Which type of IP addresses are not globally unique and cannot communicate over the internet?

Private IP addresses are designated for use within local networks and are not routable over the internet. This means that any network device assigned a private IP address can communicate freely with other devices on the same local network but cannot directly send data to or receive data from the outside internet.

Private IP address ranges are defined by specific blocks within the IP addressing scheme specified in RFC 1918. These ranges include 10.0.0.0 to 10.255.255.255, 172.16.0.0 to 172.31.255.255, and 192.168.0.0 to 192.168.255.255. Because they are not globally unique, multiple networks can use the same private IP addresses without conflict. To communicate with the internet, devices using private IP addresses must go through a mechanism like Network Address Translation (NAT), which translates private IP addresses to a public IP address that can be used for internet communication.

Understanding the distinction between private and public IP addresses is crucial for networking, as it helps in designing and managing local networks while ensuring proper connectivity to the internet when needed.