From: Scott Morris (swm@emanon.com)
Date: Tue Jul 11 2006 - 13:21:46 ART
Math logic makes my brain hurt sometimes...
In a wildcard mask:
1 bit - means there is change in the things you are looking at (e.g. don't
care whether 0 or 1 is used)
0 bit - means there is no change in this bit (e.g. stays the same as the set
point)
Keep it simple. You don't need windows calculator!
If you have 1,1,0 there are changes. A 1 goes in the mask. If you have
0,0,0 there are no changes and a 0 goes in the mask.
HTH,
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE
#153, CISSP, et al.
CCSI/JNCI-M/JNCI-J
smorris@ipexpert.com
http://www.ipexpert.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Shanky
Sent: Tuesday, July 11, 2006 4:47 AM
To: Prem Anand (hprem)
Cc: Leo Leung; ccielab@groupstudy.com
Subject: Re: IE Lab 20 11.2 Telnet Filtering
Hi,
According to the logic in the link below, for XOR Function with 3 inputs,
output will be 1 if one or all inputs are 1, so it will be 0 in case of even
no of 1s and in case all are 0 ?
http://www.dst-corp.com/James/LogicPrimer/Gates.html#Xor3
so XOR of 1,1,0 is 0 ...?
I thought XOR output will be 0, if all inputs are equal and 1 if any input
is different ..
so XOR output = 0, for 000,111 and 1 in all other cases.
Any comments?
On 7/11/06, Prem Anand (hprem) <hprem@cisco.com> wrote:
>
>
> (A & B & C) will have a bit set to 1 only when all 3 numbers have that
> bit set to 1 (A | B | C) will have a bit set to 0 only when all 3
> numbers have that bit set to 0
>
> So the XOR of the 3 numbers shud be (A & B & C) XOR (A | B | C)
>
> Any comments?
>
> Regards
> Prem
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of Shanky
> Sent: Tuesday, July 11, 2006 12:14 PM
> To: Leo Leung
> Cc: ccielab@groupstudy.com
> Subject: Re: IE Lab 20 11.2 Telnet Filtering
>
> Hi,
>
> Was wondering if anyone knows a way to use the windows calculator for
> AND
> , XOR functions for multiple entries ? I know it works for 2 entries
> but
> can we use it for more than 2
>
> Appreciate if anyone could help.
>
> Thanks
>
> Shanky
>
>
> On 7/11/06, Leo Leung <leoleung_yh@yahoo.com> wrote:
> >
> > Group,
> >
> > The question asks to have one line access-list for these 3 IP
> > addresses.
> >
> > Decimal Binary
> >
> > 45.194.169.115 00101101 11000010 10101001 01110011
> > 61.202.173.243 00111101 11001010 10101101 11110011
> > 41.234.41.250 00101001 11101010 00101001 11111010
> >
> > IP 41 194 41 114
> > Mask 20 40 132 137
> >
> > I came out with the following:
> >
> > ip access-list 1 permit 41.194.41.114 20.40.132.137
> >
> > but solution guide shows the access-list with 3 differences
> >
> > ip access-list 1 permit 41.194.41.112 20.60.134.137
> >
> > I am wondering if its typo or I miscalculated.
> >
> > Leo
> >
> >
> >
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