A company can use private IPs on its private networks
IEEE recommends the following:
10.0.0.0 through 10.255.255.255.255
172.16.0.0 through 172.31.255.255
192.168.0.0 through 192.168.255.255
Classes
Dividing line between network and host portions is determined by numerical range IP address falls in
Class A, B, and C are available for use on the internet
Public IP addresses
Classes D and E are not available for general use:
Class D begins with octets 224-239 --> use for multicasting
Class E begins with octets 240-254 --> used for research
Class
Network octets
Octet Range
Default Mask
Approx. number of possible networks
Approx. number of IP aπddresses in each network
A
1.x.y.z to 126.x.y.z
1-126
255.0.0.0
126
16 million
B
128.0.x.y to 191.255.x.y
128-191
255.255.0.0
16,000
65,000
C
192.0.0.x to 223.255.255.x
192-223
255.255.255.0
2 million
254
Reserved IPs
IP Address(es)
Function
255.255.255.255
Used to broadcast messages by TCP/IP background processes. Message is read by every node on the network.
0.0.0.0
Unassigned
127.0.0.1 through 127.255.255.254
Uses for research or your own computer (loopback address)
169.254.0.1 through 169.254.255.254
Used to create APIPA address when a computer configured for DHCP first connects to the network and is unable to lease an IPv4 address from DHCP server.