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2010-11-07 14:35:46
CCNA Sybex Ch1

CCNA Sybex Chap.1
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  1. 1. 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. Send a different source port number. B. Restart the virtual circuit. C. Decrease the sequence number. D. Decrease the window size.
    D. A receiving host can control the transmitter by using flow control (TCP uses Windowing by default). By decreasing the window size, the receiving host can slow down the transmitting host so the receiving host does not overflow its buffers.
  2. 2. Which fields are contained within an IEEE Ethernet frame header? (Choose two.) A. Source and destination MAC address B. Source and destination network address C. Source and destination MAC address and source and destination network address D. FCS field
    A, D. An Ethernet frame has source and destination MAC addresses, an Ether-Type field to identify the Network layer protocol, the data, and the FCS field that holds the answer to the CRC.
  3. 3. Which layer 1 devices can be used to enlarge the area covered by a single LAN segment? (Choose two.) A. Switch B. NIC C. Hub D. Repeater E. RJ45 transceiver
    C, D. Not that you really want to enlarge a single collision domain, but a hub (multiport repeater) will provide this for you.
  4. 4. Segmentation of a data stream happens at which layer of the OSI model? A. Physical B. Data Link C. Network D. Transport
    D. The Transport layer receives large data streams from the upper layers and breaks these up into smaller pieces called segments.
  5. 5. Which of the following describe router functions? (Choose four.) A. Packet switching B. Collision prevention C. Packet filtering D. Broadcast domain enlargement E. Internetwork communication F. Broadcast forwarding G. Path selection
    A, C, E, G. Routers provide packet switching, packet filtering, internetwork communication, and path selection.
  6. 6. Routers operate at layer __. LAN switches operate at layer __. Ethernet hubs operate at layer __. Word processing operates at layer __. A. 3, 3, 1, 7 B. 3, 2, 1, none C. 3, 2, 1, 7 D. 2, 3, 1, 7 E. 3, 3, 2, none
    B. Routers operate at layer 3. LAN switches operate at layer 2. Ethernet hubs operate at layer 1. Word processing applications communicate to the Application layer interface, but do not operate at layer 7, so the answer would be none.
  7. 7. When data is encapsulated, which is the correct order? A. Data, frame, packet, segment, bit B. Segment, data, packet, frame, bit C. Data, segment, packet, frame, bit D. Data, segment, frame, packet, bit
    C. The encapsulation method is data, segment, packet, frame, bit.
  8. 8. Why does the data communication industry use the layered OSI reference model? (Choose two.) A. It divides the network communication process into smaller and simpler components, thus aiding component development, design, and troubleshooting. B. It enables equipment from different vendors to use the same electronic components, thus saving research and development funds. C. It supports the evolution of multiple competing standards and thus provides business opportunities for equipment manufacturers. D. It encourages industry standardization by defining what functions occur at each layer of the model. E. It provides a framework by which changes in functionality in one layer require changes in other layers.
    A, D. The main advantage of a layered model is that it can allow application developers to change aspects of a program in just one layer of the layer model’s specifications. Advantages of using the OSI layered model include, but are not limited to, the following: It divides the network communication process into smaller and simpler components, thus aiding component development, design, and troubleshooting; it allows multiple-vendor development through standardization of network components; it encourages industry standardization by defining what functions occur at each layer of the model; it allows various types of network hardware and software to communicate; and it prevents changes in one layer from affecting other layers, so it does not hamper development.
  9. 9. What are two purposes for segmentation with a bridge? A. To add more broadcast domains B. To create more collision domains C. To add more bandwidth for users D. To allow more broadcasts for users
    B, C. Bridges break up collision domains, which allow more bandwidth for users.
  10. 10. Which of the following are unique characteristics of half-duplex Ethernet when compared to full-duplex Ethernet? (Choose two.) A. Half-duplex Ethernet operates in a shared collision domain. B. Half-duplex Ethernet operates in a private collision domain. C. Half-duplex Ethernet has higher effective throughput. D. Half-duplex Ethernet has lower effective throughput. E. Half-duplex Ethernet operates in a private broadcast domain.
    A, D. Unlike full duplex, half-duplex Ethernet operates in a shared collision domain, and it has a lower effective throughput than full duplex.
