lecture2:IP classes

IP address space is divided into public and private spaces.

Private addresses are reserved IP addresses that are to be used only internally within a company’s network, not on the Internet.
public addresses designated for use in networks that are accessible on the Internet


RFC 1918, Address Allocation for Private Internets, defines the private IP addresses as follows:
10.0.0.0 to 10.255.255.255
172.16.0.0 to 172.31.255.255
192.168.0.0 to 192.168.255.255
The remaining addresses are public addresses.
*The network use private and public address
* A router or firewall act as the interface between the private and public IP address.
* Network Address Translation (NAT) or
*Port Address Translation (PAT)
*used to translate from private to public addresses and vice versa.
*NAT or PAT is required if accessibility to the public Internet or public visibility is required.
IPv4 addresses are categorized into five classes: A, B, C, D, and E.

Only Class A, B, and C addresses are used for addressing devices.

Class D is used for multicast groups.

Class E is reserved for experimental use.

This use of address space is referred to as classful addressing.