| Author |
Which answer is correct
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| sukuvi 2002-06-25, 2:33 am |
| Hi everyone,
Please try this summarization exercise and tell me which answer is correct.
The networks 202.16.0.0, 202.16.1.0, 202.16.2.0, and 202.16.3.0 can be summarized by using which of the following?
A. 202.16.0.0/24
B. 202.16.4.0/23
C. 202.16.0.0/23
D. 202.16.0.0/22
I found the answer is 202.16.0.0/21 but it is not even listed. The book says it is 202.16.0.0/22. But I think that answer would be correct only if the network 202.16.3.0 is not included in the summarization. | |
| Yankee 2002-06-25, 3:13 am |
| A /21 network would be a 255.255.248.0 mask and would effectively give you 8 class C blocks - 202.16.0.0 thru the 202.16.7.255.
A /22 network would give you 4 class Cs and a 255.255.252.0 mask - 202.16.0.0 thru 202.16.3.255 block so it is the right answer.
Yankee | |
| Wallis Short 2002-06-25, 3:26 am |
| Hi Sukuvi
The correct answer is 202.16.0.0/22.
If we take the first and last ip addresses (shortcut) and write them out in binary we see we get this
11001010 00010000 00000000 00000000
11001010 00010000 00000011 00000000
We see that until we get to the 3rd octec all the 1'a and 0's are the same.
Therfore we count the bits from the left hand side and we get 22 - Thats the subnet mask of 255.255.252.0
To work out the summarised network we look at the 1's up to where they are different in the 3rd octet and we see we get
11001010 00010000 000000.. ........
202 16 0 0
Therefore the network summary is
202.16.0.0 /22
Hope this helps
Cheers
Wallis  | |
| sukuvi 2002-06-25, 6:24 am |
| Thanks Wallis Short and Yankee.
I just realized I screwed up while converting 202.16.3.0 to binary. I got
11001010 00010000 00000101 00000000
instead of
11001010 00010000 00000011 00000000
and that's what made me conclude the book answer was wrong.
I should have noticed that mistake immediately because 3 in binary is 11 and not 101.
Anyway I learned the lesson: I need to be VERY VERY careful when doing these conversions mentally because the least mistake and it's all wrong. |
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