subnetting question - pissing me off

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For some reason, this question has me lost - particular cidr question

Which of the following IP addresses fall into the CIDR block of
110.68.4.0/18?


a) 110.68.8.32
b) 110.68.7.64
c) 110.67.6.255
d) 110.66.3.254
e) 110.65.5.128
f) 110.64.12.128


Book lists answers as B,C,E.


I see /18 meaning block size of size of 64.  I do know this is a class
A address being "110".


Some reason I am stumped on this one.  Any help appreciated.


subnetting question - pissing me off
For some reason, this question has me lost - particular cidr question

Which of the following IP addresses fall into the CIDR block of
110.68.4.0/18?


a) 110.68.8.32
b) 110.68.7.64
c) 110.67.6.255
d) 110.66.3.254
e) 110.65.5.128
f) 110.64.12.128


Book lists answers as B,C,E.


I see /18 meaning block size of size of 64.  I do know this is a class
A address being "110".


Some reason I am stumped on this one.  Any help appreciated.


subnetting question - pissing me off
For some reason, this question has me lost - particular cidr question

Which of the following IP addresses fall into the CIDR block of
110.68.4.0/18?


a) 110.68.8.32
b) 110.68.7.64
c) 110.67.6.255
d) 110.66.3.254
e) 110.65.5.128
f) 110.64.12.128


Book lists answers as B,C,E.


I see /18 meaning block size of size of 64.  I do know this is a class
A address being "110".


Some reason I am stumped on this one.  Any help appreciated.


Re: subnetting question - pissing me off
On 6 Oct 2006 rwest.eagle@gmail.com wrote:

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Work out what the range of ip addresses are covered by that block.
110.68.4.0/18 = 110.68.4.0 255.255.192.0.  Subtracting 192 in the
third octect from 256 gives you the block size of 64. So it will
covers 110.68.0.0 to 110.68.63.255 since 4 is in this range.  The
answer should have been all of them.

Doan



Re: subnetting question - pissing me off
The book gave the following answers:

Answers are: B, C, E.

A class A network address with a /18 is 255.255.192.0.

The subnets in the third octet are 0,64,128,192.  THE NETWORK ADdress
in the question is 110.64.0.0, with a bcast of 110.64.127.255, since
the next subnet is 110.64.128.0.



B,C,E are the correst host id's.


Can anyone work this out perhaps.




Doan wrote:
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Re: subnetting question - pissing me off
Errata for the book:


http://www.sybex.com/WileyCDA/SybexTitle/productCd-0782143911,navId-290611,pageCd-errata.html







It seems this book had updated errata Doan.  So the question is
technically wrong, it has no answer.

rwest.ea...@gmail.com wrote:
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Re: subnetting question - pissing me off

My mistake.  The third octet are being divided into blocks of 64. Thus,
256/64 = 4. So the subnets are: 0, 4, 8, 12, 16....252.  Since 110.68.4.0
falls into the second subnet, which covers 110.68.4.0 to 110.68.7.255.
Thus, the correct answers are B, C, E as the book said.

Doan

On 6 Oct 2006 rwest.eagle@gmail.com wrote:

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Re: subnetting question - pissing me off
Which of the following IP addresses fall into the CIDR block of
110.68.4.0/22? (Choose three.)
A. 110.68.8.32
B. 110.68.7.64
C. 110.68.6.255
D. 110.68.3.254
E. 110.68.5.128
F. 110.68.12.128
Answer: B, C, E.
New explanation:
A Class A network address with a /22 is 255.255.252.0. The subnets
in the third octet are 0, 4, 8, 12, etc. The network address in the
question is 110.68.4.0, with a broadcast of 110.68.7.255, since the
next subnet is 110.68.8.0. Answers B, C, and E are correct host IDs.











That's the updated question Doan.






Doan wrote:
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Re: subnetting question - pissing me off
Doan, notice the second Octets in the erratas updated question?


it's all .68's , meaning they fall  in the .64 subnet


original question is missprint with 2nd octets varrying, 68's, 67's,
66's, 65's, 64's



rwest.ea...@gmail.com wrote:
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Re: subnetting question - pissing me off
rwest.eagle@gmail.com wrote:

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The mask has changed too.
--
Paul Matthews                          
paul@cattytown.me.uk
http://www.hepcats.co.uk

Re: subnetting question - pissing me off
On 6 Oct 2006 10:37:06 -0700, rwest.eagle@gmail.com wrote:

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And this now works out after the mask change and ip corrections.

/bad editor!  bad!




Re: subnetting question - pissing me off
Yep, 5th edition of CCNA by sybex(Tod Lammel) is full of errors


This is not good, because this book is recommended to a lot of new
comers who dont want to spend the $$ on ccna wendel odom ciscopress
books



Im thinking about ditching my sybex book, because this is very
disconcerting when coming across errors like this.



Grog wrote:
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Re: subnetting question - pissing me off

rwest.eagle@gmail.com wrote:
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I used the book and thought it was pretty good, providing you corrected
the errors and downloaded the two extra chapters on OSPF elections and
NAT.

The question you quoted at the start had me stumped too for ages, until
I checked out the errata ;)


Re: subnetting question - pissing me off
rwest.eagle@gmail.com wrote:

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Paul's oft repeated tip. 256-mask = size of subnet.

18 - 255.255.192.0 so yup 64. But that network and mask don't look right.

That mask would give subnets of 110.68.0.0 and the next one would be
110.68.64.0.
--
Paul Matthews                          
paul@cattytown.me.uk
http://www.hepcats.co.uk

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