QUESTION NO: 23
The IP network 210.106.14.0 is subnetted using a /24 mask. How many usable
networks and host addresses can be obtained from this?
IP地址210.106.14.0使用了一个/24的掩码,我们可以得到多少个可用网络和主机地址?

A. 1 network with 254 hosts
B. 4 networks with 128 hosts
C. 2 networks with 24 hosts
D. 6 networks with 64 hosts
E. 8 networks with 36 hosts

解析:本题很有趣,C类地址默认的就是/24的掩码,一个网段.

Answer: A

QUESTION NO: 24
Given that you have a class B IP address network range, which of the subnet masks
below will allow for 100 subnets with 500 usable host addresses per subnet?
给定一个B类地址,下列哪个掩码可以允许100个子网,每个子网500个可用主机地址

A. 255.255.0.0
B. 255.255.224.0
C. 255.255.254.0
D. 255.255.255.0
E. 255.255.255.224

解析:对于B类子网,默然掩码为255.255.0.0,如果每个子网需要500个主机地址,2的九次方=512,可见需要留给主机位为9位

Answer: C

QUESTION NO: 25
You have a class C network, and you need to design it for 5 usable subnets with
each subnet handling a minimum of 18 hosts each. Which of the following network
masks should you use?

你有一个C类网络,需要设置位5个子网,每个子网最少18台主机,下列哪个掩码可以做到这一点?

A. 225.225.224.0.
B. 225.225.240.0.
C. 225.225.255.0.
D. 255.255.255.224
E. 225.225.255.240

解析:本题思路同上题,每个子网18台主机,2的5次方=32,在最后的255里面留5位主机位便可.

Answer: D

不错不错,支持楼主.

真不错呢

UESTION NO: 26

The 213.115.77.0 network was subnetted using a /28 subnet mask. How many usable
subnets and host addresses per subnet were created as a result of this?

网络213.115.77.0被28位的子网掩码划分子网,可以得到多少个可用子网,每个子网多少可用主机?

A. 2 networks with 62 hosts
B. 6 networks with 30 hosts
C. 16 networks and 16 hosts
D. 62 networks and 2 hosts
E. 14 networks and 14 hosts
F. None of the above

解析:作为一个C类网络,默认掩码是/24,这回变成/28,可见借用了4位
可用子网数=2的4次方=16个
每个子网可用主机数=2的4次方-2=14个

Answer: F

QUESTION NO: 27
The 201.145.32.0 network is subnetted using a /26 mask. How many networks and
IP hosts per network exists using this subnet mask?

网络201.145.32.0被26位的子网掩码划分子网,可以得到多少个可用子网,每个子网多少可用主机?

A. 4 networks with 62 hosts
B. 64 networks and 4 hosts
C. 4 networks and 62 hosts
D. 62 networks and 2 hosts
E. 6 network and 30 hosts

解析:思路同上题
作为一个C类网络,默认掩码是/24,这回变成/26,可见借用了2位
可用子网数=2的2次方=4个
每个子网可用主机数=2的6次方-2=62个

Answer: C

QUESTION NO: 28
You have a class B network with a 255.255.255.0 mask. Which of the statements
below are true of this network? (Select all valid answers)
你有一个使用255.255.255.0掩码的B类网络,有关该网络说法正确的是哪些

A. There are 254 usable subnets.
B. There are 256 usable hosts per subnet.
C. There are 50 usable subnets.
D. There are 254 usable hosts per subnet.
E. There are 24 usable hosts per subnet.
F. There is one usable network.

解析:作为一个B类地址,默认掩码是255.255.0.0 这里变成了255.255.255.0,可见从主机位借用了8位用来划分子网
一共划分了2的8次方-2=254个,主机数目也是这样计算

答案:A,D

不错!~go on...

QUESTION NO: 29
How many usable IP addresses can you get from a conventional Class C address?
对于一个常规C类网络,我们可以得到多少个可用IP地址?

A. 128
B. 192
C. 254
D. 256
E. 510

答案:C

基础顾为重要！谢谢分享辛苦...

作为一个C类网络,默认掩码是/24,这回变成/26,可见借用了2位,可用子网数=2的2次方=4个
作为一个B类地址,默认掩码是255.255.0.0 这里变成了255.255.255.0,可见从主机位借用了8位用来划分子网,一共划分了2的8次方-2=254个

请问楼主，为什么b类地址的子网计算 是2的n次方-2，而c类地址可以不用-2呢？

晕..英语不好!

引用:

原帖由 hfj800625 于 2007-6-21 11:15 发表
作为一个C类网络,默认掩码是/24,这回变成/26,可见借用了2位,可用子网数=2的2次方=4个
作为一个B类地址,默认掩码是255.255.0.0 这里变成了255.255.255.0,可见从主机位借用了8位用来划分子网,一共划分了2的8次方 ...

