Architect your server networks safely. Instantly calculate complex CIDR boundaries, determine exact usable host ranges, and generate wildcard masks for firewall configurations.
Prevent IP conflicts and routing failures by mathematically proving your VPC boundaries before deployment.
The calculator accurately executes logical AND/OR operations against the 32-bit binary structure of your IP, guaranteeing flawless results for complex, non-standard subnets (like /23).
Automatically generate the inverted wildcard masks required by legacy Cisco networking gear and Access Control Lists (ACLs) to securely manage router traffic.
Never run out of IPs in the cloud. Instantly verify exactly how many physical servers or Docker containers can fit inside your proposed AWS Virtual Private Cloud (VPC) subnet.
Subnetting is the practice of dividing a massive, single network into smaller, logically separated networks (subnets). It is a fundamental skill for cloud architects and network engineers to optimize traffic flow, improve security, and prevent IP address exhaustion.
If a computer has the IP address 192.168.1.50, that string of numbers is actually divided into two distinct parts: the Network Portion (which identifies the office building) and the Host Portion (which identifies the specific computer inside the building).
A computer cannot inherently look at an IP address and know where the Network Portion ends and the Host Portion begins. It requires a Subnet Mask (like 255.255.255.0) to mathematically overlay on top of the IP address to reveal the boundary line.
Writing out 255.255.255.0 over and over again is tedious. Engineers use CIDR (Classless Inter-Domain Routing) notation to speed up communication.
When an engineer writes /24, they are stating that the first 24 bits of the 32-bit IP address are locked as the Network Portion.
Because 32 minus 24 equals 8, that leaves exactly 8 bits for the Host Portion. By using an online subnet calculator, you can instantly see that 28 gives you 256 total IPs. After subtracting the reserved Network and Broadcast addresses, you are left with exactly 254 usable IPs for your servers.
If you are building an application in Amazon Web Services (AWS), you must define the CIDR block for your Virtual Private Cloud (VPC) before you can deploy any servers.
/16 subnet to your database tier, you have allocated 65,000 IPs to a group that might only need 3 servers. This wastes valuable IP space and makes routing to other corporate offices difficult./28 subnet to your web-server tier, it only gives you 14 usable IPs. When your application goes viral, the auto-scaler will attempt to boot up a 15th server, crash because there are no IPs left, and take your website offline.