• सुखार्थी त्यजते विद्यं विध्यार्थी त्यजते सुखम्सु sखर्थीन: कुतॊ विद्या कुतॊ विध्यार्थीन: सुखम् ||
  • “Luxury people leave knowledge, but a student leaves Luxury No knowledge for one who seeks Luxury, No luxury for student”
  • न चोर हार्यं न च राज हार्यं न भात्रू भाज्यं न च भारकारि |व्ययं कृते वर्धत एव नित्यं विद्याधनं सर्वधनप्रधानम ||
  • Cannot be snatched away by thief, cannot be snatched away by king, Cannot be divided among brothers, Not heavy either If spent daily, it always keeps growing. The wealth of knowledge is the precious of wealth of all”

Classful Addressing




Classful Addressing System.

In Classful Addressing System, IP Addresses are organized into following 5 classes-

  1. Class A     Assigned to large organizations.
  2. Class B    Assigned to medium sized organizations.
  3. Class C   Assigned to small sized organizations.
  4. Class D   Used for multicasting and broadcasting.
  5. Class E    Reserved for experimental purpose and future use.

Class A Adresses

The first bit of the first octet of class A address is always set to 0 (zero). As first bit of first octet is always 0, there can be 231 possible addresses in class A. Thus it contains 50% of the total IP addresses available in IP-version 4. 

Class A addresses only include IP starting from 1.X.X.X to 126.X.X.X only. The IP range 127.X.X.X is reserved for loopback IP addresses. The default subnet mask for Class A IP address is 255.0.0.0 which implies that Class A addressing can have 126 networks (27-2) and 16777214 hosts (224-2). Two addresses from the range are reserved as Network ID and Broadcast ID.

Class A IP format : 

0NNNNNNN.HHHHHHHH.HHHHHHHH.HHHHHHHH

where N represents Network bit and H represents Host bit


Class B Addresses

The first two bits of first octet of class B address is always set to 10 . As first two bits of first octet is always 10, there can be 230 possible addresses in class B. Thus it contains 25% of the total IP addresses available in IP-version 4. 

Class B IP Addresses range from 128.0.X.X to 191.255.X.X. The default subnet mask for Class B is 255.255.X.X.

Class B has 16384 (214) Network addresses and 65534 (216-2) Host addresses.

Class B IP address format : 

10NNNNNN.NNNNNNNN.HHHHHHHH.HHHHHHHH


Class C Addresses

The first three bits of first octet of class C address is always set to 110 . As first three bits of first octet is always 110, there can be 229 possible addresses in class C. Thus it contains 12.5% of the total IP addresses available in IP-version 4. 

Class C IP addresses range from 192.0.0.X to 223.255.255.X. The default subnet mask for Class C is 255.255.255.X.

Class C gives 2097152 (221) Network addresses and 254 (28-2) Host addresses.

Class C IP address format :

 110NNNNN.NNNNNNNN.NNNNNNNN.HHHHHHHH


Class D Address

The first four bits of first octet of class D address is always set to 1110 . As first four bits of first octet is always 1110, there can be 228 possible addresses in class D. Thus it contains 6.25% of the total IP addresses available in IP-version 4. 

Class D has IP address range from 224.0.0.0 to 239.255.255.255. Class D is reserved for Multicasting. In multicasting data is not destined for a particular host, that is why there is no need to find host address from the IP address, and Class D does not have any subnet mask.

Class E Addresses

The first four bits of first octet of class E address is always set to 1111 . As first four bits of first octet is always 1111, there can be 228 possible addresses in class D. Thus it contains 6.25% of the total IP addresses available in IP-version 4. 

This IP Class is reserved for experimental purposes and future use. IP addresses in this class ranges from 240.0.0.0 to 255.255.255.254. Like Class D, there is no need to find host address from the IP address, thus it does not have any subnet mask.