【ciscoccna认证教程】CISCOCCNA认证考试640-810题库原题9

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your boss at testking asks you about half-duplex and full-duplex ethernet. what are unique for halfduplex   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.    

answer: a d   
explanation:   
a single device could not be sending a frame and receiving a frame at the same time because it would mean that a collision was occurring. so, devices simply chose not to send a frame while receiving a frame. that logic is  called half-duplex logic.   
ethernet switches allow multiple frames to be sent over different ports at the same time. additionally, if only  one device is connected to a switch port, there is never a possibility that a collision could occur. so, lan  switches with only one device cabled to each port of the switch allow the use of full-duplex operation. full   
duplex means that an ethernet card can send and receive concurrently.

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