CIDR question

[orv]

Perhaps I'm missing something but I've gone back a couple of times now to question 11 on the Chapter 3 review questions (p.152 5th Edition) and I'm not seeing how the answer is determined. I understand determing the subnet mask but I'm not seeing how 110.68.4.0/18 is a 110.64.0.0 network address with a 110.64.127.255 broadcast if the block size of 64 is in the 3rd octet. Could further explanation be given as to how the answers for correct host IDs is arrived at?

Thanks.

[muddyfox1009]

Same here, although i'm not using the 5thn ed.
With this Q, i got 0.0 and 63.255 using 64 blocksize. The 127.255 implies a blocksize of 128 (cidr 17).

I think the question is using 110.64.4.0 instead of 110.68.4.0 .

Can anyone correct me plz?

[dbeare]

Here is question 11 from the 5th edition book:

11. Which of the following IP addresses fall into the CIDR block of 110.68.4.0/22? (choose 3)

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

First off, lets find out how many networks and hosts can be in a /22 network:

/24 - 1 network, 255 hosts
/23 - 2 networks, 510 hosts
/22 - 4 networks, 1022 hosts

110.68.4.0/22 gives us an IP range of 110.68.4.0-110.68.7.255

This means that the valid IP's for this range are B, C and E.

Does that make more sense?

[muddyfox1009]

I worked this out differently with same results B, C and E. Here's how. the third octet have a block of 4. so for this particular Q, it need to start with 4.0 till 7.255 which is what B C and E are. Will this way work for every question of this nature?

Also your q11 of 5th ed. seems different from Orv's.

[dbeare]

Without knowing the entire question that he was asking, it is difficult to answer. I used the question from the 5th edition of the CCNA book for the old 640-801 exam. The 6th edition for the CCNA 640-802 is a different question entirely. Neither one sounds like his.

[D.bloge]

Who can post a question of the week? Does a question need permission/approval from Van or a mod??

[lammle]

Who can post a question of the week? Does a question need permission/approval from Van or a mod??

Knock yourself out. Let's see em'
Todd