CCNA 640-802 Ver 22-09-2008 page3
QUESTION 21
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 22
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 23
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:
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 network. 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 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 24
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)
Sequenced Packet Exchange (SPX) A reliable communications protocol created by Novell NetWare
QUESTION 25
DRAG DROP
You 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.
Answer :
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
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.
QUESTION 27
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
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 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
QUESTION 29
You have just installed a new web server on the Certkiller 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:
Certkiller (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
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.
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 22
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 23
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:
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 network. 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 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 24
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)
Sequenced Packet Exchange (SPX) A reliable communications protocol created by Novell NetWare
QUESTION 25
DRAG DROP
You 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.
Answer :
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
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.
- SourcePort and DestinationPort-Identifies points at which upper-layer source and destination processes receive TCP services.
- 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.
- Acknowledgment Number-Contains the sequence number of the next byte of data the sender of the packet expects to receive.
- Data Offset-Indicates the number of 32-bit words in the TCP header.
- Reserved-Remains reserved for future use.
- 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.
- Window-Specifies the size of the sender's receive window (that is, the buffer space available for incoming data).
- Checksum-Indicates whether the header was damaged in transit.
- Urgent Pointer-Points to the first urgent data byte in the packet.
- Options-Specifies various TCP options.
- Data-Contains upper-layer information.
QUESTION 27
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
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 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
QUESTION 29
You have just installed a new web server on the Certkiller 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:
Certkiller (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
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.
==========================================================
