Detailed information about IPv4 /1 subnets
A /1 network is extremely large, allowing for millions of hosts. These are typically reserved for major infrastructure or internet service providers.
| CIDR Notation | /1 |
| Subnet Mask | 128.0.0.0 |
| Binary Subnet Mask | 10000000 00000000 00000000 00000000 |
| Total Addresses | 2,147,483,648 |
| Usable Hosts (Standard) | 2,147,483,646 |
| AWS Usable IPs | 2,147,483,641 |
| Azure Usable IPs | 2,147,483,641 |
| GCP Usable IPs | 2,147,483,642 |
A CIDR /1 subnet has 2,147,483,646 usable IP addresses for hosts. This is a relatively large subnet that can be further divided into smaller subnets if needed.
Organizations typically use subnets of this size for large-scale deployments or when planning for future growth.
Cloud providers reserve some IP addresses in each subnet for internal use, resulting in fewer usable IPs:
When planning your cloud infrastructure, consider these reserved addresses to accurately size your subnets.