New CCNA 640-802 Question Answer 3
QUESTION 25:
DRAG DROP
You work as a network administrator at Certifyme .com.
Your boss, Mrs. Certifyme, 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 located
in 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 and can establish a logical connection between the sending host and destination host on an internetwork.
TCP and UDP transport protocol lies on Transport Layer, which break down the data
coming from upper layer into segment.
Windows are used to control the amount of outstanding, unacknowledged data segments that is also on Transport Layer.
Network Layer:
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.
Protocol Data Packets (PDU) on Network Layer is known as Packets. Routing and
Routed protocols are lies on Network Layer.
Routing Protocol: RIP, IGRP, EIGRP, OSPF, BGP Routed Protocol: IP, IPX
QUESTION 26:
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
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Explanation:
The Figure below illustrates the fields and overall format of 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 and destination processes receive TCP services.
2.
3. 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.
4.
5. Acknowledgment Number-Contains the sequence number of the next byte of data the sender 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 a
variety of control information, including the SYN and ACK bits used for connection establishment, and the FIN bit used for connection termination.
12.
13. Window-Specifies the size of the sender’s receive window (that is, the buffer space available 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.
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QUESTION 27:
Network equipment supporting the use of flow control mechanisms has been
recently installed in the Certifyme 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 28:
Part of the Certifyme network is displayed below:
Study the exhibit shown above. Host Certifyme A has established a connection with the Certifyme II server attached to interface E0 of the Certifyme 2 router. Which of the following statements describe the information contained in protocol data units
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sent from Host Certifyme to Certifyme 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
Certifyme 1 router
C. The destination IP address of a packet will be the IP address of the network interface
of the Certifyme II server
D. The destination address of a frame will be the MAC address of the E0 interface of
Certifyme 1 router Answer: A, C, D QUESTION 29:
You have just installed a new web server on the Certifyme network. You are required
to ensure that the web server is accessible from the Internet. The network uses private addressing, so an IP-to-registered address mapping is required.
To do this, you enter the following command:
Certifyme (config)# ip nat inside source static 192.168.2.1
198.18.1.254
You unsuccessfully try to ping the Internet from a PC host on the LAN. During the troubleshooting process, you enter the “show ip nat translations” command but the output is blank.
What is the most likely cause of the problem?
A. The keyword overload is missing from the command. B. The NAT pool must be defined first.
C. An access list must be defined to create static NAT translations. D. The interfaces must be configured for NAT.
E. None of the above
Answer: D Explanation:
In order to successfully configure a static NAT translation, the interfaces must be configured for NAT, in addition to the global NAT command that was entered. The router interface that lies on the inside part of the network must be defined using the “ip nat inside” command. Similarly, the WAN interface that is being used for the Internet connection must be defined using the “ip nat outside” command.
Incorrect Answers:
A. In order to make an internal server reachable from the Internet, a static one to one NAT entry must be configured for the server. The keyword “overload” is used to configure many to one NAT, or PAT.
B, C. This need not be done in order to create a static NAT entry. These steps are
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typically done in setting up NAT so that inside LAN users can access the Internet via
NAT.
QUESTION 30:
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 31:
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.
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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).
Reference: CCNA Self-Study CCNA INTRO exam certification Guide (Cisco Press, ISBN 1-58720-094-5) Page 34.
QUESTION 32:
As the Certifyme 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 33:
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
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D. Buffering
E. Load Balancing
F. Fast Forward Answer: A, B, D QUESTION 34:
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.
Reference: CCNA Self-Study CCNA INTRO exam certification Guide (Cisco Press,
ISBN 1-58720-094-5) Page 163.
QUESTION 35:
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.
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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 TCP
header. 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.
By dfd, September 3, 2008 @ 1:17 pm
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By killer, September 6, 2008 @ 1:10 am
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