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若图8-20中路由器R1采用动态NAT-PT映射配置，其中IPv6网络中的任意节点动态映射到IPv4地址池10.3.2.211～10.3.2.220中的某个IP地址，IPv6网络上NAT-PT的操作使用的网络前缀为2011:2fc6:0:0:0:2::/96，则通过以下在路由器R1上的相关配置，IPv6网络中任意节点可以建立到IPv4网络中任意节点的会话。根据网络拓扑和需求说明，完成(或解释)路由器R1的相关配置。
R1 (config) # ipv6 access-list v6_net permit 2011:2fc6::/64 any (9)
R1 (config) # ipv6 (10) (声明在IPv6域内NAT-PT使用的IPv6前缀)
R1 (config) # ipv6 nat v6v4 pool ipv4_pool 10.3.2.211 10.3.2.220 prefix-length (11) (规定动态NAT-PT转换过程中使用的源IPv4地址池)
R1 (config) # ipv6 nat v6v4 source list (12) pool (13) (配置动态NAT-PT映射)
R1 (config) #

答案

参考答案：ipv4 pool

解析：在全局配置模式下，可以使用配置语句ipv6 access-list v6 net permit 2011:2fc6::/64 any配置一个名为v6 net的标准IPv6 ACL，以规定IPv6单协议网络中允许被转换的IPv6地址范围。
在全局配置模式下，可以使用配置语句ipv6 nat prefix ＜ipv6-address＞/96声明在IPv6域内NAT-PT使用的IPv6前缀。结合题干已给出的关键信息“IPv6网络使用NAT-PT网络前缀为2011:2fc6:0:0:0:1::/96”可得，(10)空缺处应填入natprefix 2011:2fc6:0:0:0:1::/96。
在全局配置模式下，可以使用配置语句ipv6 nat v6v4 pool ＜natpt-pool-name＞＜start-ipv4-address＞＜end-ipv4-address＞prefix-length＜prefix-length＞规定动态NAT-PT转换过程中使用的源IPv4地址池。结合题干已给出的关键信息“其中IPv6网络中的任意节点动态映射到IPv4地址池10.3.2.211～10.3.2.220中的某个IP地址”，以及图8-20中路由器R1的e0接口IP地址信息10.3.2.254/24可得，该源IPv4地址池的前缀长度为24位，即(11)空缺处应填入24。
在全局配置模式下，可以使用配置语句ipv6 nat v6v4 source＜list | route-map＞＜list-name | route-map-name＞pool＜natpt-pool-name＞[overload]配置动态NAT-PT映射。由配置语句ipv6access.list v6 net permit 2011:2fc6::/64 any可得，＜list-name＞应为v6 net，即(12)空缺处应填入v6_net。由配置语句ipv6 nat v6v4 pool ipv4_pool 10.3.2.211 10.3.2.220 prefix-length (11) 可得，＜natpt-pool-name＞应为ipv4 pool，即(13)空缺处应填入ipv4 pool。

填空题

已知A={1，0，-1，2}，B={y|y=|x|，x∈A}，则B=（    ）。
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单项选择题

It is said that in England death is pressing, in Canada inevitable and in California optional. Small wonder. Americans’ life expectancy has nearly doubled over the past century. Failing hips can be replaced, clinical depression controlled, cataracts removed in a 30-minute surgical procedure. Such advances offer the aging population a quality of life that was unimaginable when I entered medicine 50 years ago. But not even a great health-care system can cure death—and our failure to confront that reality now threatens this greatness of ours.

Death is normal; we are genetically programmed to disintegrate and perish, even under ideal conditions. We all understand that at some level, yet as medical consumers we treat death as a problem to be solved. Shielded by third-party payers from the cost of our care we demand everything that can possibly be done for us, even if it’s useless. The most obvious example is latestage cancer care. Physicians—frustrated by their inability to cure the disease and fearing loss of hope in the patient—too often offer aggressive treatment far beyond what is scientifically justified.

In 1950, the U. S. spent $12.7 billion on health care. In 2002, the cost will be $1,540 billion. Anyone can see this trend is unsustainable. Yet few seem willing to try to reverse it. Some scholars conclude that a government with finite resources should simply stop paying for medical care that sustains life beyond a certain age—say 83 or so. Former Colorado governor Richard Lamm has been quoted as saying that the old and infirm "have a duty to die and get out of the way" so that younger, healthier people can realize their potential.

I would not go that far. Energetic people now routinely work through their 60s and beyond, and remain dazzlingly productive. At 78 Viacom chairman Sumner Redstone jokingly claims to be 53. Supreme Court Justice Sandra Day O’Connor is in her 70s, and former surgeon general C. Everett Koop chairs an Internet start-up in his 80s. These leaders are living proof that prevention works and that we can manage the health problems that come naturally with age. As a mere 68-year-old, I wish to age as productively as they have.

Yet there are limits to what a society can spend in this pursuit. As a physician, I know the most costly and dramatic measures may be ineffective and painful. I also know that people in Japan and Sweden, countries that spend far less on medical care, have achieved longer, healthier lives than we have. As a nation we may be overfunding the quest for unlikely cures while underfunding research on humbler therapies that could improve people’s lives.

What is implied in the first sentence().

A. Americans are better prepared for death than other people.

B. Americans enjoy a higher life quality than ever before.

C. Americans are over-confident of their medical technology.

D. Americans take a vain pride in their long life expectancy.
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