::1/128 (IPv6 Loopback)
Not routableRFC 4291
::1/128 at a glance
| CIDR block | ::1/128 |
|---|---|
| First address | ::1 |
| Last address | ::1 |
| Total addresses | 2⁰ |
| Prefix mask | ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff |
| Prefix length | /128 |
| Type | Not routable |
| Publicly routable | No |
| Defined in | RFC 4291 |
What is ::1/128 used for?
::1 is the IPv6 loopback address, the equivalent of 127.0.0.1. Unlike IPv4, IPv6 reserves only this single address for loopback. Packets sent to ::1 never leave the host.
FAQ
What is ::1?
The IPv6 loopback address, the equivalent of 127.0.0.1. localhost usually resolves to both.
Why is there only one IPv6 loopback address?
IPv6 reserves a single /128 for loopback instead of a whole block, to avoid wasting space like IPv4's 127.0.0.0/8.