Next Available IP Finder
Enter your subnet CIDR and used IP addresses to find the next available IP address.
What is Next Available IP Finding?
Next Available IP Finding is an essential tool for network administrators and home-labbers who need to quickly identify free IP addresses in their subnets. Instead of manually tracking IP assignments in spreadsheets or running CLI loops, Our Next Available IP Finder makes it easy to enter a list of IPv4 addresses and instantly find the smallest possible subnet (in CIDR notation) that covers them all. You’ll also see a detailed binary breakdown, subnet mask, IP range, and a visual explanation of how the summarization works. Whether you’re a network engineer, student, or IT professional, this tool helps you optimize your network and understand route summarization in a clear, interactive way.
How Does Next Available IP Finding Work?
IP route summarization is the process of finding the smallest network (in CIDR notation) that can cover a set of IP addresses. This is useful for reducing the size of routing tables and making networks easier to manage. Here’s how the calculation is done, step by step:
- Convert each IP address to binary. This makes it easy to compare the addresses bit by bit.
- Find the longest common prefix. Compare the binary forms of all IPs and count how many starting bits are the same. This is your network prefix length.
- Determine the summarized network address. Take the common prefix and fill the remaining bits with zeros. This gives you the network address in binary, which you convert back to decimal.
- Express the result in CIDR notation. The summarized route is written as
network/prefix(e.g., 192.168.0.0/22). - Calculate the subnet mask and range. The prefix length tells you the subnet mask and the range of IPs covered by the summary.
This tool automates all these steps and even shows you the binary comparison, so you can see exactly how the summarization is determined!