传统的子网划分，网络地址要去掉头和尾，正如计算公式：子网数 = 2的N次方-2 ，这个没有问题。
因此，如果是C类地址划分/26子网，可用子网数应该是：2的2次方-2 = 2个。

QUESTION NO: 30
Your ISP assigned you a full class B address space. From this, you need at least 300
sub-networks that can support at least 50 hosts each. Which of the subnet masks
below are capable of satisfying your needs? (Select two).
你的ISP分配给你一个B类地址空间,你知道需要300个子网,每个子网至少需要50个主机,下面哪个掩码可以达到这个目的(2项)

A. 255.255.255.0
B. 255.255.255.128
C. 255.255.252.0
D. 255.255.255.224
E. 255.255.255.192
F. 255.255.248.0

解析:B类子网的默认掩码是255.255.0.0
每个子网如果需要50个主机,那么2的6次方(64)刚好大于50,留6个主机位便可.
需要300个子网,2的9次方刚好大于300,子网划分需要至少9比特
选项中满足这个条件的是B和E

答案:B,E

QUESTION NO: 31
A TestKing PC has the IP address 172.16.209.10 /22. What is the subnet of this address?
某主机地址为172.16.209.10 /22,请指出所在子网?

A. 172.16.42.0
B. 172.16.107.0
C. 172.16.208.0
D. 172.16.252.0
E. 172.16.254.0

解析:如果仅仅找出子网号,将IP地址和掩码做"与"运算便可
10101100.00010000.11010001.00001010
11111111.11111111.11111100.00000000
= 10101100.00010000.11010000.00000000

Answer: C

QUESTION NO: 32
You've been assigned the CIDR (classless inter domain routing) block of
115.64.4.0/22 from your ISP. Which of the IP addresses below can you use for a
host? (Select all valid answers)
你已经从ISP得到了CIDR类型的地址块115.64.4.0/22，下列哪个IP地址可以用在这个块中(多选)

A. 115.64.8.32
B. 115.64.7.64
C. 115.64.6.255
D. 115.64.3.255
E. 115.64.5.128
F. 115.64.12.128

解析：CIDR是将多个网段聚合后的结果，聚合时候匹配相同的最高位
因为前两个八位组相同，我们从第三个开始变成二进制
00000100 掩码11111100
看看每个选项
A.00001000...
B.00000111...
C.00000110...
D.00000011...
E.00000101...
F.00001100...
比较相同可以得出结论

答案：B,C,E

QUESTION NO: 33
A TestKing remote office branch is set up as shown in the diagram below:
All of the hosts in the above exhibit are connected with each other via the single
Catalyst switch. Which of the following statements correctly describe the addressing
scheme of this network? (Select three)
公司某个远程办公室的网络图如下



图中所有主机通过Catalyst同其他主机相连，关于本网络地址架构的表述中正确的是哪三条？

A. The subnet mask in use is 255.255.255.192.
B. The subnet mask in use is 255.255.255.128.
C. The IP address 172.16.1.25 can be assigned to hosts in VLAN1.
D. The IP address 172.16.1.205 can be assigned to hosts in VLAN1
E. The LAN interface of the router is configured with one IP address.
F. The LAN interface of the router is configured with multiple IP addresses.

解析：图中有两个VLAN
VLAN1 172.16.1.126 84个主机
VLAN2 172.16.1.129 114个主机
172.16.1.0网段默认子网掩码是255.255.0.0,既然分成子网，主机114台，应该留7个比特位够了，子网掩码是B
这两个子网是172.16.1.1-172.16.1.126和172.16.1.129-172.16.1.254
VLAN之间互联需要路由器，路由器应该有两个IP地址

答案：B, C, F

QUESTION NO: 34
The TestKing network is shown in the following diagram:
In the above network diagram, what are the broadcast addresses of the subnets?
(Select three)



看图说话：子网的广播地址是哪三个?

A. 172.16.82.255
B. 172.16.95.255
C. 172.16.64.255
D. 172.16.32.255
E. 172.16.47.255
F. 172.16.79.255

解析：图中有三个子网都是从172.16.0.0分出来，既然掩码是20位，可见划分了2的4次方＝16个子网
192.16.0.0
192.16.16.0
192.16.32.0
......
选项中：B是172.16.80.0的广播,E是172.16.32.0的广播,F是172.16.64.0的广播,

Answer: B, E, F

QUESTION NO: 35
Which one of the following varieties of NAT utilizes different ports to map multiple
IP addresses to a single globally registered IP address?
NAT的功能中那一个利用了映射多个IP地址到一个全球注册IP的特性?

A. Static NAT
B. Port loading
C. NAT Overloading
D. Dynamic NAT
E. None of the above

解析：静态NAT是一对一的关系，只有PAT才是多对一 PAT又叫NAT Overloading

答案：C