From: Victor Cappuccio (cvictor@protokolgroup.com)
Date: Fri Oct 07 2005 - 13:40:42 GMT-3
Hola Vidhya,
Ok Binary is for computers we are humans, so let the binary belong to
computers, we do the light part (Thinking)
This is a TIP:
Open Notepad
Open Windows Calc
Convert Dec -> Binary in the Windows Calc
Copy it
Paste it in notepad
So at the end you will have a list of 1 / 0 from all the IP Address,
lets take the one that Scott did
2 00000010
10 00001010
18 00010010
26 00011010
Now who to calculate de Mask, Use Logical ANDs and Logical XORs from
this list
/ Just in case you wonder XOR = 1 only if (0X1 | 1X0) and AND = 1 only
if (1A1)
Now,
AND would be 00000000
XOR would be 00011000
Copy those values to the windows calc (be sure to be in Bin mode), or
simple use this rule 128..64..32..16..8..4..2..1
Try that and you will find it very easy to do, because is math .-
HTH
Victor.
Leigh Harrison wrote:
> Vidhya,
>
> You're binary is bang on. bit 16 and bit 8 which = 24
>
> LH
>
> vidhya natarajan wrote:
>
>> Scott/Carl,
>>
>> Thanks for the reply.. I think the mask shud be .18?
>>
>> >2 00000010
>> >10 00001010
>> >18 00010010
>> >26 00011010
>> >Diff 00011000 = .24 Mask <---- would be a .18 mask isnt it?
>>
>> So the final one would be 200.0.1.2 0.0.2.18 ?
>>
>> Looking forward for your reply..
>>
>> Thanks,
>> Vidhya
>>
>>
>> On Thu, 06 Oct 2005 Carl Willias wrote :
>> >Scott you nailed it. I missed the third octet.
>> >
>> >CW
>> >
>> >----- Original Message ----
>> > From: Scott Morris <swm@emanon.com>
>> >To: Carl Willias <mandingo2073@yahoo.com>; Lee Donald
>> <Lee.Donald@t-systems.co.uk>; Leigh Harrison <ccileigh@gmail.com>;
>> ccielab@groupstudy.com
>> >Sent: Thursday, October 06, 2005 10:15:20 AM
>> >Subject: RE: Double Check access-list
>> >
>> >
>> >200.0.1.2
>> >200.0.3.2
>> >200.0.3.10
>> >200.0.1.18
>> >200.0.3.26
>> >200.0.1.10
>> >200.0.3.18
>> >200.0.1.26
>> >
>> >Third Octet:
>> >
>> >1 00000001
>> >3 00000011
>> >Diff 00000010 = .2 Mask
>> >
>> >Fourth Octet:
>> >
>> >2 00000010
>> >10 00001010
>> >18 00010010
>> >26 00011010
>> >Diff 00011000 = .24 Mask
>> >
>> >Remember that the router sees these things simply as strings of 32
>> bits.
>> >It's only our little brains that need the dotted-decimal octet
>> >representations. :)
>> >
>> >200.0.1.2 0.0.2.24 mask will give a total of three bits of
>> difference. 2^3
>> >yields 8 matches, and we have 8 lines listed.
>> >
>> >Scott
>> >
>> >
>> >-----Original Message-----
>> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
>> Behalf Of Carl
>> >Willias
>> >Sent: Thursday, October 06, 2005 11:02 AM
>> >To: Lee Donald; Leigh Harrison; ccielab@groupstudy.com
>> >Subject: Re: Double Check access-list
>> >
>> >I think the answer is
>> >
>> >200.0.3.2 0.0.0.24
>> >200.0.1.2 0.0.0.24
>> >
>> >CW
>> >
>> >----- Original Message ----
>> > From: Lee Donald <Lee.Donald@t-systems.co.uk>
>> >To: Leigh Harrison <ccileigh@gmail.com>; ccielab@groupstudy.com
>> >Sent: Thursday, October 06, 2005 9:05:05 AM
>> >Subject: RE: Double Check access-list
>> >
>> >
>> >Leigh,
>> >
>> >How's it going? Your access-list does work however it also includes
>> other
>> >hosts with your list that your not suppose to deny, for example
>> 200.0.2.16
>> >would also be denied using your list but the question does not ask
>> for that.
>> >
>> >Regards
>> >
>> >Lee.
>> >
>> >
>> >
>> >-----Original Message-----
>> > From: Leigh Harrison [mailto:ccileigh@gmail.com]
>> >Sent: 06 October 2005 14:49
>> >To: ccielab@groupstudy.com
>> >Subject: Double Check access-list
>> >
>> >Hey there,
>> >
>> >Could someone double check this for me? I think I've been staring
>> at the
>> >screen too long....
>> >
>> > From IEWB lab vol 1 17 Q.10
>> >
>> >Use the minumum lines necessary to deny these hosts:-
>> >
>> >200.0.1.2
>> >200.0.3.2
>> >200.0.3.10
>> >200.0.1.18
>> >200.0.3.26
>> >200.0.1.10
>> >200.0.3.18
>> >200.0.1.26
>> >
>> >I worked it out like this:-
>> >
>> >128 64 32 16 8 4 2 1 #
>> >0 0 0 0 0 0 0 1 1
>> >0 0 0 0 0 0 1 1 3
>> >
>> >0 0 0 0 0 0 1 0 2
>> >0 0 0 0 1 0 1 0 10
>> >0 0 0 1 0 0 1 0 18
>> >0 0 0 1 1 0 1 0 26
>> >
>> > From that, in the third octet, the only bit that cnages is 2 and both
>> >variables are present. In the fourth octet, the only bits that
>> change are
>> >the 16 and 8 bits and all 4 variables are present.
>> >
>> >So I came up with :-
>> >access-list 1 deny 200.0.1.2 0.0.2.24
>> >access-list 1 permit any
>> >
>> >However, the official answer is:-
>> >access-list 1 deny 200.0.1.2 0.0.2.8
>> >access-list 1 deny 200.0.1.18 0.0.2.0
>> >access-list 1 deny 200.0.1.26 0.0.2.0
>> >access-list 1 permit any
>> >
>> >Am I missing something ?!?
>> >
>> >Time for a brew.....
>> >LH
>> >
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>>
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