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Instructions for using Windows Calc in decimal format for access list generation. posted 11/01/2003
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Ok, working off the binary math posted By Brian McGahan.

I've converted the method to work in decimal format on the windows calc.

The advantage here is that windows calc is useable in the lab!

This method has a simple sequence of operations, keeping down to
possibility of human error under stress. :)

Note - Logical operations work in any number base.

I've checked and it seems to work every time.

Also have had other people check it.


Instructions for using Windows Calc in decimal for accesslist

Operations are done per octet.  Processed in columns. 

Let`s do;;;

The Network value is defined as octets `AND`-ed together.

Example 55 & 33 & 36 =  32   ; Keep result. 

The Wildcard value is defined (in binary) as all ones = false, all
zeros=false anything else=true

But we will use the windows calc so you don`t have to worry about

Our next operation is to `Or` the same numbers.

55 | 33 | 36 = 55  ; Keep result

Now for the wildcard, take result of  `&` operation and result of  `|`
operation use the `XOR` operation on the two previous results.

32 xor 55 = 23

So the answer `` should match 55,33,36 

Checking with the boson wildcard util.  It checks.

In summary,

Using windows calc, in decimal numbers.

`AND` all the numbers of the octet column together.

Keep this result, this your network number for that octet.

`OR`  the same column, keep result.

`XOR` the two previous values, that`s the wildcard mask.

Simple Enough, and you can`t make binary mistake using method in the

Note - don`t discard zero results, it will be used later in method.


Please feel free to check method,

I believe it works in all cases.

Michael Snyder
Lead Network Engineer
Revolution Computer Systems
(270) 443-7400

-----Original Message-----
From: Cristian Henry H [mailto:chenry@xxxxxxxx] 
Sent: Tuesday, September 30, 2003 7:03 AM
To: Casey, Paul (6822)
Cc: ccielab@xxxxxxxxxxxxxx
Subject: Re: Access list filter in the shortest lines possible.

I got the following one:

access-list 10 permit

"Casey, Paul (6822)" ha escrito:
> > Hello,
> >
> > For example, say we are asked to filter the following routes using
> > shortest nuber of lines possible
> >
> >
> >
> >
> >
> >
> > Can someone tell me the best access list to use to filter these
> >
> > Thanks in advance.
> > Kind regards.
> >
> >
> >
> >