IPv4 addresses beginning with 127 are used for what type of addresses?

IPv4 addresses that begin with 127 are specifically designated for loopback addresses. The primary purpose of loopback addresses is to enable a computer to communicate with itself for testing and troubleshooting purposes. The most commonly used loopback address is 127.0.0.1, which is often referred to as "localhost."

When data is sent to a loopback address, it does not leave the local machine, allowing applications to communicate over the network stack without involving physical network interfaces. This functionality is useful for developers and network administrators as it allows for easy testing of network applications and services in a controlled environment.

While the other address types have their own specific uses—global addresses are used for public internet communication, private addresses are designated for use within private networks, and reserved addresses are set aside for special purposes—loopback addresses serve the distinct function of ensuring reliable internal communication for processes and services within the same host.