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On Monday 31 July 2006 11:14, you wrote: > Brian, > > The math behind XOR is… > Given the inputs A1 and A2 the output Y is > Y = ( (NOT A1 AND A2) OR (A1 AND NOT A2) ) > > Such expression is only true if the inputs are different… > For three inputs… > > Y= ( ( NOT A1 AND NOT A2 AND A3 ) OR ( NOT A1 AND A2 AND NOT A3 ) OR > ( NOT A1 AND A2 AND A3 ) OR ( A1 AND NOT A2 AND NOT A3 ) OR ( A1 AND NOT A2 > AND A3 ) OR ( A1 AND A2 AND NOT A3 ) ) > > The expression is true only if the inputs are different… > That’s the beauty under XOR…. To be true only if the inouts are > different.. no matther the number of them… > My 0.02 > Ricardo > > On Saturday 29 July 2006 19:42, Brian wrote: > > Brian, > > > > Thank you for the clarification. > > > > —–Original Message—– > > From: Brian McGahan [mailto:bmcgahan@internetworkexpert.com] > > Sent: Saturday, July 29, 2006 3:35 PM > > To: Brian; Ricardo AF Silva > > Cc: ccielab@groupstudy.com > > Subject: RE: XOR for Computing ACL Masks > > > > You are correct, XOR does not hold true for an odd number of > > inputs. I believe the actual logic gate should be: > > > > AND(OR(A1,A2, …An),NOT(AND(A1,A2, …An))) > > > > Where A1 through An are the inputs. The result is that if all > > inputs are TRUE the result is FALSE, and if all inputs are FALSE the > > result is FALSE, regardless if there are an even or odd number of > > inputs. Any other combination results in TRUE. I’ll have to revise my > > document to make this a little clearer; for an odd number of inputs I > > don’t think there is a name for this gate. > > > > Thanks for the feedback, > > > > Brian McGahan, CCIE #8593 > > bmcgahan@internetworkexpert.com > > > > Internetwork Expert, Inc. > > http://www.InternetworkExpert.com > > Toll Free: 877-224-8987 x 705 > > Outside US: 775-826-4344 x 705 > > 24/7 Support: http://forum.internetworkexpert.com > > Live Chat: http://www.internetworkexpert.com/chat/ > > > > > —–Original Message—– > > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf > > > > Of > > > > > Brian > > > Sent: Friday, July 28, 2006 11:06 PM > > > To: ‘Ricardo AF Silva’ > > > Cc: ccielab@groupstudy.com > > > Subject: RE: XOR for Computing ACL Masks > > > > > > I agree with what you have stated and I understand. However this is > > > > not > > > > > an XOR. > > > > > > Brian > > > > > > —–Original Message—– > > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf > > > > Of > > > > > Ricardo AF Silva > > > Sent: Friday, July 28, 2006 10:53 AM > > > To: Brian > > > Cc: ccielab@groupstudy.com > > > Subject: Re: XOR for Computing ACL Masks > > > > > > Brian, > > > I think I got your point so, > > > > > > Given two inputs A & B, Xor’ed, the output Y is: > > > > > > A B Y > > > 0 0 0 > > > 0 1 1 > > > 1 0 1 > > > 1 1 0 > > > > > > For three inputs A, B and C, the output Y is: > > > > > > A B C Y > > > 0 0 0 0 > > > 0 0 1 1 > > > 0 1 0 1 > > > 0 1 1 1 > > > 1 0 0 1 > > > 1 0 1 1 > > > 1 1 0 1 > > > 1 1 1 0 > > > > > > Conclusion: > > > the inputs are different ( no matter how many inputs) Y is 1) > > > the inputs are the same, Y is 0… > > > That is the logic behind XOR… Look at the inputs and just check if > > > > are > > > > > equal > > > or not…. > > > > > > HTH > > > Ricardo > > > > > > As you can see in the example you have > > > > > > On Friday 28 July 2006 13:17, Brian wrote: > > > > I was using http://mathworld.wolfram.com/XOR.html as a reference. I > > > > > > am > > > > > > > interested in the specific process (steps) that were used in the > > > > example. > > > > > > > > Brian > > > > > > > > —–Original Message—– > > > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf > > > > > > Of > > > > > > > Mienbaikebi Patani > > > > Sent: Friday, July 28, 2006 9:00 AM > > > > To: Brian > > > > Cc: ccielab@groupstudy.com > > > > Subject: Re: XOR for Computing ACL Masks > > > > > > > > I think the XOR works such that u need to have equal number of 0 and > > > > 1 > > > > > > for > > > > the result to be equal to 1. Anything other than equal number of 0 > > > > and > > > > > 1 > > > > > > > results in a value equal to 0. > > > > > > > > Hope that was informative brother. > > > > > > > > On 7/28/06, Brian wrote: > > > > > I have been looking at the following example on how to calculate > > > > an > > > > > > > appropriate mask. > > > > > http://www.internetworkexpert.com/resources/01700370.htm. While I > > > > > understand the process that was use (and it works well) I cannot > > > > > > > > figure > > > > > > > > > out how the mask was calculated using XOR in example 2. If I > > > > > > > > understand > > > > > > > > > XOR correctly anytime there are an even number of 1’s in a > > > > > > computation > > > > > > > > the result of XOR will be 0. When there are an odd number of 1’s > > > > > > the > > > > > > > > result will be 1. This does not seem to hold true in the example. > > > > > > > > > > Can someone please help me understand how XOR was applied to come > > > > up > > > > > > > with the mask in example 2. Specifically the second octet is > > > > where > > > > > > the > > > > > > > > > confusion comes in. The only conclusions I can draw are that this > > > > > > is > > > > > > > > not truly an XOR or I do not understand XOR. > > > > > > > > > > By the way I tried to XOR 0011 in the MS calculator and the result > > > > > > is > > > > > > > 0. > > > > > > > > > Thanks! > > > > _______________________________________________________________________ > > > > > > > Subscription information may be found at: > > > > > http://www.groupstudy.com/list/CCIELab.html > > > > _______________________________________________________________________ > > > > > > Subscription information may be found at: > > > > http://www.groupstudy.com/list/CCIELab.html > > > > _______________________________________________________________________ > > > > > > Subscription information may be found at: > > > > http://www.groupstudy.com/list/CCIELab.html > > > > > > — > > > Eng Ricardo Ferreira > > > CREA 0601395632/D > > > > _______________________________________________________________________ > > > > > Subscription information may be found at: > > > http://www.groupstudy.com/list/CCIELab.html > > > > _______________________________________________________________________ > > > > > Subscription information may be found at: > > > http://www.groupstudy.com/list/CCIELab.html > > > > _______________________________________________________________________ > > Subscription information may be found at: > > http://www.groupstudy.com/list/CCIELab.html
– Eng Ricardo Ferreira CREA 0601395632/D