查看完整版本 : IP subnetting問睇,THX!!!

single63 2009-6-2 10:33 PM

IP subnetting問睇,THX!!!

[color=black][size=3][font=Times New Roman]Which of the following commands is correct to configure an interface to have the last usable host address in the subnet 192.168.64.32/29?[/font][/size][/color]
[color=black][font=Times New Roman][size=3] [/size][/font][/color]
[size=3][color=black][font=Wingdings][font=Wingdings]¡[/font][/font][/color][color=black][font=Times New Roman] A.
ip address 192.168.64.62 255.255.255.240[/font][/color][/size]
[size=3][color=black][font=Wingdings][font=Wingdings]¡[/font][/font][/color][color=black][font=Times New Roman] B.
ip address 192.168.64.62 255.255.255.248[/font][/color][/size]
[size=3][color=black][font=Wingdings][font=Wingdings]¡[/font][/font][/color][color=black][font=Times New Roman] C.
ip address 192.168.64.38 255.255.255.240[/font][/color][/size]
[size=3][color=black][font=Wingdings][font=Wingdings]¡[/font][/font][/color][color=black][font=Times New Roman] D.
ip address 192.168.64.38 255.255.255.248[/font][/color][/size]
[size=3][color=black][font=Times New Roman][/font][/color][/size]
[size=3][color=black][font=Times New Roman]點解答案係D訝,我只識計度255.255.255.248炸,192.168.64.38吳識計,PLS[/font][/color][/size]

mushroom1024 2009-6-3 12:42 AM

回覆 1# 的帖子

The subnet mask is 29, so the network bits on the last octal include
128,64,32,16,8.  Since the current subnet is 32, so the network bits must be

    128 64 32 16 8  4 2 1
     0    0    1  0  0


ie, the position for 4 2 and 1 make up the host bit.
and the largest value you can form for the host bit is
1 1 1 for the corresponding postion.  However, since the biggest value is
used as subnet broadcast, so the larget host can be 1 1 0

so, the when we put the subnet part and the host part together, we get

  0 0 1 0 0    1 1 0  in binary format
= 32 + 4 + 2 =38

lalala77 2009-6-3 01:47 AM

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ccl4 2009-6-3 01:52 PM

192.168.64.[color=Red][b][u]32[/u][/b][/color]/29

32 - 29 = 3 即係最後 3bit,由右手邊數起

X.X.X. xxxx x[color=Red]421[/color]
個 3 bit 既數值加埋係 7

一個 octet 全部 bit 著 1時加起來就係 255
將 255 - 7 = 248

所以 subnet mask 第四個 octet 係 255.255.255.248

29 bit 用於 subnetwork
3 bit 用於 host

192.168.64.[color=Red][b][u]32[/u][/b][/color]/29

    |xxx
  8|  9 - 14|15
16|17 - 22|23
24|25 - 30|31
[color=Red][b][u]32[/u][/b][/color]|33 - [color=RoyalBlue][b][u]38[/u][/b][/color]|39
40|41 - 46|47
48

32 號 subnetwork
usable host 由 33 ~ 38
1st : 192.168.64.33/29
2nd: 192.168.64.34/29
.
.
[color=RoyalBlue]last: 192.168.64.[b][u]38[/u][/b]/29[/color]
BC for 32號 subnetwork: 192.168.64.39/29

[[i] 本帖最後由 ccl4 於 2009-6-3 01:57 PM 編輯 [/i]]

single63 2009-6-4 09:46 AM

THX 各位大大,感激!

THX  各位大大,感激!
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