IP Range Input
Valid Start IP Required
Valid End IP Required
IP Range to CIDR Converter
Convert any starting and ending IP address range into the exact CIDR blocks required for your configuration. This tool identifies the minimum number of subnets needed to cover a specific range, providing the precise slash notation for firewalls, ACLs, and routing tables.
Slash Notation Output
Accurate Binary Mapping
Config-Ready Results
How to Use the IP Range to CIDR Converter
Why Convert IP Ranges?
Network devices like firewalls (AWS, Azure, Cisco) and routers rarely support arbitrary IP ranges (like .10 to .50). They require CIDR (Classless Inter-Domain Routing) blocks. This tool mathematically "stitches" together the largest valid blocks to cover your range exactly.
Step-by-Step Instructions
- 1Input Start IP: Enter the first IP of your range (e.g.,
192.168.0.10). - 2Input End IP: Enter the last IP of your range (e.g.,
192.168.0.50). - 3Convert: Click "Convert to CIDR" to generate the optimized list of network blocks.
Pro Tip: Multiple CIDR blocks are often required because a single block must start on a binary boundary that matches its size.
Frequently Asked Questions
Why does my range result in multiple CIDR blocks?
CIDR blocks must be powers of 2 (2, 4, 8, 16, etc.) and must start on an address divisible by that size. If your range starts at .10, we must use a /31 to reach .12, which then allows for a larger /30 block. This ensures we don't include IPs outside your specified range.
What is the benefit of using CIDR over Ranges?
CIDR notation is the universal language of the internet. Using standardized blocks improves routing efficiency and is a requirement for Cloud security groups (AWS VPCs) and modern firewall access control lists (ACLs).
Can I use these results for firewall rules?
Yes! This tool provides the exact CIDR blocks needed to permit or deny a specific range of traffic. Simply copy the results into your firewall configuration to ensure precise security without "over-permitting" the network.