ipcalc.info

What It Is

ipcalc.info is a free IPv4 subnet calculator designed for networking and system administration scenarios. It accepts an IP address with a CIDR prefix, a dotted-decimal netmask, a Cisco wildcard mask, or just a plain IP address, then calculates the network address, broadcast address, Cisco wildcard mask, and host range. The page also provides reference tables for common CIDR prefixes, subnet masks, wildcard masks, and usable host counts.

Core Features and Documentation

In terms of functionality, it is more of a lightweight networking tool than a full IPAM or cloud network management platform. The main content clearly covers fundamentals such as IPv4 subnets, classful legacy address ranges, /31 point-to-point links, /32 host routes, and RFC1918 private addresses. The FAQ explains subnet masks, CIDR, wildcard masks, and network/broadcast addresses in a clear way, and cites standards including RFC 791, 950, 1918, 3021, and 4632. Overall, the documentation is friendly for both learning and quick reference.

Pricing and Openness

The page states that this is a free service hosted by Stackscale private cloud. There are no visible paid plans, account system, or advanced features. The crawled content does not show an open-source license, source code repository, self-hosting deployment method, API, SDK, CLI, or batch calculation interface. As a result, it is well suited for quick use in a browser, but not ideal for teams that need to integrate subnet calculations directly into automated workflows.

Pros and Cons

Its strengths are that it is free, requires no login, supports input formats commonly used in operations work, and can recognize inverse/wildcard netmasks, which is useful for Cisco ACL scenarios. The site also supports English and Spanish and includes light and dark themes. Its limitations are that the main content focuses on IPv4; although IPv6 appears in the navigation, the page does not provide detailed IPv6 functionality. It also lacks an SLA, support channels, a privacy statement, an API, and self-hosting options.

Who It’s For and Access from China

It is suitable for network engineers, system administrators, cloud infrastructure operations teams, and students learning CIDR, especially for quickly checking subnet plans, host counts, and wildcard conversions. Access from China cannot be determined from the available content and should be marked as unknown. If access is unstable, local command-line tools such as ipcalc/sipcalc, SubnetOnline, or cloud provider VPC subnet calculators can be considered as alternatives.