From: vidhya natarajan (vidhyanatarajan@rediffmail.com)
Date: Sat Oct 08 2005 - 04:35:23 GMT-3
Thanks Victor... I was doing hex conversion thinking im doing decimal!!
On
Fri, 07 Oct 2005 Victor Cappuccio wrote :
>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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