Private IP Address Ranges Explained

Your laptop thinks its address is 192.168.1.100. So does mine. So do millions of others. We're all using the same address, and somehow the Internet doesn't collapse into chaos.

This isn't a bug—it's one of networking's most consequential design decisions.

The Invention of Reusable Addresses

In 1996, the Internet's architects saw a problem coming. IPv4 had 4.3 billion addresses—a number that seemed vast until you imagined every device on Earth needing one. RFC 1918 introduced something radical: IP addresses that could be reused infinitely across different networks without conflict.

Three ranges were set aside as private—addresses that would never route on the public Internet. The insight was profound: if an address can't leave its local network, it doesn't need to be globally unique. Every home, every office, every coffee shop could independently use 192.168.1.1 because those addresses would never meet.

It's like every apartment building having its own Apartment 101. The apartment number only needs to be unique within the building. The street address handles uniqueness at the city level.

The Three Ranges

10.0.0.0/8 — 16.7 million addresses

Your enterprise network when you're planning to conquer the world. Large companies use this range because they can carve it into thousands of subnets without ever worrying about running out. Different offices, departments, VLANs—the address space is so vast it becomes invisible as a constraint.

172.16.0.0/12 — 1 million addresses

The middle child that found its calling in the cloud. AWS defaults to 172.31.0.0/16 for new VPCs, landing squarely in this range. It's large enough for serious infrastructure but different enough from home networks to avoid VPN routing conflicts—a combination that made it the natural choice for cloud providers.

192.168.0.0/16 — 65,536 addresses

The range you actually see in real life. Every home router ships with this as default—usually 192.168.1.1 or 192.168.0.1. For networks with dozens or even hundreds of devices, it's more than sufficient. It's the range that brought networking to the masses.

Why Private Addresses Matter

The architects of RFC 1918 were right to worry. By 2011, IANA allocated the last blocks of IPv4 addresses. Today, every publicly routable address is claimed. But we've connected tens of billions of devices anyway.

Private addresses made this possible through multiplication. Instead of every device needing a unique global address, entire networks share a single public IP. Your home might have fifty devices—phones, laptops, smart lights, thermostats—all hiding behind one public address your ISP assigned to your router.

The same 192.168.1.x addresses appear in millions of homes simultaneously. No coordination needed, no registry to update, no permissions to request.

But there's a second benefit that matters just as much: isolation. Private addresses create a natural security boundary. Devices on the public Internet can't directly reach 192.168.1.100 even if they wanted to—routers are configured to drop that traffic. Your internal network is invisible from the outside by design.

How NAT Makes It Work

Network Address Translation allows devices with private IPs to access the Internet. The mechanism is surprisingly straightforward.

Your laptop at 192.168.1.100 sends a request to visit a website. The request hits your router, which has two faces: a private address (192.168.1.1) facing your network, and a public address facing the Internet.

As the packet passes through, the router rewrites the source address from your private IP to its public IP. It keeps a connection table noting which internal device made which request and on which port.

When the response arrives from the website, it's addressed to the router's public IP. The router checks its table, sees this packet belongs to your laptop, translates the destination back to 192.168.1.100, and forwards it to you.

From the website's perspective, it's having a conversation with your router. It never knows your laptop exists. From your laptop's perspective, it's talking directly to the website. The translation is completely transparent.

This is why fifty devices in your home can all access the Internet through one public IP. The router tracks every conversation, rewriting addresses on the fly in both directions.

Choosing Your Range

The decision is simpler than it appears.

Home networks (fewer than 100 devices): Use 192.168.1.x and don't think about it. It's what your router expects, what your devices expect, what every tutorial assumes. Pick a different third octet (192.168.2.x, 192.168.50.x) if you want to feel unique, but the default works fine.

Medium businesses (100-1000 devices): Consider 172.16.x.x, especially if employees work remotely. Using a different range than typical home networks prevents VPN routing conflicts. When someone connects from home to the office network, having distinct address spaces means their computer can tell which printer at 10.1.1.50 you mean—home or office.

Large enterprises or ambitious growth plans: Start with 10.x.x.x. The address space is so large you can subnet freely without ever worrying about exhaustion. Different offices, departments, network zones—carve it however you need. You'll never have to renumber because you planned too small.

The VPN routing trap: If your home network uses 192.168.1.x and you VPN to an office network using 192.168.1.x, your routing table becomes ambiguous. Is 192.168.1.10 the printer next to you or the server across the country? Your computer can't tell. This is why enterprises often use 10.x.x.x—it's guaranteed to not conflict with home networks.

Sources