From: RIDNEY_M_LAUDIANO.TTSP@ts.tsuneishi.co.jp
Date: Fri Dec 23 2005 - 00:51:01 GMT-3
i would like to add that we can use the windows calculator to do the *And* and
*Xor* calculation (saving cpu process) ;)
10.20.30.40
40.30.20.10
permit using one-line filter
10 And 40: 8 (subnet)
10 Xor 40: 34 (mask)
..
...
....
access-list 101 permit 8.20.20.8 34.10.10.34
regards,
ridney
"Scott Morris" <swm@emanon.com> wrote on 12/23/2005 10:52:36 AM:
) [image removed]
) So you're saying the mask would be 8.20.20.8???
) First, that's mathematically incorrect but we'll worry about that in a
) moment.
) Second, look at the mask in binary:
) 00001000.00010100.00010100.00001000... There are 6 one-bits in there. 2^6
) = 64 matches to that mask alone. You only listed two things to match.
) If you are FORCED to come up with a one-line ACL that may be acceptable,
) otherwise I would advise against it. If you don't care how many extra
) things you're permitting or denying just use "any any" to save the brain
) power.
) So on the math side, I think you're looking at it wrong for what bits go
) where. If your two values have a bit in common you do NOT put a one-bit in
) the mask. The XOR would be 0. So your 8-bit-position value, since they
) both have it would yeild a 0 in that position whereas the 32 and 4 bit
) positions would have a 1 in the mask.
) So to get them in one line:
) 00100010.00001010.00001010.00100010 which is worse because it gives 8 bits
) of 1's in the mask and 2^8 = 256 matches.
) 34.10.10.34 would be your mask if your were FORCED to come up with a
) one-line ACL. IMHO this is rare and not incredibly bright. If your lab
) tells you to do it, well... Just do it. ;)
) Scott
) -----Original Message-----
) From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
) Venkatesh Palani
) Sent: Thursday, December 22, 2005 9:28 PM
) To: Scott Morris
) Cc: Farrukh Haroon; Khurana, Sameer; Emil Patel; Nawaz, Ajaz; nenad pudar;
) bmcgahan@internetworkexpert.com; ccielab@groupstudy.com
) Subject: Re: Question for Brian McGahan and others
) sorry I just realized there is a TYPO
)
) vlaue for 30 is 16+8+4+2 and not 16+4+2.
)
) ThanX
)
) On 12/23/05, Venkatesh Palani <kvpalani@gmail.com> wrote:
) >
) >
) > Hi All,
) >
) > Thanks Scott, I personllay dont use binary rather I use Decimal.
) >
) > below is the technique
) >
) > for instance lets take the same example from IE
) >
) > 10.20.30.40
) > 40.30.20.10
) >
) > to find a access list for these address with overlapping networks I
) > wld write the aboves address as shown below
) >
) > [8+2].[16+4].[16+4+2].[32+8]
) > [32+8].[16+4+2].[16+4].[8+2]
) >
) > and the common vlaues in two colums shld represent the network
) > address and the remaining shld fall back as wild cad mask
) >
) >
) > in this case it will be
) >
) > 8.[16+4].[16+4].[8] = 8.20.20.8
) >
) > and the wild card mask is the sum of the left overs(the vlaues that
) > were not used in the network address) in each octects from all the
) > rows(in this case only two rows)
) >
) > [32+2].[8+2].[8+2].[32+2] = 34.10.10.34
) >
) >
) > This shld work for any no of rows , this works better for me rather
) > than those AND and XOR operations. Any comments are welcome.
) >
) >
) > Thanx,
) >
) > Venkatesh
) >
) >
) > On 12/23/05, Scott Morris <swm@emanon.com> wrote:
) > >
) > > From: http://en.wikipedia.org/wiki/Xor
) > >
) > > The case of a three, or more, input XOR operation tends to be an
) > > ill-considered case. An XOR operation with three simultaneous inputs
) > > is not so easily expressed in most popular programming languages.
) > > When expressed as successive binary operations the result is a
) > > simple parity, giving a TRUE result for any odd number of TRUE
) > > inputs.
) > > three ones XORed simultaneously
) > >
) > > When taken as a multi-input black box whose operation follows the
) > > formal
) > >
) > > definition and yields the result TRUE when one, and only one, of its
) > > inputs is TRUE, the behaviour is inconsistent with the successive
) > > binary mode.
) > > For
) > > example; in the case where three inputs are all TRUE (as shown on
) > > the right, in the IEC symbology to emphasise the definition) the
) > > result would have to be FALSE because it does not meet the condition
) > > that "only one of its inputs is TRUE".
