""B.J. Wilson"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > You sure about that, Chuck? ;-)
CL: well..... yeah I understand the subnet zero argument. It's been too long since I studied anything from a CCNA level. CL: to be truthful, I have never bothered with the 2n-2 issue in real world or in my CCIE studies. ip subnet-zero renders that irrelevant. CL: If I don't pass my lab next time, I am facing a CCNP/DP recert, so I guess I should keep that in mind ;-> > > 2^n-2 = 8 ! a total of 8 subnets needed ! > 2^n = 10 ! add 2 to both sides ! > n = 4 ! 2^4-2 = 14 ! > > 128 64 32 16 8 4 2 1 > 1 1 1 1 0 0 0 0 > > = 240, or answer A in the original post. > > BJ > > > > -------Original Message------- > From: The Long and Winding Road > Sent: 12/05/02 09:48 AM > To: [EMAIL PROTECTED] > Subject: Re: VLSM Question [7:58569] > > > you sure about that, Tom? > > > 172.100.00000000.0 > 255.255.11100000.0 > subnet bits = 11111.0 > 172.100.0.0 through 172.100.31.0 for /24's > > these would be SUMMARIZED using the 224 mask in the third octet. > > if you only want eight /24's, then the answer is > > 172.100.00000000.0 > 255.255.11111000.0 > subnet bits = 111 eight subnets of /24 > summarized as 172.100.0.0/21 ( 248 ) > > > > -- > TANSTAAFL > "there ain't no such thing as a free lunch" > > > > > ""Tom Lisa"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > If the test prep you are using is for the CCNA exam then "C" is the > > correct > > "Cisco" answer (the use of Class B/Class C terminology makes me think > > this is the case). This is because Cisco still insists, at the CCNA > > level, on > > computing subnets using the formula 2^n-2. This assumes that subnet > > zero and the all ones subnet are unusable. Therefore you have to create > > 16 subnets, resulting in 14 "usable" to get the required 8 subnets. > > > > In the "real" world, 255.255.224.0 is correct. > > BTW, what is the VLSM question here? > > > > HTH, > > Prof. Tom Lisa, CCAI > > Community College of Southern Nevada > > Cisco ATC/Regional Networking Academy > > "Cunctando restituit rem" > > > > 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 > > > > > > > > > > [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=58626&t=58569 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
