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Private IP Address Ranges (RFC 1918) Explained

That address starting with 192.168 on your router — here's why it's always in that range.

Why private IP addresses exist

Public IPv4 addresses are a limited resource — there are only about 4.3 billion possible addresses, nowhere near enough for every device on Earth. RFC 1918 sets aside blocks of addresses that are never routed on the public internet and are reused, in isolation, inside millions of separate private networks. Your router uses NAT (Network Address Translation) to hide all of your home devices behind a single public IP address.

The 10.0.0.0/8 range

Running from 10.0.0.0 to 10.255.255.255, this is the largest private block, with about 16.7 million addresses. It's mainly used by large enterprises, data centers, and internet service providers for sizeable internal networks — you'll rarely see it as a home router default, but it comes up often in corporate VPNs.

The 172.16.0.0/12 range

Spanning 172.16.0.0 to 172.31.255.255, this block provides roughly 1.05 million addresses and is a common choice for mid-sized company networks. It's also familiar to developers: Docker's default bridge network typically uses a slice of this range, such as 172.17.0.0/16.

The 192.168.0.0/16 range

Covering 192.168.0.0 to 192.168.255.255, this is the range home routers almost always default to. If you've ever opened a router's admin page at an address like 192.168.0.1 or 192.168.1.1, this is the block you were in — sized just right for homes and small offices.

Other special ranges worth knowing

127.0.0.0/8 is the loopback range, used by a device to talk to itself (127.0.0.1, aka localhost) and never leaves the machine. 169.254.0.0/16 is the link-local range an operating system assigns automatically when it can't reach a DHCP server (APIPA) — seeing an address in this range usually signals a connection problem. Separately, 100.64.0.0/10 is a shared address space (not part of RFC 1918) commonly used by ISPs for carrier-grade NAT (CGNAT), which pools many subscribers behind one public IP.

A real-world situation worth knowing about

Because private IP addresses are only meaningful within their own network, two completely separate networks can use the same range (say, both using 192.168.0.0/24) without any issue — until you connect them. Working remotely over a VPN that bridges your home network and your office network can cause a range conflict, where it's unclear which 192.168.0.10 is meant, breaking connectivity. Changing one side's internal range to a different private block, like 172.16.0.0/12, usually resolves it.

How NAT makes private addresses work on the internet

Private IP addresses can't be routed across the public internet on their own — routers along the way would have no idea which of the millions of networks using 192.168.1.10 you meant. Network Address Translation (NAT) solves this by rewriting the source address of outgoing traffic to your router's single public IP address, then tracking which internal device each response belongs to. This is also why a device outside your network normally can't just start a connection to a device inside it — traffic has to be initiated from the inside, or explicitly forwarded through a router setting.

Spotting a private address at a glance

If an address starts with 192.168, 10., or falls between 172.16 and 172.31, it's private and only valid on that specific local network — useful to recognize instantly when troubleshooting, reading a router's device list, or reviewing logs. Any other address is very likely a public, internet-routable one, though a handful of other reserved ranges (like loopback and link-local) exist for special purposes rather than general-purpose networking.

Frequently Asked Questions

Can a private IP address connect directly to the internet?

No — private IP ranges are deliberately excluded from internet routing, so a device with only a private address can't reach the internet on its own. A router performs NAT to translate the private address to a public one, which is what actually makes the connection possible.

Why are there three separate private ranges instead of just one?

Having ranges of different sizes lets a network choose one that fits its scale. A large enterprise or ISP with huge numbers of devices might use the vast 10.0.0.0/8 range, while a home network with a handful of devices is comfortably served by the much smaller 192.168.0.0/16.