Network Calculator & Binary Visualizer
Calculate Network Subnet and see the binary representation.
Networking Reference
Subnetting: Logically dividing a network to reduce broadcast traffic and improve security boundaries.
ISP & Static IP Allocation: When businesses buy internet connections, providers often sell a "range of static IPs." It is critical to calculate the usable count correctly. For example, if a customer buys a /29 block (8 addresses), they only have 6 usable IPs for their servers, as the first and last are reserved for the Network and Broadcast addresses.
Usable Hosts: Calculated as $2^{(32-CIDR)} - 2$. The "minus two" accounts for:
- Network Address: The identifier for the subnet itself.
- Broadcast Address: Used to communicate with all devices in the range.
Common ISP Assignments
| CIDR | Total IPs | Usable for Customer |
|---|---|---|
| /30 | 4 | 2 (Point-to-Point) |
| /29 | 8 | 6 (Small Business) |
| /28 | 16 | 14 (Server Farm) |
Professional Tip
In a standard ISP handoff, the first usable IP is typically assigned to the ISP's gateway router, meaning the customer actually has 5 IPs left to assign to their own equipment in a /29.