From: S Malik (ccie.09@gmail.com)
Date: Sat Sep 27 2008 - 09:13:00 ART
For Network portion it should be ANDed and for WC.Mask it should be XORed.
For AND operation all the bits should be 1 (high) and for XOR, if all the
bits are same (either all bits are 1 or 0) then o/p is 0,
Therefore AND will result in 0000 1000 = 8
XOR will result in 0000 0011= 3
On Fri, Sep 26, 2008 at 10:11 AM, Igor M. <imanassypov@rogers.com> wrote:
> 128.128.8.0
> 128.128.9.0
> 128.128.10.0
> 128.128.11.0
>
> You have too look for matching and differing octets, in this case octets
> 1,2
> and 4 are the same. Also you got to remember that '1' is a dont-care, and
> '0'
> is a 'match'
> Now the differing one - octet 3. Convert each one of them
> to binary:
>
> 0000 1000
> 0000 1001
> 0000 1010
> 0000 1011
> ---------
> 0000 1100 (bitwise AND) - this is your host portion of acl
> 0000 0011 (0 - match, 1 - dont care)
>
> ip access-list standard ACL-BB1
> permit 128.128.12.0 0.0.3.0
> hth
>
> ----------------------
>
> I.M., M.Eng. P.Eng.
>
> Network Architect
>
> CI Investments
>
> ----------------------
>
> --- On Fri, 9/26/08, Razzaq Shaikh <shaikh.razzaq@gmail.com> wrote:
> From: Razzaq Shaikh <shaikh.razzaq@gmail.com>
> Subject: Access-List ( Solution Explanation )
> To: "Cisco certification" <ccielab@groupstudy.com>
> Received: Friday, September 26, 2008, 9:50 AM
>
> Hello,
> Please someone can explain the solution
>
> queston) Allow only 128.128.8.0 / 128.128.9.0 /128.128.10.0
> /128.128.11.0routes from BB1
>
> answer) ip access-list standard ACL-BB1
> permit 128.128.8.0 0.0.3.255 ( * what is the formula for
> this )
>
>
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