My Little Network Professor

The Little Network Professor'sIPv4 Toolkit

This collection of tools helps you work confidently with IPv4 addresses, subnets, and networks. The tools are not only meant to give answers, but also to show how subnetting works. Useful as a reference, a learning aid, or for everyday work.

IPv4 Calculator Does an IPv4 fall within the subnet? Subnet Mask ↔ CIDR VLSM (subnet splitting) Supernetting Decimal ↔ Binary Port Number → Service DNS Tool Calculate a network address with bitwise AND

IPv4 Calculator

This tool calculates network information from an IPv4 address in CIDR notation. You will see the subnet mask, network address, broadcast address, number of (usable) hosts, and the IP class.

Does an IPv4 fall within the subnet?

This tool checks whether an IP address falls within a given subnet. Enter the subnet as 192.168.1.0/24 or as 192.168.1.0 255.255.255.0. The tool compares both with a bitwise check and tells you whether the IP is in range.

Subnet Mask ↔ CIDR

This converter turns a subnet mask (like 255.255.255.0) into CIDR notation (/24), or the other way around. You also get the binary representation so you can see how subnetting works under the hood.

VLSM (Variable Length Subnet Masking)

With VLSM you can split a larger network block (for example a /22) into subnets of different sizes, depending on how many hosts you need per subnet. A subnet can also be a /24 if you need around 200 hosts. The tool automatically chooses the smallest possible subnet that is large enough. As long as the total number of IP addresses fits within the original block, you can create multiple subnets of different sizes, including one or more /24s.

Supernetting

This tool checks whether multiple IPv4 subnets can be merged into one larger network: a supernet. This only works if the subnets are contiguous and aligned on the correct bit boundary. You get the resulting supernet in CIDR notation, its subnet mask, and a short explanation of the combined range.

Decimal ↔ Binary

With this tool you can quickly convert numbers between binary (0 and 1) and decimal (regular digits). Choose the direction in the menu and enter your number. Handy for subnet calculations, masks, or practicing binary!

Port Number → Service

Enter a port number (e.g. 80, 443, or 1521) to see which service it maps to, including the protocol (TCP/UDP).

Source: IANA.org.

DNS Tool

This DNS tool supports both forward and reverse lookups: enter an IP address to retrieve the hostname (PTR record), or enter a hostname to find its IP address (A or AAAA records). Useful for checking mail server configs, debugging DNS, or simply understanding how name resolution works.

Calculate a network address with bitwise AND

With this tool you can see, step by step, how a network address is calculated using a bitwise AND between an IPv4 address and a subnet mask. Enter an IP address and subnet mask (both in decimal notation), and the tool shows the binary representation, lines them up, and applies the AND rule bit by bit.