Can U look at an IP addresses and guess whether it belongs to a private network or is on the internet? The answer is yes.
The Internet Assigned Numbers Authority (IANA) has reserved thefollowing three blocks of the IP address space for private networks:
10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255
Earlier the IP range was divided as ClassA, ClassB , Class C etc. but now we have CIDR (Class less inter-domain routing) which allows us to slice and dice networks the way we want to.