Masking and IP Addressing format

Types of Addressing

• Classful Addressing
• Classless Addressing

Classful Addressing

•  IPv4 uses concept of classes. This architecture is called classful addressing.

               

•  Types of Classes

                                Class A, B, C, D, and E.

•  In Classful addressing, a large part of available addresses were wasted.

               

•  IPv4 Addresses are divided into two parts

                                Netid ( Network ID ) defined by IANA (Internet Assigned Number Authority)

                                Hostid ( Host ID ) defined by ISP (Internet Service Provider)

From the above diagram

Class A

•   First 8 bits are Netid and rest 24 bits are Hostid

•   Each Hostid varies from 0-255 => 256 Nodes

•   Subnet Mask is 255.*.*.* or 255.0.0.0

•   Total No. of nodes can be connected = 256 * 256 * 256 = 16,777,216

•   IPv4 Netid Range Varies: 0 - 127

                Eg.  10.0.0.0/8  - Starting and Ending IP Range 

• Mask is over only 1^st 8 bits

• That means only first 8 bits (Netid) are fixed (varies from 0-127) assigned by IANA (Internet Assigned Number Authority) for Big Organizations having large no. of hosts attached.

• Rest 24-Bits (3-Bytes Hostid) can vary from (0-255) 

• It implies that with single Netid there can be (256*256*256 = 16,777,216) nodes attached

             

Class B

•    First 8 bits are Netid and rest 24 bits are Hostid

•    Each Hostid varies from 0-255 => 256 Nodes

•    Subnet Mask is 255.255.*.* or 255.255.0.0

•    Total No. of nodes can be connected = 256 * 256 = 65,536

•    IPv4 Netid Range Varies: 128-191

                Eg.  172.16.0.0/16  - Starting and Ending IP Range 

• Mask is over only 1^st 16 bits

• That means only first 8 bits (Netid) are fixed (varies from 0-127) next 8 bits can be varying from (1-255) 

• These 16-Bits (2 Bytes Netid) are defined by IANA (Internet Assigned Number Authority) for mid size organizations with around ten thousands of hosts or router are attached

• Rest 16-Bits (Hostid) can vary from (0-255)

• It implies that with single Netid there can be (256 * 256 = 65,535)

Class C

•    First 8 bits are Netid and rest 24 bits are Hostid

•    Each Hostid varies from 0-255 => 256 Nodes
     
•    Subnet Mask is 255.255.255.* or 255.255.255.0

•    Total No. of nodes can be connected = > (0 to 255) = 256

•    IPv4 Netid Range Varies: 192-223

                Eg.  192.168.1.0/24 - Starting and Ending IP Range 

• Mask is over only 1^st 24 bits\

• That means only first 8 bits (Netid) are fixed (varies from 192-223) next 16 bits can be varying from (1-255)

• These 24-Bits (3 Bytes Netid) are defined by IANA (Internet Assigned Number Authority) for small organizations with a small number of hosts attached

• Rest 8-Bits (Hostid) can vary from (0-255) 

• It implies that with single Netid there can be only (256) nodes attached

IP Addressing Part 1 IP Addressing Part 2