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FINANCIAL ANALYSTS & CPA REVIEWERS
About This Tool
Designing local area networks, configuring cloud virtual private clouds (VPCs), and setting up firewall routing tables requires calculating precise IP address boundaries and CIDR prefix blocks. This calculator performs bitwise IPv4 subnet math in real time, determining network addresses, broadcast addresses, usable host IP ranges, subnet masks, and wildcard inverse masks.
### Bitwise IPv4 Subnetting Principles The calculator evaluates 32-bit binary IPv4 address math directly in your browser: - **32-Bit Binary Address & Mask**: Converts dotted decimal octets into an unsigned 32-bit integer. A CIDR prefix like `/24` generates a 32-bit bitmask with 24 high bits (`0xFFFFFF00` or `255.255.255.0`). - **Network ID**: Computed via bitwise AND: `ipNum & maskNum`. This defines the root subnet base address. - **Broadcast Address**: Computed via bitwise OR with the inverted mask: `netNum | ~maskNum`. - **Wildcard Inverse Mask**: Negates the subnet mask (`~maskNum`), providing the inverse format required by Cisco ACLs and OSPF router configurations. - **Usable Host Capacity**: Total IP addresses equal `2^(32 - CIDR)`. For standard subnets (`/30` and larger), usable hosts equal `Total - 2` (excluding network and broadcast). For `/31` point-to-point links (RFC 3021), both addresses are usable.
### Worked Subnetting Example Given IP address **192.168.1.100** with a **/24 prefix** (24 net bits, 8 host bits): - **Subnet Mask**: `255.255.255.0` - **Wildcard Mask**: `0.0.0.255` - **Network Address**: `192.168.1.0` - **Broadcast Address**: `192.168.1.255` - **Usable Host Range**: `192.168.1.1` to `192.168.1.254` - **Host Counts**: 256 total IP addresses, with **254 usable host addresses**.
### Private Client-Side Calculation All binary conversions, bitwise shifts, and IP string formatting execute 100% inside your local web browser. No internal IP schemes, VPC topology, or network designs are transmitted across external networks.
How to Use
- 1
Enter any IPv4 address (e.g., 192.168.1.100 or 10.0.0.1) into the IP Address field.
- 2
Set your CIDR Prefix length (/1 to /32) using the prefix input.
- 3
Examine the resulting subnet mask, wildcard mask, network address, and broadcast address.
- 4
Review the first and last usable host IPs alongside total and usable host capacities.
Frequently Asked Questions
How does this calculator handle /31 point-to-point subnets?
In accordance with RFC 3021, /31 subnets do not reserve separate network and broadcast addresses, providing exactly 2 usable IP addresses for point-to-point router links.
What is a wildcard mask and where is it used?
A wildcard mask is the bitwise inverse of a subnet mask (where 0s match exact bits and 1s are wildcards), commonly required in Cisco IOS access control lists (ACLs) and OSPF network statements.
Are network IP addresses transmitted to any cloud server?
No. All IP bitwise math and octet splitting run entirely in client-side JavaScript memory.