题库V104.4_QUESTION 74 错误

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QUESTION 74

A national retail chain needs to design an IP addressing scheme to support a nationwide network. The

company needs a minimum of 300 sub-networks and a maximum of 50 host addresses per subnet.Working with

only one Class B address, which of the following subnet masks will support an appropriate addressing scheme?

(Choose two.)

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A. 255.255.255.0             256 subnets   254 hosts

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B. 255.255.255.128           512           126

C. 255.255.252.0             64            1022

D. 255.255.255.224           2048          30

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E. 255.255.255.192           1024          62

F. 255.255.248.0             32            2046

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根据题目描述一个B类网络子网划分后满足：最小300个子网，最大50个主机。

我算出了每个选项的结果，添加在后面，结果很直观，只有D选项正确.而题目答案却显示是BE,并且题目要求选择2个答案.

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我的疑问在题目描述“maximum of 50”,最大50 = 小于或者等于50。

而"minimum of 50",才是最小50，最小50 = 大于或者等于50。

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这是老外的观点：

http://www.9tut.com/ccna-subnetting

请看Question 3

注意：Notice: The question asks “The company needs a minimum of 300 sub-networks and a maximum of 50 host addresses per subnet” but this is a typo , you should understand it as “”The company needs a minimum of 300 sub-networks and a minimum of 50 host addresses per subnet”.

红色的typo,他也提到了这是排版错误.

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"maximum of 50 host addresses per subnet"

对于“Host address”，来自维基百科的解释：

http://en.wikipedia.org/wiki/Host_address

Host address
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The host address, or the host ID portion of an IP address, is the portion of the address used to identify hosts (any device requiring a Network Interface Card, such as a PC or networked printer) on the network. The network ID, by contrast, is the portion of the address that refers to the network itself.

Example:

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Your local network has an address of 192.168.1.0 /30 (using CIDR notation for this subnet).

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Your network ID is the first 30 bits, in bold below. The host portion is the last two bits. By changing those two bits, you can create the following IP addresses:

11000000.10101000.00000001.000000 00 (192.168.1.0, the network address)
: Q: S% n# c$ y5 f( R5 A11000000.10101000.00000001.000000 01 (192.168.1.1, the first usable address in the subnet)
- `- k  A; d# x2 ^6 @11000000.10101000.00000001.000000 10 (192.168.1.2, the last usable address in the subnet)
7 o8 A; t9 q; e1 O' E11000000.10101000.00000001.000000 11 (192.168.1.3, the broadcast address for the subnet)
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综上，host address 就是 host ID,是用来识别IP地址中的主机部分，并且是用2进制表示的。如上例中的“00”。

“maximum of 50 host addresses per subnet”这句话在逻辑上是有问题的。只能说“maximum of 50 hosts per subnet”

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结论：

要是这道题完美，必须将“maximum of 50 host addresses per subnet”改成：“minimum of 50 hosts per subnet.

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c4919654

默默等等楼下的回复

xxygq

可能是楼主英语比较好，，也有可能是题目排版错。
其他都不讲不管怎么理解 D绝对错的，就算排版是错的，D还是错。。，最大50个主机。 我49台行不行，，你选个D能放得下不？？？
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: N! G) Z6 q# a是这样理解的。
这个公司需要300个子网，每个子网最大主机数50台。现在有一个B类地址可供使用，下面哪两个子网掩码支持这个ip计划。  这样的话选BE很正常啊，子网数和主机数都符合要求。。。
, Z6 t5 p; Q; W, w8 ^. d我都没搞清楚楼主在纠结什么...

zdarkx

同意楼上的

卖男孩的小火柴

Mrchans

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