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• Last Updated : 30 Apr, 2021

Given a valid IPv4 address in the form of string. The task is to determine class of given IPv4 address as well as separate Network and Host ID part from it.
Every host and router on internet has an IP address which encodes its network number and host number, combination of the two is unique. An IP address does not actually refer to a host but refers to a network interface, so if host is on two networks, it must have two IP addresses.
An address mask determines which portion of an IP address represents network number and which part represents host number, e.g., IP address, the mask has four octets. If a given bit of the mask is 1, the corresponding bit of the IP address is in network portion and if given bit of mask is 0, the corresponding bit of IP address is in host portion.

CIDR:
Classless Inter Domain Routing uses slash(/) notation to specify the mask with IPv4 address. The address is given as x.y.z.t/n where x.y.z.t is the IP address and n is the number of 1’s in the default mask.
First address of a network is network address. It is obtained by ANDing the mask with the IP address (Both in binary form). Another method is to set last 32-n bits of the IP address to 0.
Last address of a network is broadcast address. It is obtained by ORing the complement mask with the IP address(Both in binary form). Another method is to set last 32-n bits of the IP address to 1.
Class:
Class of an address is identified by the first byte of address. There are currently five classes A, B, C, D and E. The range of first byte of each class is:

```Class A: 0 - 127
Class B: 128 - 191
Class C: 192 - 223
Class D: 224 - 239
Class E: 240 - 255 ```

Example-1:

```CIDR: 192.168.32.1/24(x.y.z.t/n)

