>• ipconfig.is

Subnet calculator

A subnet calculator for IPv4 and IPv6: the network and broadcast addresses, the usable range, the netmask and wildcard mask, a range converted to CIDR blocks, the address type and the reverse DNS zone. It runs in your browser.

What it checks

• Network, broadcast and usable range
• Netmask and wildcard (ACL) mask
• IPv4 and IPv6; ranges to CIDR blocks
• Address type and reverse DNS zone

All tools

• Domain security audit: TLS certificate, chain and versions
• DNS lookup: 20 record types, A to DNAME
• DNS propagation checker: 12 public resolvers worldwide
• TLS certificate checker: Validity and days remaining
• SPF, DKIM and DMARC checker: SPF with the 10-lookup limit
• HTTP redirect checker: Every redirect hop
• Domain WHOIS lookup: Registrar and registration date
• Subnet calculator: Network, broadcast and usable range

Every tool is also a key-free API call: see the API reference.