Check my subnetting?

The problem:
You have a IP of 202.99.212.0
You need 4 Subnets
I say Mask with 255.255.255.192
I say there will be 62 hosts per subnet
Nets are:
202.99.212.0
202.99.212.64
202.99.212.128
202.99.212.192
Am I correct?
formatting link
said I was wrong...and
they give the answer as:
Mask 255.255.255.224
With first host in the next net as 202.99.212.33
Which one of us is wrong? To me this says 8 subnets with 30 hosts per
subnet.
Brian
Reply to
Brian
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Brian, They are probably excluding all 0's and 1's, i.e. the first and last subnets. Lookup "subnet zero". This might help, see
formatting link
-- Ray
Reply to
Ray
Their quiz is for people who are studying MCSE-type exams as well as cisco. With Microsoft exams, all-zero and all-1 subnets are not counted. Look down the page, it says that they aren't for the purposes of this quiz.
By their rules, they are right and you are wrong. As with any exam, it's the exam answer that is correct ;-)
Reply to
John Petersen
Yes, indeed....
Question 113
What is your favorite color?
A - Blue B - Pink C - Red D- None of these E - All of these
According to the exam preparation study guides, your favorite color is skyblue-pink, so therefore D would be the correct answer.
Reply to
Brian
I did the same question-or one similar and came up with the same answer.
Reply to
daytime
I'd say you are correct IF you are using zero subnet command. The CCNA exam (allegedly) ignores this optional config command, therefore 224 is correct with 6 valid subnets - you have lost 2, plus are wasting 2, but that's the smallest mask to achieve 4.
PM
Reply to
Paul Morris
So ,when taking the CCNA ,one should not use the 1st and last subnet? I am hoping that they are more specific in their questions!
Reply to
daytime
Hi. Yes - I've been trying to dig it up in a couple of study books but no luck with a definitive quote yet. The rule of thumb I think (again I use the term allegedly) is that if the phrase 'zero subnet' is not present in the question then you have to disregard the first and last subnets. If it is, you must count them all.
ACL's are similar in that you can use that 'resequence' command from V12.4 onward, but that's not how the test treats it. As Brad Reese said in an earlier quote :"think in terms of doing it the 'Cisco Way'". Sagely advice.
PM
Reply to
Paul Morris
Many thanks-can you enlighten me on the resequence you mention for ACLs please? I am not aware of this-is it the implicit deny any at the end of the ACL? To digress slightly I am assuming hosts are classed as usable unless otherwise stated? for example .224 would be 30 usable 32 possible.
Reply to
daytime
CCNA may have questions that require use of subnet-zero (and all-1s subnet) and questions that do not. The hint is always meant to be there: they'll either say right out, or infer it by reference to e.g. using RIP as the routing protocol, VLSM or use of the words classful or classless in the question.
On the web-site the OP is using, it specifically says not to use subnet zero to answer the quiz - how specific do you want?
Like I said before, in an exam you are trying to see what answer the examiner is looking for, and the examiner is always right (even when they're wrong!).
Reply to
John Petersen
You are absolutely right Brian.
Reply to
Jeet
No, Brian was wrong in this case - there is no 'absolutely' about it: you need to learn to read questions thoroughly, or you will fail your CCNA.
Go look at the link he posted.
Reply to
John Petersen
Its not quite fair as it only tells you not to use subnet zero after you have answered the question-great link though-thanks alot.
Reply to
daytime
That link has taught me more about subnetting than anything else I have tried. I am very confident in my subnetting capabilities now.
Rule of thumb...if they say no zero nets and ask for subnetting to make 4, 8, 16, 32, 64, 128, 256 networks etc you better add two.
So if they want 4 nets, with no zero nets, then you need to figure for 6..so you need to borrow three bits for subnetting.
192.168.1.0/27 192.168.1.32/27 192.168.1.64/27 192.168.1.96/27 192.168.1.128/27 192.168.1.160/27 192.168.1.192/27 192.168.1.224/27
If the rule is no zero subnets, and you only use two borrowed bits you get:
192.168.1.0/26 192.168.1.64/26 192168.1.128/26 192.168.1.192/26
Which IS 4 subnets, but the first one doesn't count because this is a no zero subnet question.
SO...my lesson learned is to READ every word of the question twice, and don't assume a damn thing.
Reply to
Brian

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