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About this tool
Given an address and a prefix length, work out the network address, broadcast address, netmask, wildcard mask and usable host range, along with the total and usable host counts.Questions
- Why is the usable host count two less than the total?
- For ordinary IPv4 subnets, the first address is reserved as the network address and the last as broadcast, so the tool subtracts two. Watch out: this tool reports
0usable hosts for/31and/32. That count is not a full explanation of those special cases:/31can be used for a point-to-point link, and/32names a single address. Check your network’s rules before treating the count as a deployment decision. - Can it plan a VLSM layout?
- Not directly. Use it to check one block at a time, or the range expander to see which CIDR blocks cover an arbitrary range exactly.