LEARN PHYSICS AND TELECOMMUNICATION TECHNOLOGY FREE EASY TIPS FOR YOU HERE LATEST POST PUBLISHED"ESCAPE VELOCITY CONCEPTS" WAIT FOR NEW

## Saturday, 31 March 2018

Today our topic is about subnet mask, This topic is important and interesting, most of the people confused in subnet mass, Because their concepts is not clear and always in doubt,  How much you know about subnet mask i don't know, But i ensure you after complete reading of this post your concept and all doubt will be clear forever in easy way. In previous post we have discussed in details about IP concepts, In subnet mask that concept will be use so i will suggest you to refer first IP concepts post after that you can well understand subnet mask. So lets start this topic.

### subnet mask explained

Subnetting is a technique to use IP addresses efficiently or preserved IP addresses with minimum wastage of IP addresses. To do this we have only three methods.

1 Use private IP, We know private IP for class A 10.0.0.0 for class B 172.16.x.x and for class C 192.0.0.0

2 Use IPv6 where unlimited IP are available no shortage for whole globe 128 bits, remember in IPv4 only 32 bits available.

3 Use Subnetting.

Hence here we will use subnetting concept to find subnet mask, The meaning of subnetting is "network within a network" or logically division of IP addresses,To understand why subnetting is required take an example to well explain the concept of subnetting see below picture.

### subnet mask calculator

Allocate 10 users group Class A IP address 10.0.0.0          network ID (10.0.0.0)

Allocate 50 users group class B IP address 130.10.0.0       network ID (130.10.0.0)

Allocate 4 users group class C IP address 200.10.11.0       network ID (200.10.11.0)

Allocate 20 users group class C IP address 200.10.10.0     network ID (200.10.10.0)

Now you can see clearly all network ID are different for every router interface well .

# tags Allocate 10 users group Class A IP address 10.0.0.0          network ID (10.0.0.0)
Now you will allocate 10 users IP like.
1 → 10.0.0.1
2 → 10.0.0.2
3 → 10.0.0.3
4 → 10.0.0.4
5 → 10.0.0.5
6 → 10.0.0.6
7 → 10.0.0.7
8 → 10.0.0.8
9 → 10.0.0.9
10 → 10.0.0.10

Above IP address are allocated to 10 users. Can you think how much more IP address you can provide to users from this network ID. If you can recall from previous post then you will find for class A three octet are reserved for host that is 24 bits.
Its means that you can connect total number of users to this network ID will be (2²⁴ -2) it will be a very large number. it will approx to 16 Lakhs.
But you have only allocated 10 users, Then think about the rest IP addresses which is not used. Can we use rest IP addresses to other router interface BIG no, As discussed above all different router interface must have different network ID.
Now maximum you will use 100 to 200 users not even one Lakhs, Then you are wastage  IP addresses of class A.
Now take similarly for class B.

# tags Allocate 50 users group class B IP address 130.10.0.0       network ID (130.10.0.0)
You will allocate 50 users IP addresses like.

1 → 130.10.0.1 and 50th user 130.10.0.50 but think how many more users can connect in this network ID. This is class B hence two octet reserved for host so total number of users can be (2¹⁶ -2) which will be equal to 65,534. This much of computer can be connect, But we are connecting only 50 computer again this is wastage of IP address of class B.
Now take for class C.

# tags Allocate 4 users group class C IP address 200.10.11.0       network ID (200.10.11.0)
similarly allocate 4 users IP addresses like

1 → 200.10.11.1 and 4th user 200.10.11.4 but think how much more computer can be connected on this network ID.This is class C hence one octet is reserved for host so we can connect total number of computer here (2⁸ -2) it will be equal to 254.But we are only connecting 4 computer. Again wastage of IP addresses of class C but little bit less compare to class A and B.

Hence to save the wastage of these IP addresses we apply technique such that the same network can be divided into sub network and maximum IP addresses can be used and router don't understand that is same network need subnetting.

One important point CIDR value for all classes A, B, C respectively 10.0.0.0/8
130.10.10.0/16  200.10.10.0/24 if it is written by default it means that no any subnetting has been done. Except this number 8,16, 24 if any number written then subnetting has been done.

Now we will continue this topic in next post.I hope you have enjoyed learning Subnet mass concepts. If you like please share social media and comments.
Thanks for reading and sharing keep reading more and more.
Dated 21st Oct 2018