思科认证考试（Cisco）CCNA考试七十九题(8)

 

 

71. Which layer is responsible for providing mechanisms for multiplexing
upper-layer application, session establishment, and tear-down of virtual circuits?

A. Application B. Presentation C. Session D. Transport

Answer D.

72. Which layer is responsible for coordinating communication between systems?

A. Application B. Presentation C. Session D. Physical

Answer C.

73. Which layer is responsible for negotiating data transfer syntax?

A. application B. presentation C. session D. transport

Answer B.

74. Which of the following is a characteristic of a switch, but not of a repeater?

A. Switches forward packets based on the IPX or IP address in the frame.
B. Switches forward packets based only on the IP address in the packet.
C. Switches forward packets based on the IP address in the frame
D. Switches forward packets based on the MAC address in the frame

Answer D. Switches are network device that filters, forwards, and floods frames
based on the destination address of each frame. The switch operates at the data
link layer of the OSI model. Switches use layer 2 addresses to filter the network

75. How does the cut-through switching technique work?

A. The LAN switch copies the entire frame into its buffers and then looks up the
destination address in its forwarding, table and determines the outgoing interface
B. The switch waits only for the header to be received before it checks the
destination address and starts forwarding the packets
C. By using broadcast addresses as source addresses
D. By using a Class II repeater in a collision domain

Answer B. Packet switching approach that streams data through a switch so that the
leading edge of a packet exits the switch at the output port before the packet
finishes entering the input port. A device using cut-through packet switching
reads, processes, and forwards packets as soon as the destination address is looked
up, and the outgoing port determined. Also known as on-the-fly packet switching.

76. How do switches use store and forward?

A. The switch waits only for the header to be received before it checks the
destination address and starts forwarding the packets
B. The LAN switch copies the entire frame into its buffers and then looks up the
destination address in its forwarding, table and determines the outgoing interface
C. By using a class II repeater in a collision domain
D. By using broadcast addresses as source addresses

Answer B. Packet-switching technique in which frames are completely processed
before being forwarded out the appropriate port. This processing includes
calculating the CRC and checking the destination address. In addition, frames must
be temporarily stored until network resources (such as an unused link) are
available to forward the message. Contrast with cut-through packet switching.

77. Choose all of the following that are needed to support full-duplex Ethernet.

A. Multiple paths between multiple stations on a link
B. Full-duplex NIC cards
C. Loop back and collision detection disabled
D. Automatic detection of full-duplex operation by all connected stations

Answer B C. Capability for simultaneous data transmission between a sending station
and a receiving station.

78. What two types of technology does 100BaseT use?

A. Switching with 53-byte cells
B. CSMA/CD
C. IEEE 802.5
D. 802.3u

Answer B D. 100-Mbps baseband Fast Ethernet specification using UTP wiring. Like
the 10BaseT technology on which it is based, 100BaseT sends link pulses over the
network segment when no traffic is present. However, these link pulses contain more
information than those used in 10BaseT. Based on the IEEE 802.3 standard.

79. Choose all of the following that are advantages to segmenting with routers.

A. Manageability
B. Flow control
C. Explicit packet lifetime control
D. Multiple active paths

Answers A, B, C, D. All of the above is correct. A router is a Network layer device
that uses one or more metrics to determine the optimal path along which network
traffic should be forwarded. Routers forward packets from one network to another
based on network layer information