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 ;-)
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.
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.
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.
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!).