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Home > Archive > CCNA > April 2004 > Subnetting question
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Subnetting question
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| repentantvoter 2004-04-26, 1:40 pm |
| Got this question...
Class C network is subnetted with mask 255.255.255.240. How many subnets and how many hosts per subnet do you get?
1. 16 subnets and 16 hosts per subnet
2. 14 subnets and 14 hosts per subnet
3. 16 subnets and 14 hosts per subnet
4. 14 subnets and 16 hosts per subnet
My answer was 3, but was told right answer is 2. How come?? 
TIA | |
| forbesl 2004-04-26, 1:54 pm |
| In the REAL world, you are correct; however, in the Cisco training/test world, #2 is correct. I don't know why Cisco doesn't change their training methods and tests to reflect how things really are. Here's a link to why maybe Cisco feels this way:
http://www.cisco.com/en/US/tech/tk648/tk361/ technologies_tech_note09186a00
80093f18.shtml | |
| repentantvoter 2004-04-26, 2:03 pm |
| quote:
Originally posted by forbesl
In the REAL world, you are correct; however, in the Cisco training/test world, #2 is correct. I don't know why Cisco doesn't change their training methods and tests to reflect how things really are. Here's a link to why maybe Cisco feels this way:
http://www.cisco.com/en/US/tech/tk6...
80093f18.shtml
Thanks for the very interesting link, Mr. forbesl. I have added it to my Favorites. 
I think you are right about Cisco's training methods. I thought CCNA is meant to prepare people for the real world. What gives?? | |
| ASnowy 2004-04-28, 12:35 pm |
| Uuupps... what a very good question and not minus great answer!
I know about the problematic use of all-zeros and all-ones subnets, nonetheless valid subnets.
Now, i became confuse about choosing a correct answer for similar questions.
My doubt... 
depending on Microsoft or Cisco exams,the correct answer to this question would be 3 or 2 respectively ??
In other way, the adverted document at cisco's URL finally say (complaining about the potential problems and making reference to rfc 1878) that this practice of excluding this subnets is obsol
ete .
For that reason, the only one valid and very correct response will be 3 . | |
| forbesl 2004-04-28, 1:07 pm |
| quote:
Originally posted by ASnowy
In other way, the adverted document at cisco's URL finally say (complaining about the potential problems and making reference to rfc 1878) that this practice of excluding this subnets is obsol
ete .
Agreed, that practice is obsolete and answer "3" is correct, but try answering "3" on a Cisco test and see if you get it right. | |
| Goldorak 2004-04-28, 5:54 pm |
| Correct me if i am wrong. But, does wheather you can use all 0s and all 1s not depend on the version of ois you are running? And if so, surely that should be stipulated in the question. | |
| forbesl 2004-04-28, 6:22 pm |
| quote:
Correct me if i am wrong. But, does wheather you can use all 0s and all 1s not depend on the version of ois you are running? And if so, surely that should be stipulated in the question.
You can use subnet zero and the all 1's subnet on any Cisco IOS; however,
for Cisco IOS versions prior to 12.0 you must configure "ip subnet-zero" in global config mode if you want to use subnet zero. For versions 12.0 and above ip subnet-zero is on by default. And no, that is not stipulated if you have a question like that for the exam. |
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