""s vermill"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Richard Burdette wrote: > > > > A prep test I am using has a question for which I disagree with > > the answer. Here is the question. > > > > If I had a Class B address, what subnet mask would I use if I > > wanted to split it into 8 class C addresses? > > > > > > a.255.255.240.0 > > b.255.255.255.0 > > c.255.255.248.0 > > d.255.255.254.0 > > > > The answer from the test is "c". > > > > I think the answer is not even listed; 255.255.224.0 because to > > add eight additional subnets we need 2^3=8 bits of subnet which > > equates to 224 of mask. Am I right or wrong? > > > > Rich > > > > > > The question sucks and so do the answer choices. Eight *addresses* per > subnet or eight subnets? If the former, a mask of 255.255.255.248 would be > required - not 255.255.248.0. If the latter, I'd go with you (sorta). Or > perhaps a. if subnet zero weren't allowed for some reason (but then you'd > have 15 subnets plus subnet zero - not eight!). > > Nothing you do with a subnet mask makes a class B a class C. If it was > class B before you subnetted it, it isn't going to fall into the class C > range of addresses all of the sudden is it? If by "class C" they mean a > subnet with 254 host addresses, your answer isn't right either. Your > subnets (/21) would have 8190 hosts. In that case, there isn't a valid > answer at all because a class B subnetted for 254 hosts will have somewhere > in the neighborhood of 255 subnets.
CL: I disagree. 172.16.0.0/21 gives you eight subnets, each with a mask of /24 - subnets 172.16.0.0/24 through 172.16.7.0/24, for example. Think ISP / BGP :-) > > I would be wary of the "practice" test as a whole. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=58582&t=58569 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
