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.

Reply to
rwest.eagle
Loading thread data ...

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.

Reply to
rwest.eagle

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.

Reply to
rwest.eagle

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

Reply to
Doan

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:

Reply to
rwest.eagle

Errata for the book:

formatting link

It seems this book had updated errata Doan. So the questi> The book gave the following answers:

Reply to
rwest.eagle

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

Reply to
Doan

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:

Reply to
rwest.eagle

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

snipped-for-privacy@gmail.com wrote:

Reply to
rwest.eagle

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.
Reply to
Paul Matthews

The mask has changed too.

Reply to
Paul Matthews

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

/bad editor! bad!

Reply to
Grog

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:

Reply to
rwest.eagle

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 ;)

Reply to
dilan.weerasinghe

Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.