问题 单项选择题

如图7-2所示,网络站点A发送数据包给站点B,当路由器R1将数据包转发给路由器R2时,被转发数据包中封装的源IP地址和目的MAC地址分别是()。

A.222.4.56.2,00-d0-02-85-cd-3f

B.222.4.57.1,00-ff-2a-3a-4b-5b

C.222.4.57.1,00-ff-2a-3a-4b-5b

D.222.4.56.1,00-d0-02-85-cd-3f

答案

参考答案:A

解析:

[考点透解] 在如图7-2所示的拓扑结构中,网络站点A发送数据包给站点B,其数据帧中源MAC地址、目的MAC地址、源IP地址和目的IP地址在各个网络位置的参数变化情况如表7-6所示。

表7-6 站点A所发数据帧相关地址参数表
所在网络位置目的MAC地址源MAC地址目的IP地址源IP地址
站点A至路由器R1的Port1端口00-d0-02-85-a7-f000-20-e0-8c-0d-7e222.4.59.2222.4.56.2
路由器R1的Port2端口至路由器R2的Portl端口00-d0-02-85-cd-3f00-d0-02-85-b7-0f222.4.59.2222.4.56.2
路由器R2的Port2端口至站点B00-ff-2a-3a-4b-5b00-d0-02-86-c7-f6222.4.59.2222.4.56.2

由表7-6可知,在数据分组通过每一个路由器转发时,分组中的目的MAC地址、源MAC地址参数是变化的,但它的目的IP地址、源IP地址、目的端口号等参数是始终不变的。当路由器R1将数据包转发给路由器R2时,被转发数据包中封装的源IP地址为222.4.56.2,目的MAC地址为00-d0-02-85-cd-3f。

单项选择题 A1型题
单项选择题

Most critical plot points in Harry Potter and the Sorcerer’s Stone came from J. K. Rowling’s imagination, but Flamel and his powerful pebble were legendary long before Harry went to Hogwarts. The 14th century alchemist created the philosoper’s stone (called "sorcerer’s" in U.S.editions of Potter ), with which he turned mercury to gold and gained eternal life. But Flamel’s tale—like his stone and his science—was no more real than a magic.

The philosopher’s stone was the key to alchemy, the medieval predecessor to chemistry that aimed to cure all illnesses, make the elixir of life, and transmute base metals into gold. The last made perfect sense at the time. The Aristotelian theory of elements stated that all things consisted of fire, air, water, and earth. So a little shift in one metal’s composition could create gold.

Flamel was renowned as an alchemical success. In 1382, after 25 years of studying an ancient book by "Abraham the Jew", he is said to have produced the philosopher’s stone. His texts, notably a deconstruction of the "Abraham" work, were standard reading for aspiring scientists like Isaac Newton.

Many alchemists believed Flamel faked his 1418 death and that of his wife. Rumored sightings in the 18th century placed them at the Paris Opera. As late as 1816 there were reports of people searching Flamel’s former house for secrets of the stone.

Contemporary historians say, a Nicolas Flamel did live in Paris in the 1300s and endowed many churches and hospitals with his wealth. But he was no alchemist. "He got his money in pedestrian ways—his wife’s earlier marriages, real-estate speculation," says lawrence Principe, author of The Aspiring Adept. Anachronisms, style of language, and the lack of earlier copies indicate that none of "his" writings originated prior to the 1500s.

"This sort of thing happens in alchemy," says Bill Newman, author of alchemical history Gehennical Fire. When an alchemist couldn’t back up his ideas, he might publish them in the guise of a "lost" work. Flamel’s wealth made a good candidate for alchemical identity theft.

Flamel writings and sightings faded with alchemy’s prestige. And the closest anyone’s come to the philosopher’s stone is Rowling. In her hands, it has yielded not just gold but eternal (shelf) life as well.

The last sentence of Paragraph 6, "Flamel’s wealth" identity theft. " implies that (). "

A. Flamel’s wealth and his fame was exploited to promote alchemy

B. Flamel’s made his fortune by deceiving all people including his wife

C. Flamel’s pretended to be an alchemist and earned his living by that

D. Flamel’s success in alchemy had much to do with his wealth