/0 Subnet: Mask 0.0.0.0, 4,294,967,294 Usable Hosts
A /0 subnet has a subnet mask of 0.0.0.0 and contains 4,294,967,296 total IP addresses, of which 4,294,967,294 are usable host addresses (the network and broadcast addresses are reserved). A /0 contains 16,777,216 /24 networks.
| CIDR notation | /0 |
|---|---|
| Subnet mask | 0.0.0.0 |
| Wildcard mask | 255.255.255.255 |
| Mask in binary | 00000000.00000000.00000000.00000000 |
| Total addresses | 4,294,967,296 (2^32) |
| Usable hosts | 4,294,967,294 |
| Host bits | 32 |
Usable hosts in a /0 by platform
Cloud providers reserve more than the usual two addresses per subnet, so the same /0 gives you fewer usable IPs in the cloud than on a standard LAN.
| Platform | Reserved IPs | Usable hosts |
|---|---|---|
| Standard (network + broadcast) | 2 | 4,294,967,294 |
| AWS VPC | 5 | 4,294,967,291 |
| Microsoft Azure VNet | 5 | 4,294,967,291 |
| Google Cloud VPC | 4 | 4,294,967,292 |
| Oracle Cloud VCN | 3 | 4,294,967,293 |
Good to know
A /0 represents the entire IPv4 address space, all 4.29 billion addresses. You see it as the default route (0.0.0.0/0) in routing tables, meaning "send anything I do not have a more specific route for here."
How a /0 is calculated
- The /0 means the first 0 bits are the network portion, leaving 32 host bits.
- Total addresses = 2^(32 - 0) = 2^32 = 4,294,967,296.
- Usable hosts (standard) = 4,294,967,296 - 2 (network + broadcast) = 4,294,967,294.
- Subnet mask = 0.0.0.0; wildcard mask = 255.255.255.255.
Want to split a /0 into smaller subnets, see every address range, or plan a VLSM layout? Open the free subnet calculator →