IPv4 Address Classes

• IPv4 Classfull Address is the address with the default mask.

• Classless Address (CIDR) is the address with any other mask but not the default mask.

• Classfull Address was used from 1981 until the introduction of Classless Addresses (CIDR) in 1993.

  Classfull Addresses were divided into 5 Classes:

• Class A - used for Unicast Traffic

• Class B - used for Unicast Traffic

• Class C - used for Unicast Traffic

• Class D - used for Multicast Traffic

• Class E - Reserved for future/experimental purposes.

• Class A, B & C were used to accommodate different sizes of Networks which aided in the classifications of the Networks.

• Addresses Classes are determined & allocated by the IANA.

Reference:

• https://www.udemy.com/course/cisco-ccent-icnd1-100-105-complete-course-sims-and-gns3/learn/lecture/6087452#overview