32-n=32-24=8

= 11000000101010000010000000000000
= 192.168.32.0

= 11000000101010000010000011111111
= 192.168.32.255  ```

Example-2:

```CIDR: 205.15.37.39/28(x.y.z.t/n)

32-n=32-28=4

= 11001101000011110010010100100000
= 205.15.37.32

= 11001101000011110010010100101111
= 205.15.37.47 ```

Implementation:
The following code uses the concepts mentioned above:

## C++

 `#include ``#include ``#include ``#include ``#include ` `using` `namespace` `std;``    ``// Converts IP address to the binary form``vector<``int``> bina(vector str)``    ``{``    ``vector<``int``> re(32,0);``        ``int` `a, b, c, d, i, rem;``        ``a = b = c = d = 1;``        ``stack<``int``> st;` `        ``// Separate each number of the IP address` `            ``a = stoi(str);``            ``b = stoi(str);``            ``c = stoi(str);``            ``d = stoi(str);` `        ``// convert first number to binary``        ``for` `(i = 0; i <= 7; i++)``        ``{``            ``rem = a % 2;``            ``st.push(rem);``            ``a = a / 2;``        ``}` `        ``// Obtain First octet``        ``for` `(i = 0; i <= 7; i++) {``            ``re[i] = st.top();``            ``st.pop();``        ``}` `        ``// convert second number to binary``        ``for` `(i = 8; i <= 15; i++) {``            ``rem = b % 2;``            ``st.push(rem);``            ``b = b / 2;``        ``}` `        ``// Obtain Second octet``        ``for` `(i = 8; i <= 15; i++) {``            ``re[i] = st.top();``            ``st.pop();``        ``}` `        ``// convert Third number to binary``        ``for` `(i = 16; i <= 23; i++) {``            ``rem = c % 2;``            ``st.push(rem);``            ``c = c / 2;``        ``}` `        ``// Obtain Third octet``        ``for` `(i = 16; i <= 23; i++) {``            ``re[i] = st.top();``            ``st.pop();``        ``}` `        ``// convert fourth number to binary``        ``for` `(i = 24; i <= 31; i++) {``            ``rem = d % 2;``            ``st.push(rem);``            ``d = d / 2;``        ``}` `        ``// Obtain Fourth octet``        ``for` `(i = 24; i <= 31; i++) {``            ``re[i] = st.top();``            ``st.pop();``        ``}` `        ``return` `(re);``    ``}` `    ``// cls returns class of given IP address``char` `cls(vector str)``    ``{``        ``int` `a = stoi(str);``        ``if` `(a >= 0 && a <= 127)``            ``return` `(``'A'``);``        ``else` `if` `(a >= 128 && a <= 191)``            ``return` `(``'B'``);``        ``else` `if` `(a >= 192 && a <= 223)``            ``return` `(``'C'``);``        ``else` `if` `(a >= 224 && a <= 239)``            ``return` `(``'D'``);``        ``else``            ``return` `(``'E'``);``    ``}` `    ``// Converts IP address``    ``// from binary to decimal form``vector<``int``> deci(vector<``int``> bi)``    ``{` `        ``vector<``int``> arr(4,0);``        ``int` `a, b, c, d, i, j;``        ``a = b = c = d = 0;``        ``j = 7;` `        ``for` `(i = 0; i < 8; i++) {` `            ``a = a + (``int``)(``pow``(2, j)) * bi[i];``            ``j--;``        ``}` `        ``j = 7;``        ``for` `(i = 8; i < 16; i++) {` `            ``b = b + bi[i] * (``int``)(``pow``(2, j));``            ``j--;``        ``}` `        ``j = 7;``        ``for` `(i = 16; i < 24; i++) {` `            ``c = c + bi[i] * (``int``)(``pow``(2, j));``            ``j--;``        ``}` `        ``j = 7;``        ``for` `(i = 24; i < 32; i++) {` `            ``d = d + bi[i] * (``int``)(``pow``(2, j));``            ``j--;``        ``}` `        ``arr = a;``        ``arr = b;``        ``arr = c;``        ``arr = d;``        ``return` `arr;``    ``}` `int` `main()``    ``{`  `        ``string ipr = ``"192.168.1.1/24"``;` `        ``// You can take user input here``        ``// instead of using default address``        ``// Ask user to enter IP address of form(x.y.z.t/n)``        ``cout<<``"IP address CIDR format is:"``<< ipr;` `        ``// Separate IP address and n``        ``string str1 = ``""``;``        ``int` `idx = 0;``        ``int` `len = ipr.size();``        ``len -= 3;``        ``while``(len--){``            ``str1 += ipr[idx];``            ``idx++;``        ``}``        ``cout< str;` `        ``string temp;``        ``int` `n = tr.size();``        ``for``(``int` `i = 0; i < n; i++){``            ``if``(tr[i] >= 48 && tr[i] <= 57)``                ``temp +=tr[i];``            ``else``{``                ``str.push_back(temp);``                ``temp = ``""``;``            ``}``        ``}``        ``str.push_back(temp);``        ``//cout< b;` `        ``cout< ntwk(32,0);``        ``vector<``int``> brd(32,0);``        ``int` `t = 32 - n;` `        ``// Obtanining network address``        ``for` `(``int` `i = 0; i <= (31 - t); i++) {` `            ``ntwk[i] = b[i];``            ``brd[i] = b[i];``        ``}` `        ``// Set 32-n bits to 0``        ``for` `(``int` `i = 31; i > (31 - t); i--) {` `            ``ntwk[i] = 0;``        ``}` `        ``// Obtaining Broadcast address``        ``// by setting 32-n bits to 1``        ``for` `(``int` `i = 31; i > (31 - t); i--) {` `            ``brd[i] = 1;``        ``}` `        ``cout< nt = deci(ntwk);` `        ``// Converting broadcast address to decimal``        ``vector<``int``> br = deci(brd);` `        ``// Printing in dotted decimal format``        ``cout<<``"First Address : "` `<< nt << ``"."` `<

