思科认证

思科认证:CCNA认证模拟试题练习及答案83

时间: 2013-10-10
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


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