Question

Implement the following in Classless IP Addressing in C programming
(b) Implement Subnetting Concepts

Answer 1

Subnetting concept with C can be acheived using below code. Please execute and feel free to comment if you have any doubts.

I have attached the screenshot for the same at the end.

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#include <stdio.h>
#include <math.h>

int main(int argc, char *argv[]) {
  
  
printf(" Simple IP Subnet Calculator By dumiku ");

int IP1, IP2, IP3, IP4, CIDR, bitborrowed, bitremained, subnet, host, mask, blocksize;
char class;
  
//Request User input

printf("Please enter IP address in the form of "0.0.0.0": ");
  
scanf("%i.%i.%i.%i", &IP1, &IP2, &IP3, &IP4);
  
//Check if IP is valide
do
{
if((IP1 >255 || IP2 >255 || IP3 >255 || IP4 >255) || (IP1 == 127 || IP1 == 191 || IP1 == 255) || (IP1 == 0 && IP2 == 0 && IP3 == 0 && IP4 == 0))
{
  
printf(" Warning!! IP address invalid, please enter a valid IP address: ");
  
scanf("%d.%d.%d.%d", &IP1, &IP2, &IP3, &IP4);
}
}while((IP1 >255 || IP2 >255 || IP3 >255 || IP4 >255) || (IP1 == 127 || IP1 == 191 || IP1 == 255) || (IP1 == 0 && IP2 == 0 && IP3 == 0 && IP4 == 0));

//If IP valid ask for CIDR
  
printf("Enter CIDR in the format of decimal CIDR: ");
  
scanf("%d", &CIDR);
do{
//CHeck if CIDR is valid
if(CIDR > 32 || CIDR == 0)
{
  
printf("Invalid CIDR, please enter a valid CIDR: ");
  
scanf("%d", &CIDR);
}
}while(CIDR > 32);

//Let's determine IP class
if(IP1 <=170) {
class = 'A';
}else if(IP1 <=190) {
class = 'B';
}else {
class = 'C';
}
  
// Let find the number of bits borrowed
switch (class) {
case 'A':
if(CIDR >= 8) {
bitborrowed = CIDR - 8;
}else {
bitborrowed = 8 - CIDR;
}
break;
case 'B':
if(CIDR >= 16) {
bitborrowed = CIDR - 16;
}else {
bitborrowed = 16 - CIDR;
}
break;
case 'C':
if(CIDR >= 24) {
bitborrowed = CIDR - 24;
}else {
bitborrowed = 24 -CIDR;
}
}
  
//Let Find the number of bits that remained
switch (class) {
case 'A':
bitremained = 32 - CIDR;
break;
case 'B':
bitremained = 32 -CIDR;
break;
case 'C':
bitremained = 32 -CIDR;
break;
}
  
//Now Let Calculate the number of Subnets
subnet = pow(2,bitborrowed);
  
//And then we calculate the number of usable hosts
host = pow(2, bitremained)-2;
  
//Here we determine the block size
switch(bitborrowed) {
case 1:
blocksize = 128;
break;
case 2:
blocksize = 64;
break;
case 3:
blocksize = 32;
break;
case 4:
blocksize = 16;
break;
case 5:
blocksize = 8;
break;
case 6:
blocksize = 4;
break;
case 7:
blocksize = 2;
break;
case 8:
blocksize = 1;
break;
}
  
printf("Here is your Result: ");
  
  
printf("your IP %i.%i.%i.%i/%i is of class %c ", IP1,IP2,IP3,IP4,CIDR,class);

printf("Number of bit borrowed is: %d ", bitborrowed);
  
printf("Number of bits remained is: %d ", bitremained);
  
printf("Subnet: %d ", subnet);
  
printf("host: %d ", host);
  
printf("blocksize: %d ", blocksize);
return (0);
}

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