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IPv6 /128 prefix

A /128 leaves 0 bits for subnets and hosts: 1 address.

IPv6 /128 at a glance

Mask
ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Mask (expanded)
ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Host bits
0
Addresses
1
Nibble-aligned
Yes, the boundary falls on a hex digit
Reverse DNS zone
0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa

Typical uses of a /128

A /128 is one address. Use it for host routes, router loopbacks, ::1/128 (loopback), and firewall rules that allow exactly one IPv6 host.

Example: 2001:db8::/128

First address
2001:db8::
Last address
2001:db8::
Last (expanded)
2001:0db8:0000:0000:0000:0000:0000:0000
Next /128
2001:db8::1/128

Uses the documentation prefix 2001:db8::/32 (RFC 3849). IPv6 has no broadcast address, so every address in the range is assignable, except where a platform reserves some.

Find the /128 for an address

How many /128s fit

In aNumber of /128s
/3279,228,162,514,264,337,593,543,950,336
/481,208,925,819,614,629,174,706,176
/564,722,366,482,869,645,213,696
/6418,446,744,073,709,551,616

Cloud support for /128

PlatformIPv6 subnet size/128?
AWS VPC/44 to /64 in steps of /4No
Azure VNetexactly /64No
Google Cloud VPC/64 (from the VPC's /48)No