IPv4 Range Expander
Given a start and end IPv4 address, this tool calculates a valid IPv4 network with its CIDR notation.
What is the IPv4 Range Expander?
The IPv4 Range Expander finds the smallest CIDR block that fully covers any given IP address range. This is useful for firewall rules, routing tables and network planning.
How Does CIDR Expansion Work?
The algorithm compares start and end IPs bit by bit to find the highest common prefix length. The result is the smallest CIDR block containing both addresses – the actual range may be larger than what you entered.
Use Cases for IP Range CIDR
Typical use cases include: summarizing IP ranges for firewall ACLs, converting geo-IP databases (which often come as ranges) into CIDR blocks, and network planning for ISPs.
Frequently Asked Questions
Answers to common questions about the IPv4 Range Expander
The IPv4 Range Expander calculates the smallest CIDR block (network) that fully contains a defined IP address range. The resulting CIDR block may encompass more addresses than the entered range.
CIDR blocks must always be aligned to powers of 2. If your IP range does not exactly match a CIDR block, the next largest block that fully contains your range will be used.
Typical applications are: creating firewall rules for IP ranges from lists, summarizing multiple subnets, converting geo-IP ranges into routable CIDR blocks, and network documentation.
When start and end address are identical, the result is a /32 block – exactly one single host address. This is the smallest possible CIDR unit and encompasses exactly one IP address.
Yes, the calculator works with all valid IPv4 addresses, including private address ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) and public addresses.