Special IPv4 addresses

Unique addresses which have special purposes, either on the internet or the private network, exist. In this section, we'll provide a list of these special addresses, along with their purposes.

Loopback addresses

The loopback address is used by a host to send traffic to itself. The loopback address ranges from 127.0.0.1 /8 to 127.255.255.254/8. A simple example of using the loopback address is to check whether the TCP/IP stack is working properly on a local system. Network professionals usually ping the address, that is, 127.0.0.1:

C:\>ping 127.0.0.1

Pinging 127.0.0.1 with 32 bytes of data:
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply...