocols are given intelligence in the form of algorithms that
ensure that reliable and efficient communication between devices takes place. This
encompasses several related jobs, including lost transmission detection and handling, and
managing 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 so
important that some networking references define the transport layer on the basis of
reliability and flow-control functions. However, not all transport layer protocols provide
these services. Just as a protocol suite may have a connection-oriented and a
connectionless transport layer protocol, it may also have one that provides reliability and
data 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.

QUESTION NO: 15

At which OSI layer is a logical path created between two host systems named TK1
and TK2 on the TestKing LAN?

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

Answer: E


Explanation:
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.

QUESTION NO: 16

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

Explanation:
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.

QUESTION NO: 17

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

A. Application
B. Presentation
C. Session
d. transport
E. Network
F. Data link
G. Physical

Answer: E

Explanation:
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.

QUESTION NO: 18

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
link.
B. The transport layer divides a data stream into segments and adds reliability and flow
control 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
segment.
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

Explanation:
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:
The Network Layer:
Layer three of the OSI model is the network layer.
network.
packets.

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.

QUESTION NO: 19

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

Explanation:
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)

QUESTION NO: 20

Network equipment supporting the use of flow control mechanisms has been
recently installed in the TestKing 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

Explanation:
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.
D. The maximum transmission unit (MTU) handles the regulation of maximum frame
sizes.

QUESTION NO: 21
A receiving host on the TestKing network named TK1 computes the checksum on a
frame and determines that the frame is damaged. The frame is then discarded. At
which OSI layer did this happen?

A. Application
B. Presentation
C. Session
D. Transport
E. Internet
F. Data Link
G. Physical

Answer: F
Explanation:
The Data Link layer provides the physical transmission of the data and handles error
notification, network topology, and flow control. The Data Link layer formats the
message into pieces, each called a data frame, and adds a customized header containing
the hardware destination and source address. Protocols Data Unit (PDU) on Datalink
layer is called frame. According to this question the frame is damaged and discarded
which will happen at the Data Link layer

QUESTION NO: 22

Which protocol below uses TCP port 443 at layer 4?
A. HTML
B. HTTPS
C. TFTP
D. Telnet
E. SMTP
F. None of the above

Answer: B

Explanation:
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.

QUESTION NO:23

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)
A. TCP
B. Telnet
C. FTP
D. Ping
E. IP
F. UDP

Answer: B, C

Explanation:
The application layer is the top layer of the OSI model and is used to describe the end
user applications that can be used over a network.
Layer Name Examples
Application (layer 7) Telnet, HTTP, FTP, WWW browsers, NFS, SMTP gateways,
SNMP

Incorrect 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).




QUESTION NO: 24

As the TestKing 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 point
for communications devices. A layered approach is used to segment the entire
telecommunications process into a series of smaller steps.
A is correct because it encourages a level of standardization by encouraging that functions
be compared to known layers. D is also correct because it allows engineers to focus on
the development, refining, and perfection of simpler components.

QUESTION NO: 25

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

QUESTION NO: 26

Which of the protocols below use TCP at the transport layer? (Select four)
A. TFTP
B. SMTP
C. SNMP
D. FTP
E. HTTP
F. HTTPS

Answer: B, D, E, F

Explanation:
SMTP (Simple Mail Transfer Profile for email), FTP (File Transfer Protocol), and
HTTP/HTTPS (Hyper Text Transfer Protocol for internet) all use TCP because of the
reliable 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.



QUESTION NO: 27

Which fields are included in the TCP header? (Choose three).

A. Source Port
B. Acknowledgement Number
C. Request Number
D. Destination Address
E. Window
F. Data

Answer: A, B, E

Explanation:
TCP header:
Source Port: 16 bits.
Destination Port: 16 bits.
Sequence Number: 32 bits.
The sequence number of the first data byte in this segment. If the SYN bit is set, the
sequence number is the initial sequence number and the first data byte is initial sequence
number + 1.
Acknowledgment Number: 32 bits.
If the ACK bit is set, this field contains the value of the next sequence number the sender
of the segment is expecting to receive. Once a connection is established this is always
sent.
Data Offset: 4 bits.
The number of 32-bit words in the TCP header. This indicates where the data begins. The
length of the TCP header is always a multiple of 32 bits.
Reserved: 3 bits.
Must be cleared to zero.
ECN, Explicit Congestion Notification: 3 bits.
Added in RFC 3168.
Control Bits: 6 bits.
Window: 16 bits, unsigned.
The number of data bytes beginning with the one indicated in the acknowledgment field
which the sender of this segment is willing to accept.
Checksum: 16 bits.
This is computed as the 16-bit one's complement of the one's complement sum of a
pseudo header of information from the IP header, the TCP header, and the data, padded as
needed with zero bytes at the end to make a multiple of two bytes.
Urgent Pointer: 16 bits, unsigned.


If the URG bit is set, this field points to the sequence number of the last byte in a
sequence of urgent data.
Options: 0 to 44 bytes.
Options occupy space at the end of the TCP header. All options are included in the
checksum. An option may begin on any byte boundary. The TCP header must be padded
with zeros to make the header length a multiple of 32 bits.
Data: Variable length.

