Address Allocation for Private Internets
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Y. Rekhter, B. Moskowitz, D. Karrenberg, G. de Groot, E. Lear · 1996-02
Abstract
RFC 1918 designates three IPv4 address ranges — 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 — as private address space for use within organizations without global internet routing. Hosts using these addresses are not directly reachable from the public internet and require Network Address Translation (NAT) for external communication.
Why This RFC Matters
RFC 1918 addressed the impending exhaustion of IPv4 addresses by formalizing a practice many organizations had already adopted informally: using non-routable address blocks internally. The three ranges it defined — particularly 192.168.x.x and 10.x.x.x — became ubiquitous in home routers, enterprise networks, and cloud VPCs worldwide. While RFC 1918 bought years of breathing room before IPv4 exhaustion, it also accelerated the deployment of NAT, which in turn introduced complexity for peer-to-peer applications, VoIP, and protocols like IPsec that embed IP addresses in their payloads. The private address ranges it defined are still in universal use today.