  11. 11. You want to implement a network medium that is not susceptible to EMI. Which type of cabling should you use? A. Thicknet coax B. Thinnet coax C. Category 5 UTP cable D. Fiber-optic cable
    D. Fiber-optic cable provides a more secure, long-distance cable that is not susceptible to EMI interference at high speeds.
  12. 12. Acknowledgments, sequencing, and flow control are characteristics of which OSI layer? A. Layer 2 B. Layer 3 C. Layer 4 D. Layer 7
    C. A reliable Transport layer connection uses acknowledgments to make sure all data is transmitted and received reliably. A reliable connection is defined by a virtual circuit that uses acknowledgments, sequencing, and flow control, which are characteristics of the Transport layer (layer 4).
  13. 13. Which of the following are types of flow control? (Choose all that apply.) A. Buffering B. Cut-through C. Windowing D. Congestion avoidance E. VLANs
    A, C, D. The common types of flow control are buffering, windowing, and congestion avoidance.
  14. 14. Which of the following types of connections can use full duplex? (Choose three.) A. Hub to hub B. Switch to switch C. Host to host D. Switch to hub E. Switch to host
    B,C,E.Hubs cannot run full-duplex Ethernet. Full duplex must be used on a point-to-point connection between two devices capable of running full duplex. Switches and hosts can run full duplex between each other, but a hub can never run full duplex.
  15. 15. What is the purpose of flow control? A. To ensure that data is retransmitted if an acknowledgment is not received B. To reassemble segments in the correct order at the destination device C. To provide a means for the receiver to govern the amount of data sent by the sender D. To regulate the size of each segment
    C. Flow control allows the receiving device to control the transmitter so the receiving device’s buffer does not overflow.
  16. 16. Which three statements are true about the operation of a full-duplex Ethernet network? A. There are no collisions in full-duplex mode. B. A dedicated switch port is required for each full-duplex node. C. Ethernet hub ports are preconfigured for full-duplex mode. D. In a full-duplex environment, the host network card must check for the availability of the network media before transmitting. E. The host network card and the switch port must be capable of operating in full-duplex mode.
    A, B, E. Full-duplex means you are using both wire pairs simultaneously to send and receive data. You must have a dedicated switch port for each node, which means you will not have collisions. Both the host network card and the switch port must be capable and set to work in full-duplex mode.
  17. 17. What type of RJ45 UTP cable is used between switches? A. Straight-through B. Crossover cable C. Crossover with a CSU/DSU D. Crossover with a router in between the two switches
    B. To connect two switches together, you would use a RJ45 UTP crossover cable.
  18. 18. How does a host on an Ethernet LAN know when to transmit after a collision has occurred? (Choose two.) A. In a CSMA/CD collision domain, multiple stations can successfully transmit data simultaneously. B. In a CSMA/CD collision domain, stations must wait until the media is not in use before transmitting. C. You can improve the CSMA/CD network by adding more hubs. D. After a collision, the station that detected the collision has first priority to resend the lost data. E. After a collision, all stations run a random backoff algorithm. When the backoff delay period has expired, all stations have equal priority to transmit data. F. After a collision, all stations involved run an identical backoff algorithm and then synchronize with each other prior to transmitting data.
    B, E. Once transmitting stations on an Ethernet segment hear a collision, they send an extended jam signal to ensure that all stations recognize the collision. After the jamming is complete, each sender waits a predetermined amount of time, plus a random time. After both timers expire, they are free to transmit, but they must make sure the media is clear before transmitting and that they all have equal priority.
  19. 19. What type of RJ45 UTP cable do you use to connect a PC’s COM port to a router or switch console port? A. Straight-through B. Crossover cable C. Crossover with a CSU/DSU D. Rolled
    D. To connect to a router or switch console port, you would use an RJ45 UTP rolled cable.
  20. 20. You have the following binary number: 10110111 What are the decimal and hexadecimal equivalents? A. 69/0x2102 B. 183/B7 C. 173/A6 D. 83/0xC5
    B. You must be able to take a binary number and convert it into both decimal and hexadecimal. To convert to decimal, just add up the 1s using their values. The values that are turned on with the binary number of 10110111 are 128 + 32 + 16 + 4 + 2 + 1 = 183. To get the hexadecimal equivalent, you need to break the eight binary digits into nibbles (4 bits), 1011 and 0111. By add- ing up these values, you get 11 and 7. In hexadecimal, 11 is B, so the answer is 0xB7.