Formula: IPv4 (32-bit) ↔ IPv6 (128-bit) | CIDR: IP/prefix → network range
IPv4 uses 32-bit addresses (e.g., 192.168.1.1) supporting ~4.3 billion addresses. IPv6 uses 128-bit addresses (e.g., 2001:0db8::1) for virtually unlimited addresses. IPv4 addresses can be mapped to IPv6 using the ::ffff: prefix. CIDR (Classless Inter-Domain Routing) notation like /24 defines subnet size — a /24 subnet has 256 addresses (254 usable hosts), while a /16 has 65,536 addresses.