IPv4 - Internal Host Loopback Address Range
The 127.0.0.0/8 address range is called the Internal host loopback address range. IPv4 addresses of this form are used to refer to the host itself. If you were to ping any of these addresses on any network device, you should get a response. This is because these addresses refer to the local host.
In practice, any ping to an IP address of 127.0.0.1 all the way up to 127.255.255.254 will have a response from the local host assuming that the IP protocol stack (the interface itself, that is) is up and running. Now theoretically, the 127.0.0.0 and 127.255.255.255 addresses are reserved for network and broadcast respectively, however, in practice, these have no meaning in the context of the local loopback. Indeed if you try pinging 127.0.0.0 on a PC, you will get a general failure message. Similarly, you will get no response from 127.255.255.255. So these addresses in reality are meaningless in this context.
The IPv6 - loopback address is defined as ::1/128.
Links
https://forum.networklessons.com/t/ip-internet-protocol-version-4-for-ccna-r-s/1108/47?u=lagapides