Networking
IPv4
The standard internet addressing scheme. IPv4 addresses are 32-bit numbers written as four octets — like 192.168.1.1.
IPv4 is the fourth version of the Internet Protocol and the addressing scheme that underlies most networks today. An IPv4 address is a 32-bit number written as four decimal octets separated by dots — like 192.168.1.1.
IPv4 has been the foundation of internet networking since 1983. It defines how devices on a network are addressed and how packets are routed from source to destination.
A 32-bit address space allows for about 4.3 billion unique addresses — which sounded like more than enough in 1983, and turned out not to be. The combination of NAT (which lets millions of devices share one public IP) and private address ranges (10.x.x.x, 172.16-31.x.x, 192.168.x.x) has extended IPv4's life well beyond when the address exhaustion problem would otherwise have ended it.
IPv4 headers carry source and destination addresses, a TTL (time to live) counter that decrements at each hop to prevent packets from looping forever, protocol identifiers, and checksum data. The protocol is connectionless — it routes packets independently and doesn't guarantee delivery or order (that's TCP's job).
Despite IPv6 being over 25 years old, the vast majority of enterprise networks remain on IPv4 for internal addressing. The transition complexity, the maturity of NAT, and the cost of dual-stack infrastructure have made IPv4 remarkably durable. Most networks will run some form of IPv4 for the foreseeable future.