问题 单项选择题

主机A运行UNIX操作系统,IP地址为202.113.224.35,子网屏蔽码为255.255.255.240;主机B运行Linux操作系统,IP地址为202.113.224.38,子网屏蔽码为255.255.255.240。它们分别被连接在同一台局域交换机上,但处于不同的VLAN中。主机A通过ping命令去ping主机B时,发现接收不到正确的响应。请问可能的原因是______。

A.主机A和主机B的IP地址不同

B.主机A和主机B处于不同的VLAN中

C.主机A和主机B使用了不同的操作系统

D.主机A和主机B处于不同的子网中

答案

参考答案:B

解析: 本题考查点是同一虚拟局域网中广播信息测试。一个虚拟局域网(VLAN)就是一个逻辑工作组。同一逻辑工作组内的成员,其物理位置可以处于同一物理网络,也可以处于不同的物理网络,但是逻辑上可以像在同一局域网中一样“广播”数据,而不同逻辑工作组内的成员则不能接收该广播数据。这正是利用虚拟局域网隔离广播风暴,减少广播数据流量和提高网络内部安全性的原因。在虚拟局域网的管理中,常使用ping命令来检验VLAN之间的通信情况,同一个VLAN中的主机可以互相ping通,而不同VLAN中的主机则无法互相ping通。因此当处于不同的VLAN中主机A通过ping命令去pmg主机B时,是无法接收到正确响应的。

阅读理解

阅读理解

    The garden city was largely the invention of Ebenezer Howard (1850-1928). After immigrating from

England to the USA, and an unsuccessful attempt to make a living as a farmer, he moved to Chicago,

where he saw the reconstruction of the city after the disastrous fire of 1871.In those days, it was

nicknamed "the   Garden City",almost certainly the source of Howard's name for his later building plan

of towns.Returning to  London, Howard developed his design in the 1880s and 1890s, drawing_on ideas

that were popular at the time, but creating a unique combination of designs.

      The nineteenthcentury poor city was in many ways a terrible place, dirty and crowded; but it offered

economic and social opportunities.At the same time, the British countryside was in fact equally unattractive: though it promised fresh air and nature, it suffered from agricultural depression(萧条) and it offered neither enough work and wages, nor much social life.Howard's idea was to combine the best of town and country in a new kind of settlement,the garden city.Howard's idea was that a group of people should set up a

company, borrowing money to establish a garden city in the depressed countryside, far enough from

existing cities to make sure that the land was bought at the bottom price.

     Garden cities would provide a central public open space, radial avenues and connecting industries.

They would be surrounded by a much larger area of green belt, also owned by the company, containing

not merely farms but also some industrial institutions.As more and more people moved in, the garden city would reach its planned limit-Howard suggested 32,000 people; then, another would be started a short

distance away.Thus, over time, there would develop a vast planned house collection, extending almost

without limit; within it, each garden city would offer a wide range of jobs and services, but each would

also be connected to the others by a rapid transportation system,thus giving all the economic and social

opportunities of a big city.

1. How did Howard get the name for his building plan of garden cities?

A. Through his observation of the country life.

B. Through the combination of different ideas.

C. By taking other people's advice.

D. By using the nickname of the reconstructed Chicago.

2. The underlined phrase "drawing on" in Paragraph 1 probably means________.

A. making use of  

B. making comments on

C. giving an explanation of  

D. giving a description of

3. According to Howard, garden cities should be built______.

A. as far as possible from existing cities

B. in the countryside where the land was cheap

C. in the countryside where agriculture was developed

D. near cities where employment opportunities already existed

4. What can we learn about garden cities from the last paragraph?

A. Their number would continue to rise.

B. Each one would continue to become larger.

C. People would live and work in the same place.

D. Each one would contain a certain type of business.

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