t-h2o / net-bc

Use bc for creating a IP table

BC

Table of Contents

• Print a table
  • The IP table
  • Mask to decimal
  • bc function

The goal of this repository is to print a table with the bc calculator.

Print a table

The IP table

Print a table similar to this:

Mask	Binary	Decimal
/0	0000 0000	0
/1	1000 0000	128
/2	1100 0000	192
/3	1110 0000	224
/4	1111 0000	240
/5	1111 1000	248
/6	1111 1100	252
/7	1111 1110	254
/8	1111 1111	255

The adresses being written on 4 bytes, the table should look like the following :

Mask	Decimal
/24	255.255.255.0
/25	255.255.255.128
/26	255.255.255.192
/27	255.255.255.224
/28	255.255.255.240
/29	255.255.255.248
/30	255.255.255.252
/31	255.255.255.254
/32	255.255.255.255

Mask to decimal

\$decimal(mask) = 256 - 2 ^ ((8 - mask))\$

bc function

define void all_ranges() {
  for ( index = 1; index < 8; ++index)
  {
    print "/", index, " - ", (256 - 2 ^ (8 - index)), "\n";
    x = 0;
    gap = 2 ^ (8 - index);
    while (x < 256)
    {
      print "\t", x, " - ", x + gap - 1, "\n";
      x = x + gap;
    }
  }
  return ;
}

mask and byte

This function takes two arguments, a mask [1-8] and a byte [0-255], that print informations.

Example:

mask_byte(4, 42)
mask : 4
byte : 42
mask: /4 -> decimal: 240
Network  : 32
host min : 33
host max : 46
Broadcast: 47

define void mask_byte(mask, byte) {
  print "mask : ", mask, "\n";
  print "byte : ", byte, "\n";

  gap = 2 ^ (8 - mask);
  decimal = 256 - gap
  print "mask: /", mask, " -> decimal: ", decimal, "\n";

  network = 0;
  while (network < 256)
  {
    broadcast = network + gap - 1;
    if (byte <= broadcast)
      break ;

    network = network + gap;
  }

  if (mask == 8)
  {
    host_min = network;
    host_max = broadcast;
  }
  if (mask != 8)
  {
    host_min = network + 1;
    host_max = broadcast - 1;
  }

  print "Network  : ", network, "\n";
  print "host min : ", host_min, "\n";
  print "host max : ", host_max, "\n";
  print "Broadcast: ", broadcast, "\n\n";

  return ;
}