PHP Forum

**simptech** · 03-23-2005, 11:09 AM

Let's say i want to check against 69.189.55.128/25

Of course the low range would be 69.189.55.128 and I am pretty sure the high range is 69.189.55.255

Currently I am using the following code:

Code:

function ip_allowed() {
  $lo = ip2long("69.189.55.128");
  $hi = ip2long("69.189.55.255");
  $ip = ip2long($_SERVER['REMOTE_ADDR']);
  return ($ip >= $lo && $ip <= $hi);
}
 
/* Check for valid IP address */
if (!ip_allowed()) exit("Access denied!");

I would like to use something more dynamic like:

Code:

function ip_allowed($val) {
  list($ip_lo, $ip_mask) = split("/", $val);
  $ip_lo = ip2long($ip_lo);
  $ip_hi = ip2long(CALCULATED_VALUE_FROM_IP_MASK);
  $ip_user = ip2long($_SERVER['REMOTE_ADDR']);
  return ($ip_user >= $ip_lo && $ip_user <= $ip_hi);
}
 
/* Check for valid IP address */
if (!ip_allowed("69.189.55.128/25")) exit("Access denied!");

Does anybody know how to determine the maximum range by performing calculations on the ip mask?

**0beron** · 03-23-2005, 06:47 PM

If you have a mask of 25, you can get the equivalent long value by left shifting a hex value of all ones. For a mask of /25 you want to shift by 7:

PHP Code:


			
<?php





function calculate_mask($range) {

  $shift = 32 - $range;

  $mask = 0xffffffff << $shift;

  printf("Range: \\$range<br />Binary Mask:\t%b<br />",$mask);

  printf("Dotted quad mask:\t%s<br /><br />",long2ip($mask));

}



for($i=10; $i<28; $i++) {

  calculate_mask($i);

}



?>

gets you:

Code:

Range: \10
Binary Mask: 11111111110000000000000000000000
Dotted quad mask: 255.192.0.0

Range: \11
Binary Mask: 11111111111000000000000000000000
Dotted quad mask: 255.224.0.0

Range: \12
Binary Mask: 11111111111100000000000000000000
Dotted quad mask: 255.240.0.0

Range: \13
Binary Mask: 11111111111110000000000000000000
Dotted quad mask: 255.248.0.0

Range: \14
Binary Mask: 11111111111111000000000000000000
Dotted quad mask: 255.252.0.0

Range: \15
Binary Mask: 11111111111111100000000000000000
Dotted quad mask: 255.254.0.0

Range: \16
Binary Mask: 11111111111111110000000000000000
Dotted quad mask: 255.255.0.0

Range: \17
Binary Mask: 11111111111111111000000000000000
Dotted quad mask: 255.255.128.0

Range: \18
Binary Mask: 11111111111111111100000000000000
Dotted quad mask: 255.255.192.0

Range: \19
Binary Mask: 11111111111111111110000000000000
Dotted quad mask: 255.255.224.0

Range: \20
Binary Mask: 11111111111111111111000000000000
Dotted quad mask: 255.255.240.0

Range: \21
Binary Mask: 11111111111111111111100000000000
Dotted quad mask: 255.255.248.0

Range: \22
Binary Mask: 11111111111111111111110000000000
Dotted quad mask: 255.255.252.0

Range: \23
Binary Mask: 11111111111111111111111000000000
Dotted quad mask: 255.255.254.0

Range: \24
Binary Mask: 11111111111111111111111100000000
Dotted quad mask: 255.255.255.0

Range: \25
Binary Mask: 11111111111111111111111110000000
Dotted quad mask: 255.255.255.128

Range: \26
Binary Mask: 11111111111111111111111111000000
Dotted quad mask: 255.255.255.192

Range: \27
Binary Mask: 11111111111111111111111111100000
Dotted quad mask: 255.255.255.224

**simptech** · 08:20 AM

maybe that's a bit more detail than i needed.

can you provide a simple method for WHAT_IS_MAX_IP from IP_AND_MASK?

CLARIFICATION:
Do not need the long value of the mask.
Trying to determine max ip number allowable by specified range.