Classful IP ADDRESSING-IPV4 Addressing in Network Layer

Classful IP ADDRESSING:-IPV4 Address is 32 bit address on internet that means four octants in IPV4 address each octant have 8 bit address. It can produce 4.29×10⁹ address space.

XXXXXXXX.XXXXXXXX.XXXXXXX.XXXXXXXX

There are four octants in IPV4 address each octant have 8 bit. Octants are seperated by . Dot operator.

Every Octant IP group have 256 address means range is from 0 (Zero) to 255.

255.255.255.255 (Maximum range of IP address).

IPV4 address divided into two part Network and Host part.

The subnet mask is a binary number that, when applied to an IP address, separates the network portion from the host portion.

1 bits in the subnet mask used for the network portion of the IP address.
0 bits in the subnet mask used for the host portion of the IP address.

Here we study about Classful IP addressing

The IP address splitted into 5 classes

Class A
Class B
Class C
Class D
Class E

The first octet of an IP address determines its class. Here’s a breakdown of the classes and their respective first octet ranges:

Class A:

Range: 1-126
Default subnet mask: 255.0.0.0
Network ID is 8 Bit long and Host ID 24 bit long.
No of N/W 2^8-1= 2⁷= 128
No of Host 2²⁴= 1677216
One bit (0) Reserve in Class A
Used for large networks

Two IP address are Special IP address in Class A

0.0.0.0: Applied to packets of unknown origin as a source IP address.

127.0.0.1: loop back address A unique IP address that points to the local host is called a loop back address. It doesn’t involve any external network traffic and is intended only for internal communication within a device.

So Useful range of Class A is 1.0.0.0 – 126.255.255.255

Class B:

Range: 128-191
Default subnet mask: 255.255.0.0
Network ID is 16 Bit long and Host ID 16 bit long.
No of N/W 2^16-2= 2¹⁴= 16384
No of Host 2¹⁶= 65536
Two bit (10) Reserve in Class B
Used for medium-sized networks

Class C:

Range: 192-223
Default subnet mask: 255.255.255.0
Network ID is 24 Bit long and Host ID 8 bit long.
No of N/W 2^24-3= 2²¹= 2097192
No of Host 2⁸= 256
Three bit (110) Reserve in Class C
Used for small networks

Class D:

Range: 224-239
Four bit (1110) Reserve in Class D
Reserved for multicast purposes

Class E:

Range: 240-255
Four bit (1111) Reserve in Class E
Reserved for experimental purposes

Unique Key points of Class D and E:

Class D:
Used for group communication/messages where a single packet can be sent to multiple recipients simultaneously.
Multicast addresses are not given to hosts i.e. given to groups of hosts.
Class E
Reserved for Experimental research development activities.
Not used for general use.