/1 Subnet
2,147,483,648 total IPs — 2,147,483,646 usable hosts.
Example /1 Networks
| CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|
| 0.0.0.0/1 | 0.0.0.0 | 0.0.0.1 | 127.255.255.254 | 127.255.255.255 | 2,147,483,646 |
| 128.0.0.0/1 | 128.0.0.0 | 128.0.0.1 | 255.255.255.254 | 255.255.255.255 | 2,147,483,646 |
| 128.0.0.0/1 | 128.0.0.0 | 128.0.0.1 | 255.255.255.254 | 255.255.255.255 | 2,147,483,646 |
| 128.0.0.0/1 | 128.0.0.0 | 128.0.0.1 | 255.255.255.254 | 255.255.255.255 | 2,147,483,646 |
| 128.0.0.0/1 | 128.0.0.0 | 128.0.0.1 | 255.255.255.254 | 255.255.255.255 | 2,147,483,646 |
| 0.0.0.0/1 | 0.0.0.0 | 0.0.0.1 | 127.255.255.254 | 127.255.255.255 | 2,147,483,646 |
How /1 Compares
Frequently Asked Questions
How many IPs are in a /1?
A /1 subnet contains 2,147,483,648 total IP addresses and 2,147,483,646 usable host addresses. The network address (first IP) and broadcast address (last IP) are reserved and cannot be assigned to hosts.
What is the subnet mask for /1?
The subnet mask for a /1 is 128.0.0.0.
In CIDR notation, the prefix length /1 means
the first 1 bits of the address are the network portion.
The wildcard (inverse) mask is 127.255.255.255.
How many /1 subnets fit in a /0?
Exactly 2 — a /0 can be split into two /1 subnets of equal size. Each /1 subnet has 2,147,483,646 usable hosts, compared to 4,294,967,294 in the parent /0.