From: Chris Larson (clarson52@xxxxxxxxxxx)
Date: Sun Apr 28 2002 - 22:02:09 GMT-3
I guess this did not come out right so you can't really follow it. Sorry.
----- Original Message -----
From: "Chris Larson" <clarson52@comcast.net>
To: "Babacar Diop" <babacard2000@yahoo.com>; <fningham@att.net>
Cc: "cciegroup" <ccielab@groupstudy.com>
Sent: Sunday, April 28, 2002 6:26 PM
Subject: Re: Conversion canonical to non-canonical
> If it is ethernet, and you are building filters for dlsw always convert.
>
>
> As for converting, you do not need to memorize the numbers if you convert
to
> binary flip then swap.
> I only know 1 way to convert and it is probably the same as everyone else
> except I find it eaiser to flip the binary reference then trying to flip
the
> binary number. It just seems to be quicker and I can do it without
thinking
> too much. A hex number is represented by a nibble or half a byte in
binary.
> Take 2 hex digits at a time, convert them to binary, flip the binary
number
> (or reference ) and reverse their places.
>
> Canonical: = 04 5a 49 88 d7
>
> Take the first 2 numbers and convert to binary
>
> binary reference 8421
> 8421
> 0 in binary = 0000 4 in binary =
0100
>
> Now we have the binary number we flip it. I find it easier to flip the
> reference rather then flipping the binary number. The way I was taught of
> course was to flip the binary number (not the reference as shown), but
this
> seems to be a waste of time, and for me is a little more difficult to do
in
> my head then just reversing the reference. Just count the reference
> backwards.
>
> 1248 1248
> 0 flipped = 0000 4 flipped = 0100 or 2
>
> of course zero is zero in hex and 4 is 2 in hex. All we have to do is
swap
> places from the two numbers we took. Just swap the first and second
numbers
> so the non canonical equivelant of this excerise is
>
> 20
>
> moving to the next group of two hex numbers. 5A
>
> 8421 8421
> 1248 1248
> 5 = 0101 a= 1010 flip 'em
> 0101 = a hex 1010 = 5 hex
>
> swap places 5a we now have 205a.
>
> 8421 8421 1248
> 1248
> 4 = 0100 9 = 1001 flip 0100 =2
> 1001 = 9. swap 92 now we have 205a92. 8 is relatively easy
> especially since there are 2 in a row. 8 flipped of course is 1. so 11. we
> have 205a9211, and lastly
>
> 8421 8421
1248
> 1248
> d= 1101 7 = 0111 flip 1101 =b
> 0111 = e swap eb
>
> 205a9211eb
>
>
>
>
>
> ----- Original Message -----
> From: "Babacar Diop" <babacard2000@yahoo.com>
> To: <fningham@att.net>
> Cc: "cciegroup" <ccielab@groupstudy.com>
> Sent: Sunday, April 28, 2002 3:56 PM
> Subject: Re: Conversion canonical to non-canonical
>
>
> > Does anyone has a better explanation for this? I would
> > really appreciate it. Also, is there an easy way to do
> > the conversion or does one have to memorize how to
> > convert every single digit/character?
> >
> > Thanks
> >
> >
> > --- fningham@att.net wrote:
> > > DLSW uses only non-canonical addresses so you would
> > > need to convert whenever you have an Ethernet
> > > address
> > > to use in a DLSW statement. This could be in a
> > > icanreach statement, or in a MAC filter access-list.
> > >
> > > HTH, Fred
> > > > Group,
> > > >
> > > > When do you need to convert from canonical to
> > > > non-canonical in DLSw. Anyone as a doc on when and
> > > how
> > > > to do it?
> > > >
> > > > Thanks
> > > >
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