IP Address Classes and Ranges Explained with Subnet Mask

By | March 29, 2013

There are two types of addressing in networking: Physical addressing and logical addressing. Physical address is the MAC address (Media access control) which is fixed for a particular computer. Logical address is the IP (Internet Protocol) address. In this CCNA tutorial, you will get to know Internet Protocol version 4 (IPv4) and different network classes explained in a simple way.

What is an IP address?

Network IP address is used to identify a host (PC or any network device) in a network. IP is a 32 bit binary number divided into 4 octet groups, each octet giving a maximum of 255 in decimal. For easier addressing of these IP address octet, they are written as dotted decimals.

Must Read: [Complete Guide] Class A IP Address, Subnet Mask, and Subnetting

Note: How to find out a host IP address? You can go for the command prompt IP address check by typing ipconfig as shown in the screenshot below

Classes of IP address in networking

IP is divided into 5 classes of network addresses based on the range of first octet.

Out of the total valid addresses in each class, two dedicated IP address is reserved for;

  1.  Network address
  2.  Broadcast address

So the total number of available IP addresses will  be
.

Public and Private IP addresses

To communicate over an internet, a device must have a public IP address which is provided by IANA (Internet Assigned Numbers Authority). Private range of IP addresses are used in an intranet (an internal network that uses internet technology). IANA also provides address for private networks in each class as follows:

Private Network Address Ranges in each Class

Before going in detail to IP classes we need to know about subnet masks and how to find subnet mask for IP addresses.

What is Subnet Mask?

If you’re a newbie to networking then the concept of Subnet mask may seem a little bit confusing, I also had a tough time struggling with subnet mask during my earlier days. By definition subnet mask is a 32 bit address used with an IP in order to identify its network and host portions.

Well, here I am going to put the simplest explanation for subnet mask. Please refer the network diagram below for better understanding. Let’s say you’ve got an IP address 200.1.1.2 with a subnet mask 255.255.255.0, it means that 200.1.1 is the network portion and last octet is the host portion. So any IP which starts with 200.1.1 goes to the same network (Network A), like 200.1.1.1, 200.1.1.10, 200.1.1.100 upto 200.1.1.254. And hence they don’t require a router to communicate with each other.

subnet mask explained

In Network A the first IP 200.1.1.0 is used to indicate network address and last IP 200.1.1.255 is used to send broadcast messages to all host computers in the network A.

Now another IP 200.1.2.2 which also has the same subnet mask cannot communicate with Network A without using a router because there’s a change in the network part. It belongs to another network with network address 200.1.2.0(Network B). Hope you got the point.

Another IP 10.1.1.2 with subnet mask 255.0.0.0 makes you understand that it belongs to the network 10.0.0.0(Network C), where only the first octet indicates network.

So subnet mask let’s you understand the IP belongs to which network. By default the following subnet masks are used.

Note:  All host bits ‘0’ is a network address.
All host bits ‘1’is a broadcast address.
Now let us see network classes A B C D of internet protocol a little deeper.

Network Class Ranges with Subnet Mask

Class A Network

Class A network range starts from 1.0.0.0 to 126.255.255.255. See the screenshot for easier understanding.

Class A network subnet mask is 255.0.0.0, which means it has 8 network bits of which the first bit is fixed as ‘0’. And hence a total of 7 network bits and 24 host bits.
Hence total no. of network will be

Here 2 is subtracted as 0.0.0.0 is the default network and 127.0.0.0 is the loopback ip address used for checking proper functionality (self testing).

And total number of hosts per network will be

Here 2 is subtracted for network and broadcast address.

Class A network example:

Network address -1.0.0.0
Subnet Mask -255.0.0.0
First host IP address -1.0.0.1
Last host address -1.255.255.254
Broadcast address -1.255.255.255

Class B Network

Now class B network range starts from 128.0.0.0 to 191.255.255.255. Default subnet mask is 255.255.0.0, which means it has 16 network bits of which first two bits are fixed as ‘10’. And hence a total of 14 network bits and 16 host bits.

So total no. of networks will be

And the total number of hosts per network will be

2 IP’s are subtracted, one each for network and broadcast address.

Let us take an example: 
Network address -128.0.0.0
Subnet Mask -255.255.0.0
First host address -128.0.0.1
Last host address -128.0.255.254
Broadcast address -128.0.255.255

Class C Network

IP range starts from 192.0.0.0 to 223.255.255.255. Class C network subnet mask is 255.255.255.0 that means it has 24 network bits of which the first three bits are fixed as ‘110’. So a total of 21 network bits and 8 host bits.
Hence total no. of network will be 
And the total number of hosts per network will be 

Here also 2 IP’s are subtracted, one for network and other for broadcast address.

Class C network example:

Network address -192.0.0.0
Subnet Mask -255.255.255.0
First host address -192.0.0.1
Last host address -192.0.0.254
Broadcast address -192.0.0.255

10 thoughts on “IP Address Classes and Ranges Explained with Subnet Mask

  1. Ty

    Thankyou so much for this. Every explanation I’ve read so far was overly complicated, but this explained it in a clear and simple way

    Reply
    1. Admin Post author

      Hi,
      You’re welcome, glad to know it helped you.

      Reply
  2. Bob

    Thanks! On the spot! Clean logically and progressively understandable. Nice work.

    Reply
  3. Admin Post author

    It’s great to see you here Bob, thanks for your valuable feedback. Keep visiting..

    Reply
  4. SD

    I’ve looked all over the internet for a clear explanation of subnetting but this is the only one that made sense. Great work, cheers.

    Reply
  5. k v satish kumar

    hi this is very very clear explanation , very very ……………….thank you .

    Reply
  6. Martin Bluck

    I was looking for an easy to understand explanation of the function of a subnet mask, this is great; thank you.

    Reply

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