/0 Subnet
Subnet Mask
Wildcard Mask
255.255.255.255
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
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 hosts in a /0 network?
A /0 network supports 4,294,967,294 usable hosts out of 4,294,967,296 total IP addresses. The usable range excludes the network address and broadcast address.
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.