127.1 is a valid IP address, all fields that are 0 "in the middle" can be removed, same will go for ipv6 where it's gonna be neccessary

$ ping 127.1
PING 127.1 (127.0.0.1) 56(84) bytes of data.
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.025 ms

And I'm not sure about this, but it works for ping too:

ping 0x7f000001
PING 0x7f000001 (127.0.0.1) 56(84) bytes of data.
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.026 ms