) > > [edit]
) > >
) > >
) > > -----Original Message-----
) > > From: nobody@groupstudy.com [mailto: nobody@groupstudy.com] On
) > > Behalf Of Farrukh Haroon
) > > Sent: Thursday, December 22, 2005 3:54 PM
) > > To: Khurana, Sameer
) > > Cc: Emil Patel; Nawaz, Ajaz; nenad pudar;
) > > bmcgahan@internetworkexpert.com; ccielab@groupstudy.com
) > > Subject: Re: Question for Brian McGahan and others
) > >
) > > what happened to the definition of XOR I learnt in college....
) > >
) > > Odd Number of 1's in input Results in Output of 1, Output = 0
) > > otherwise...
) > >
) > > ??
) > >
) > > On 12/22/05, Khurana, Sameer < SKHURANA@amfam.com> wrote:
) > > >
) > > > I think you meant by column ;)
) > > >
) > > > Concept remains the same if its 4 rows, 5 rows or 10 rows.
) > > >
) > > > -----Original Message-----
) > > > From: nobody@groupstudy.com [mailto: nobody@groupstudy.com] On
) > > > Behalf Of Emil Patel
) > > > Sent: Thursday, December 22, 2005 11:37 AM
) > > > To: 'Nawaz, Ajaz'; 'nenad pudar'; bmcgahan@internetworkexpert.com
) > > > ; ccielab@groupstudy.com
) > > > Subject: RE: Question for Brian McGahan and others
) > > >
) > > >
) > > > If the row is dissimilar the end result is 1.
) > > >
) > > >
) > > > -----Original Message-----
) > > > From: nobody@groupstudy.com [mailto: nobody@groupstudy.com] On
) > > > Behalf Of Nawaz, Ajaz
) > > > Sent: Thursday, December 22, 2005 11:05 AM
) > > > To: 'Emil Patel'; 'nenad pudar'; bmcgahan@internetworkexpert.com;
) > > > ccielab@groupstudy.com
) > > > Subject: RE: Question for Brian McGahan and others
) > > >
) > > > What happens when you increase the #vertical rows and apply
) > > > various combinations of 1's and 0's.
) > > >
) > > > Let's try 5rows?
) > > >
) > > > Tia
) > > > Ajaz Nawaz
) > > >
) > > >
) > > > -----Original Message-----
) > > > From: nobody@groupstudy.com [mailto: nobody@groupstudy.com ] On
) > > > Behalf Of Emil Patel
) > > > Sent: 22 December 2005 17:07
) > > > To: 'nenad pudar'; bmcgahan@internetworkexpert.com;
) > > > ccielab@groupstudy.com
) > > > Subject: RE: Question for Brian McGahan and others
) > > >
) > > > In XOR , if bit in a column is dissimilar result is 1. You do not
) > > > add bit row by row.
) > > >
) > > > -----Original Message-----
) > > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
) > > > Behalf Of Emil Patel
) > > > Sent: Thursday, December 22, 2005 10:49 AM
) > > > To: 'nenad pudar'; bmcgahan@internetworkexpert.com;
) > > > ccielab@groupstudy.com
) > > > Subject: RE: Question for Brian McGahan and others
) > > >
) > > > 128 64 32 16 8 4 2 1
) > > >
) > > > 0 0 0 0 0 0 0 0
) > > > 0 0 0 0 0 1 0 0
) > > > 0 0 1 0 0 0 0 0
) > > > 0 0 1 0 0 1 0 0
) > > > ___________________________________________
) > > > 0 0 1 0 0 1 0 0 = 36
) > > >
) > > > All vertical bits are checked XOR and if they are:
) > > > (0+0)=0
) > > > (0+1)=1
) > > > (1+1)=0
) > > > (1+0)=1
) > > >
) > > >
) > > > -----Original Message-----
) > > > From: nobody@groupstudy.com [mailto: nobody@groupstudy.com] On
) > > > Behalf Of nenad pudar
) > > > Sent: Wednesday, December 21, 2005 7:57 PM
) > > > To: bmcgahan@internetworkexpert.com; ccielab@groupstudy.com
) > > > Subject: Question for Brian McGahan and others
) > > >
) > > > Hi Brian
) > > > I have the question regarding your paper on Computing Access-List
) > > > and Wildcard Pairs
) > > >
) > > > There you have
) > > >
) > > > 00000000
) > > > 00000100
) > > > 00100000
) > > > 00100100
) > > > _________
) > > > XOR
) > > > 00100100=36****
) > > >
) > > > I cannot get this trying in any way (for third column)
) > > >
) > > > 1) (((0 XOR 0) XOR 1) XOR 1)= ((0 XOR 1) XOR 1)= 1 XOR 1 =0
) > > >
) > > > 2) (0 XOR 0) XOR (1 XOR 1) = 0 XOR 0 = 0
) > > >
) > > > I am doing something wrong or there is some other trick here ?
) > > >
) > > >
) > > > thanks
) > > > nenad
) > > >
) > > > __________________________________________________________________
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