Loopback Address - ::1/128

::1/128 is the loopback address of the local host which is the equivalent of the in IPv4.  When an application in a specific host sends a data packet to this address, the TCIP/IP stack will loop the packet back on the same interface it was sent to so the packet never exits that host.

This type of address is mostly used for testing the TCP/IP stack as it only exists on that host and can't be reached by any other host on the network.

The first 127 bit of the loopback address is set to all 0's and the last bit set to 1 resulting an IP address that takes the form of 0:0:0:0:0:0:0:1:/128 or ::1/128 for short.