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IP adreses calc from subnet mask

Posted on 2009-03-30
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Last Modified: 2013-11-23
How to write procedure where I can from example 192.168.0.0/24 get all IP adress 192.168.0.1- 192.168.0.255 into stringlist. where is mask is 24 there is simple but how to make where ip with mask is 213.21.192.0/18 or 192.168.0.30/28
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Question by:KarlisB
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by:KarlisB
Comment Utility
Maybe someone can give procedure to make like :
http://www.aboutmyip.com/AboutMyXApp/SubnetCalculator.jsp?ipAddress=192.168.0.0&cidr=20

and calculate first IP address and last IP address
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by:ahalya
Comment Utility
I am not conversant in IP traffic, but it appears the number after the slash shows you the number of bit to turn on in the mask.

16 -> Mask: 255.255.0.0
17-> Mask: 255.255.128.0

I'll try to implement an algorithm to give you a list. (Correct me if my interpretation is wrong).

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ahalya earned 500 total points
Comment Utility
Here is the code to list the IP in tha range given the IP & the mask bits.  I have simply used logical operands to expand the list.

Call the 'GetIPList' function with two arguments: IP-v4 address, and the MaskBits.

e.g., GetIPList('192.168.0.0', 22);


type TIPSegments = array[1..4] of byte;
 

function NumberToSegments(Number:longword):TIPSegments;
 

var j : 0..4;
 

begin;

  for j := 4 downto 1 do

  begin;

    result[j] := Number mod 256;

    Number := Number div 256;

  end;

end;
 

function IPToSegments(ip:string):TIPSegments;
 

var i : byte;

    j : 0..4;

    s : string;
 

begin;

  for j := 1 to 4 do

  begin;

    i := pos('.', ip);

    if j < 4 then s := copy(ip, 1, i-1) else s := ip;

    delete(ip, 1, i); //remove '.'

    result[j] := StrToInt(s);

  end;

end;
 
 

function IPToNumber(ip:string):longword;
 

var segment : TIPSegments;

    i : 1..4;
 

begin;

  segment := IPToSegments(ip);

  result := 0;

  for i := 1 to 4 do

    result := result * 256 + segment[i];

end;
 

function NumberToIP(Number:longword):string;
 

var segment : TIPSegments;

    i : 1..4;
 

begin;

  result := '';

  segment := NumberToSegments(Number);

  result := Format('%d.%d.%d.%d', [segment[1], segment[2], segment[3], segment[4]]);

end;
 
 

procedure TForm4.GetIPList(IPStr:string; MaskBits:byte);
 

var

  IP   :LongWord;

  i, w : longword;
 

begin;

  IP := IPToNumber(IPStr);
 

  WildCard := 1 shl (32 - MaskBits) - 1;

  NetMask := not WildCard;
 

  leWildCard.text := NumberToIP(WildCard);

  leNetMask.text  := NumberToIP(NetMask);
 

  ListBox1.Items.Clear;

  for w := 1 to WildCard - 1 do

  begin;

    i := IP or w;

    ListBox1.Items.Add(NumberToIP(i));

  end;

  leCount.text    := IntToStr(ListBox1.Items.Count);

end;

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Expert Comment

by:ahalya
Comment Utility
by the way, it appears that you'd need a Stringlist with duplicates set to dupIgnore, instead of a ListBox to make this work for any generic IP address.

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Author Comment

by:KarlisB
Comment Utility
please give what type of variables is:

Wildcard
NetMask
IeWildcard

bacause I have:

[Error] Unit2.pas(106): Undeclared identifier: 'WildCard'
[Error] Unit2.pas(107): Undeclared identifier: 'NetMask'
[Error] Unit2.pas(109): Undeclared identifier: 'leWildCard'
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Expert Comment

by:ahalya
Comment Utility
Type for WildCard and NetMask is LongWord.  Anything where name starts with le* is just a TEdit which I used to display the calculated value.

Just to give a quick comment about what I am doing:

1. Convert the IP address in to an integer (There are four 'segments' each going from 0 to 255, i.e. 8 bits. so you need a total of 32 bits hence the LongWord  -for IP-v4)

2. WildCard is an integer correspoding to the Mask.

3. NetMask is the (binary) inverse of the WildCard which has to be 'Logical-OR'ed with the original IP to get the list.



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Expert Comment

by:ahalya
Comment Utility
My wording isn't clear above:

2.  WildCard corresponds to the number of bits in the Mask, and that is the one you have to "Logical-OR' with the IP to get the list.

3.  NetMask is the binary inverse of WildCard, and gives you the 'SubNet Mask' in the traditional form (e.g. 255.255.255.0).
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