IP Subnet Calculator

IP Subnet – Quick Cheat Sheet

• CIDR /p → mask has p ones then zeros (e.g., /24 → 255.255.255.0).
• Total addresses = 2^(32−p). Usable (traditional) = total−2 for p ≤ 30.
• /31 = point-to-point (2 usable, no broadcast). /32 = single host address.
• Wildcard mask = bitwise NOT of subnet mask (useful in ACLs).
• Private ranges: 10/8, 172.16/12, 192.168/16. Link-local: 169.254/16. CGNAT: 100.64/10.