/0 Subnet
A /0 has the subnet mask 0.0.0.0 and contains 4,294,967,296 IP addresses, of which 4,294,967,294 are usable hosts. Every other prefix is in the subnet cheat sheet.
Subnet Mask
Wildcard Mask
Total IPs
4,294,967,296
Usable Hosts
4,294,967,294
Network Bits
0
Host Bits
32
About /0 Networks
Default route — matches all IPv4 addresses. A /0 subnet uses the mask 0.0.0.0 and provides 4,294,967,294 usable host addresses out of 4,294,967,296 total IPs.
Example /0 Networks
Splitting a /0 Into Smaller Subnets
A /0 divides evenly into any longer prefix. Each row shows how many subnets of that size fit inside one /0, and how many usable hosts each of them carries.
| Subnet Size | How Many Fit | Mask | Usable Hosts Each |
|---|---|---|---|
| /1 | 2 × /1 | 128.0.0.0 | 2,147,483,646 |
| /2 | 4 × /2 | 192.0.0.0 | 1,073,741,822 |
| /3 | 8 × /3 | 224.0.0.0 | 536,870,910 |
| /4 | 16 × /4 | 240.0.0.0 | 268,435,454 |
| /5 | 32 × /5 | 248.0.0.0 | 134,217,726 |
| /6 | 64 × /6 | 252.0.0.0 | 67,108,862 |
| /7 | 128 × /7 | 254.0.0.0 | 33,554,430 |
| /8 | 256 × /8 | 255.0.0.0 | 16,777,214 |
| /9 | 512 × /9 | 255.128.0.0 | 8,388,606 |
| /10 | 1,024 × /10 | 255.192.0.0 | 4,194,302 |
| /11 | 2,048 × /11 | 255.224.0.0 | 2,097,150 |
| /12 | 4,096 × /12 | 255.240.0.0 | 1,048,574 |
| /13 | 8,192 × /13 | 255.248.0.0 | 524,286 |
| /14 | 16,384 × /14 | 255.252.0.0 | 262,142 |
| /15 | 32,768 × /15 | 255.254.0.0 | 131,070 |
| /16 | 65,536 × /16 | 255.255.0.0 | 65,534 |
| /17 | 131,072 × /17 | 255.255.128.0 | 32,766 |
| /18 | 262,144 × /18 | 255.255.192.0 | 16,382 |
| /19 | 524,288 × /19 | 255.255.224.0 | 8,190 |
| /20 | 1,048,576 × /20 | 255.255.240.0 | 4,094 |
| /21 | 2,097,152 × /21 | 255.255.248.0 | 2,046 |
| /22 | 4,194,304 × /22 | 255.255.252.0 | 1,022 |
| /23 | 8,388,608 × /23 | 255.255.254.0 | 510 |
| /24 | 16,777,216 × /24 | 255.255.255.0 | 254 |
| /25 | 33,554,432 × /25 | 255.255.255.128 | 126 |
| /26 | 67,108,864 × /26 | 255.255.255.192 | 62 |
| /27 | 134,217,728 × /27 | 255.255.255.224 | 30 |
| /28 | 268,435,456 × /28 | 255.255.255.240 | 14 |
| /29 | 536,870,912 × /29 | 255.255.255.248 | 6 |
| /30 | 1,073,741,824 × /30 | 255.255.255.252 | 2 |
| /31 | 2,147,483,648 × /31 | 255.255.255.254 | 2 |
| /32 | 4,294,967,296 × /32 | 255.255.255.255 | 1 |
Adjacent CIDRs
Comparing sizes? The full /0 to /32 cheat sheet table puts every prefix side by side.
Frequently Asked Questions
What is a /0 subnet?
A /0 subnet uses the subnet mask 0.0.0.0 with 4,294,967,294 usable host addresses and 4,294,967,296 total IP addresses. It has 0 network bits and 32 host bits.
How many IP addresses are in a /0?
A /0 contains 4,294,967,296 IP addresses, of which 4,294,967,294 are usable hosts. The network address and the broadcast address are the two that cannot be assigned to a host.
What subnet mask does /0 use?
A /0 subnet uses the mask 0.0.0.0 (wildcard mask 255.255.255.255). This means the first 0 bits identify the network and the remaining 32 bits identify hosts.
How many /2 subnets are in a /0?
One /0 splits into 4 /2 subnets, each with mask 192.0.0.0 and 1,073,741,822 usable hosts. Every prefix longer than /0 divides it evenly — the full table is above.
Standards
The figures on this page follow from the following specifications rather than from convention.
- RFC 4632 — Classless Inter-Domain Routing (CIDR)
Defines the /0 prefix notation used throughout this page, and the address-aggregation model that replaced classful addressing.
- RFC 950 — Internet Standard Subnetting Procedure
The original definition of the subnet mask, and of the network and broadcast addresses excluded from the usable host count.