Check my subnetting?

Brian wrote:

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
http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080093f18.shtml

--
Ray

On Thu, 03 May 2007 22:37:43 GMT



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 ;-)

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.

I did the same question-or one similar and came up with the same
answer.

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

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!

On 5 May 2007 08:01:18 -0700



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!).

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

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.

You are   absolutely right Brian.

On 5 May 2007 21:20:41 -0700


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.

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.

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.