## Java

 `import` `java.util.*;``import` `java.io.*;``import` `java.net.*;``import` `java.lang.Math;` `class` `Ip {``    ` `    ``// Converts IP address to the binary form``    ``public` `static` `int``[] bina(String[] str)``    ``{``        ``int` `re[] = ``new` `int``[``32``];``        ``int` `a, b, c, d, i, rem;``        ``a = b = c = d = ``1``;``        ``Stack st = ``new` `Stack();``        ` `        ``// Separate each number of the IP address``        ``if` `(str != ``null``)``        ``{``            ``a = Integer.parseInt(str[``0``]);``            ``b = Integer.parseInt(str[``1``]);``            ``c = Integer.parseInt(str[``2``]);``            ``d = Integer.parseInt(str[``3``]);``        ``}``        ` `        ``// convert first number to binary``        ``for` `(i = ``0``; i <= ``7``; i++)``        ``{``            ``rem = a % ``2``;``            ``st.push(rem);``            ``a = a / ``2``;``        ``}``        ` `        ``// Obtain First octet``        ``for` `(i = ``0``; i <= ``7``; i++) {``            ``re[i] = st.pop();``        ``}``        ` `        ``// convert second number to binary``        ``for` `(i = ``8``; i <= ``15``; i++) {``            ``rem = b % ``2``;``            ``st.push(rem);``            ``b = b / ``2``;``        ``}``        ` `        ``// Obtain Second octet``        ``for` `(i = ``8``; i <= ``15``; i++) {``            ``re[i] = st.pop();``        ``}``        ` `        ``// convert Third number to binary``        ``for` `(i = ``16``; i <= ``23``; i++) {``            ``rem = c % ``2``;``            ``st.push(rem);``            ``c = c / ``2``;``        ``}``        ` `        ``// Obtain Third octet``        ``for` `(i = ``16``; i <= ``23``; i++) {``            ``re[i] = st.pop();``        ``}``        ` `        ``// convert fourth number to binary``        ``for` `(i = ``24``; i <= ``31``; i++) {``            ``rem = d % ``2``;``            ``st.push(rem);``            ``d = d / ``2``;``        ``}``        ` `        ``// Obtain Fourth octet``        ``for` `(i = ``24``; i <= ``31``; i++) {``            ``re[i] = st.pop();``        ``}``        ` `        ``return` `(re);``    ``}``    ` `    ``// cls returns class of given IP address``    ``public` `static` `char` `cls(String[] str)``    ``{``        ``int` `a = Integer.parseInt(str[``0``]);``        ``if` `(a >= ``0` `&& a <= ``127``)``            ``return` `(``'A'``);``        ``else` `if` `(a >= ``128` `&& a <= ``191``)``            ``return` `(``'B'``);``        ``else` `if` `(a >= ``192` `&& a <= ``223``)``            ``return` `(``'C'``);``        ``else` `if` `(a >= ``224` `&& a <= ``239``)``            ``return` `(``'D'``);``        ``else``            ``return` `(``'E'``);``    ``}``    ` `    ``// Converts IP address``    ``// from binary to decimal form``    ``public` `static` `int``[] deci(``int``[] bi)``    ``{``        ` `        ``int``[] arr = ``new` `int``[``4``];``        ``int` `a, b, c, d, i, j;``        ``a = b = c = d = ``0``;``        ``j = ``7``;``        ` `        ``for` `(i = ``0``; i < ``8``; i++) {``            ` `            ``a = a + (``int``)(Math.pow(``2``, j)) * bi[i];``            ``j--;``        ``}``        ` `        ``j = ``7``;``        ``for` `(i = ``8``; i < ``16``; i++) {``            ` `            ``b = b + bi[i] * (``int``)(Math.pow(``2``, j));``            ``j--;``        ``}``        ` `        ``j = ``7``;``        ``for` `(i = ``16``; i < ``24``; i++) {``            ` `            ``c = c + bi[i] * (``int``)(Math.pow(``2``, j));``            ``j--;``        ``}``        ` `        ``j = ``7``;``        ``for` `(i = ``24``; i < ``32``; i++) {``            ` `            ``d = d + bi[i] * (``int``)(Math.pow(``2``, j));``            ``j--;``        ``}``        ` `        ``arr[``0``] = a;``        ``arr[``1``] = b;``        ``arr[``2``] = c;``        ``arr[``3``] = d;``        ``return` `arr;``    ``}``    ` `    ``public` `static` `void` `main(String args[])``    ``{` `        ``int` `i;``        ``String[] str = ``new` `String[``4``];``        ``String ipr = ``"192.168.1.1/24"``;` `        ``// You can take user input here``        ``// instead of using default address``        ``// Ask user to enter IP address of form(x.y.z.t/n)``        ``System.out.println(``"IP address CIDR format is:"` `+ ipr);``        ` `        ``// Separate IP address and n``        ``String[] str1 = ipr.split(``"/"``);``        ` `        ``// IP address``        ``String tr = str1[``0``];``        ` `        ``// Split IP address into 4 subparts x, y, z, t``        ``str = tr.split(``"\\."``);` `        ``int``[] b = ``new` `int``[``32``];` `        ``System.out.println();``        ` `        ``// Convert IP address to binary form``        ``b = bina(str);` `        ``int` `n = Integer.parseInt(str1[``1``]);``        ``int``[] ntwk = ``new` `int``[``32``];``        ``int``[] brd = ``new` `int``[``32``];``        ``int` `t = ``32` `- n;``        ` `        ``// Obtanining network address``        ``for` `(i = ``0``; i <= (``31` `- t); i++) {``            ` `            ``ntwk[i] = b[i];``            ``brd[i] = b[i];``        ``}``        ` `        ``// Set 32-n bits to 0``        ``for` `(i = ``31``; i > (``31` `- t); i--) {``            ` `            ``ntwk[i] = ``0``;``        ``}``        ` `        ``// Obtaining Broadcast address``        ``// by setting 32-n bits to 1``        ``for` `(i = ``31``; i > (``31` `- t); i--) {``            ` `            ``brd[i] = ``1``;``        ``}``        ` `        ``System.out.println();` `        ``// Obtaining class of Address``        ``char` `c = cls(str);``        ``System.out.println(``"Class : "` `+ c);``        ` `        ``// Converting network address to decimal``        ``int``[] nt = deci(ntwk);``        ` `        ``// Converting broadcast address to decimal``        ``int``[] br = deci(brd);` `        ``// Printing in dotted decimal format``        ``System.out.println(``"Network Address : "` `+ nt[``0``]``                     ``+ ``"."` `+ nt[``1``] + ``"."` `+ nt[``2``] + ``"."` `+ nt[``3``]);``        ` `        ``// Printing in dotted decimal format``        ``System.out.println(``"Broadcast Address : "``                     ``+ br[``0``] + ``"."` `+ br[``1``] + ``"."` `+ br[``2``] + ``"."` `+ br[``3``]);``    ``}``}`

Output:

```IP address CIDR format is:192.168.1.1/24

Class : C