QUESTION NO: 28

Acknowledgements, sequencing, and flow control are functions that are handled by
which 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

QUESTION NO: 29

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 a
sender 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 window
size of 64 KB (kilobytes), the sender can only send 64 KB of data and then it must stop
and wait for an acknowledgment from the receiver that some or all of the data has been
received. If the receiver acknowledges that all the data has been received then the sender
is free to send another 64 KB.
One way to improve the reliability of the TCP connection is to reduce the window size
that the receiver needs to receive before sending an acknowledgement. However, this will
reduce throughput as more segments and acknowledgements will need to be sent in order
to transfer the same amount of data.

QUESTION NO: 30

You have set up an Internet based FTP server, where people can upload and
download files. In terms of the OSI model, what is the highest layer used during the
FTP 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 for
end 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 point
but they are incorrect because the question asked for the highest layer used by FTP.

QUESTION NO: 31

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 or
whether a remote site is reachable. This tool is a common network tool for determining
the network connectivity which uses ICMP protocol instead of TCP/IP and UDP/IP. This
protocol is usually associated with the network management tools which provide network
information to network administrators, such as ping and traceroute (the later also uses the
UDP/IP protocol).
ICMP is quite different from the TCP/IP and UDP/IP protocols. No source and
destination ports are included in its packets. Therefore, usual packet-filtering rules for
TCP/IP and UDP/IP are not applicable. Fortunately, a special "signature" known as the
packet's Message type is included for denoting the purposes of the ICMP packet. Most
commonly used message types are namely, 0, 3, 4, 5, 8, 11, and 12 which represent echo
reply, destination unreachable, source quench, redirect, echo request, time exceeded, and
parameter problem respectively.
In the ping service, after receiving the ICMP "echo request" packet from the source
location, the destination
Incorrect Answers
ICMP is an IP protocol so A and E are incorrect.
ICMP doesn't guarantee datagram delivery so B is wrong as well.

QUESTION NO: 31

Which of the following services use TCP? (Choose three)

A. DHCP
B. SMTP
C. SNMP
D. FTP
E. HTTP
F. TFTP


Answer: B, D, E

Explanation:

TCP (Transmission Control Protocol) is a reliable mechanism for data delivery. SMTP,
FTP and HTTP services use TCP via ports 25, 20/21, and 80, respectively.

QUESTION NO: 32

Which of the following are types of flow control? (Choose three)
A. Buffering
B. Cut-through
C. Windowing
D. Congestion avoidance
E. Load balancing

Answer: A, C, D

Explanation:
Data transmission flow control occurs at layer 4 with the help of buffering, windowing
and congestion avoidance.

QUESTION NO: 33

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

A. IP
B. ICMP
C. DNS
D. TCP
E. UDP
F. RTP

Answer: D

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

QUESTION NO: 34

FTP, Telnet, DNS, and SMTP are all protocols being used in the TestKing network.
Of these, which uses both TCP and UDP ports?

A. Telnet
B. FTP
C. DNS
D. SMTP
E. None of the above

Answer: C

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

QUESTION NO: 35

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 a
UDP header? (Choose three)

A. Checksum
B. Sequence number
C. Destination port
D. Window size
E. Acknowledgment number
F. Source port

Answer: B, D, E

Explanation:
Twelve fields comprise a TCP packet.
TCP Packet Field Descriptions
The 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 and
destination processes receive TCP services.
2. Sequence Number-Usually specifies the number assigned to the first byte of data in the
current message. In the connection-establishment phase, this field also can be used to
identify an initial sequence number to be used in an upcoming transmission.
3. Acknowledgment Number-Contains the sequence number of the next byte of data the
sender 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 used
for 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 space
available 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 and
upper-layer processes. UDP protocol ports distinguish multiple applications running on a
single 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 less
network 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 include
source 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 to
demultiplex datagrams for receiving application-layer processes. A length field specifies
the length of the UDP header and data. Checksum provides an (optional) integrity check
on the UDP header and data.




QUESTION NO:36

What is the purpose of an Address Resolution Protocol (ARP) request message?

A. It creates a session by passing a header with destination Layer 2 address to the
transport layer.
B. It binds the IP address of a host to the network that it is on.
C. It encapsulates the Layer 3 address and then passes the packet to Layer 2.
D. It builds a correlation between an IP address and a MAC address.
E. It provides connectivity and path selection between hosts on a network.
F. None of the above

Answer: D

Explanation:
Address Resolution Protocol (ARP) finds the hardware address of a host from a known IP
address. When IP has a datagram to send, it must inform a Network Access protocol, such
as Ethernet or Token Ring, of the destination's hardware address on the local network. (It
has already been informed by upper-layer protocols of the destination's IP address.) If IP
doesn't find the destination host's hardware address in the ARP cache, it uses ARP to find
this information.
This is the protocol operates on Network Layer. Source device sends the ARP broadcast
to resolve the MAC address of destination device.
You can display the ARP table using the "show arp" command.