What is the purpose of a loopback address?

• A. The routing of a signal from its origin back to the origin, primarily as a means of testing network connectivity.
• B. A public IP address used to identify a device on the internet.
• C. An address used to broadcast a packet to all hosts on a local network.
• D. An address used to select the default gateway for a device.

Answer: (B)

Loopback addresses are used to reach the same device from within itself, for testing and internal communication. In IPv4, the loopback range is 127.0.0.0/8, with 127.0.0.1 the most common. Sending a packet to a loopback address never leaves the host; it stays inside the machine and is processed by the local network stack. This lets you verify that the TCP/IP software and services are running correctly without needing another machine or a real network connection. It isn’t a public IP used to identify a device on the internet, and it isn’t used for broadcasting to all hosts or for selecting a default gateway.