Private IP Address Ranges

• Class A: 10.0.0.0 — 10.255.255.255
• Class B: 172.16.0.0 — 172.31.255.255 
• Class C: 192.168.0.0 — 192.168.255.255 

Public IP Address Ranges

All public IP addresses belong to one of the following public IP address ranges:

• 1.0.0.0-9.255.255.255
• 11.0.0.0-100.63.255.255
• 100.128.0.0-126.255.255.255
• 128.0.0.0-169.253.255.255
• 169.255.0.0-172.15.255.255
• 172.32.0.0-191.255.255.255
• 192.0.1.0/24
• 192.0.3.0-192.88.98.255
• 192.88.100.0-192.167.255.255
• 192.169.0.0-198.17.255.255
• 198.20.0.0-198.51.99.255
• 198.51.101.0-203.0.112.255
• 203.0.114.0-223.255.255.255

The number in Class B addresses’ first octet ranges from 128 to 191. The number in Class A addresses’ first octet ranges from 1 to 126, and the number in Class C IP addresses’ first octet ranges from 192 to 223. See Book VIII, Chapter 3.

Class A

First octet starts from 1 and end at 126

Class B

First Octent starts from 128 and ends at 191

Class C

First Octent starts from 192 and ends at 223

APIPA Address

APIPA stands for Automatic Private IP Addressing, which is a feature of some operating systems, including Windows, that allows devices on a network to automatically assign themselves an IP address when a DHCP server is not available.

An APIPA address is a self-assigned IP address that is automatically generated by a device when it is unable to obtain an IP address from a DHCP server. The range of APIPA addresses is between 169.254.0.1 and 169.254.255.254. Devices that have an APIPA address can still communicate with other devices on the same network that also have an APIPA address.

It is important to note that APIPA addresses are meant to be temporary, and should not be used as a long-term solution. If a device is consistently unable to obtain an IP address from a DHCP server, it is recommended to investigate and resolve the root cause of the issue.