Types of 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 1st 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 1st 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 1st 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
