/32 · 255.255.255.255
Open in the calculator
A single address. /32 is how you write one host in a route, a firewall rule or an allowlist (203.0.113.7/32). Loopback and anycast service addresses are also announced as /32s.
Key numbers
| Prefix length | /32 (32 network bits, 0 host bits) |
| Subnet mask | 255.255.255.255 |
| Mask in binary | 11111111.11111111.11111111.11111111 |
| Wildcard mask | 0.0.0.0 |
| Total addresses | 1 |
| Usable hosts | 1 (single host) |
| Fits in a /24 | 256 times |
| Block size | Increments of 1 in octet 4 |
Example ranges
Private (RFC 1918) blocks of this size. Click one to open it in the calculator.
| Block | First address | Last address | Usable hosts |
|---|---|---|---|
| 10.0.0.0/32 | 10.0.0.0 | 10.0.0.0 | 10.0.0.0 – 10.0.0.0 |
| 172.16.0.0/32 | 172.16.0.0 | 172.16.0.0 | 172.16.0.0 – 172.16.0.0 |
| 192.168.0.0/32 | 192.168.0.0 | 192.168.0.0 | 192.168.0.0 – 192.168.0.0 |
Usable addresses in the cloud
Cloud providers reserve a few addresses in every subnet for the router, DNS and future use, so the usable count is lower than the formula gives.
| Provider | Usable in a /32 | Notes |
|---|---|---|
| AWS VPC subnet | n/a | Not allowed: AWS subnets must be between /16 and /28. |
| Azure virtual network subnet | n/a | Not allowed: /29 is the smallest Azure subnet. |
| Google Cloud subnet | n/a | Not allowed: /29 is the smallest primary range. |
How the numbers are derived
An IPv4 address has 32 bits. A /32 uses 32 of them for the network, leaving 0 host bits, so the block has 20 = 1 addresses. The subnet mask is 32 ones followed by 0 zeros, written in dotted decimal as 255.255.255.255; the wildcard mask 0.0.0.0 is its inverse, used in Cisco ACLs and OSPF configuration.
FAQ
How many hosts can a /32 have?
One. A /32 identifies a single address.
How many /32 subnets fit in a /24?
256. A /24 has 256 addresses and a /32 has 1, so 256 ÷ 1 = 256 blocks.