Public vs private IP addresses
Ask your laptop for its IP address and it will say something like 192.168.1.34. Ask a website and it will report something completely different. Both are correct — they are answering about two different networks.
Private addresses
Three IPv4 ranges are reserved for use inside local networks and are never routed on the public internet:
| Range | Size | Typical use |
|---|---|---|
10.0.0.0 – 10.255.255.255 | 16.7 million | Large corporate networks |
172.16.0.0 – 172.31.255.255 | 1 million | Medium networks |
192.168.0.0 – 192.168.255.255 | 65,536 | Home routers |
Because they are never routed, the same address can exist in millions of homes at once with no conflict. 192.168.1.1 is your router; it is also several million other people’s routers.
The public address
Your provider gives your router one public address. Everything in the house — phones, laptops, consoles, doorbell — shares it through Network Address Translation. The router keeps a table of which internal device is waiting on which reply, rewrites addresses on the way through, and delivers each response to the right place.
From outside, your entire household is one address. That is why the home page shows one value however many devices you own.
Which one you need
- Configuring your router or a printer — the private address.
- Letting a friend into a game server, or configuring remote access — the public one.
- Checking what a website sees, or whether a VPN is working — the public one.
- Diagnosing a device that cannot reach the internet — start with the private one.
The other reserved ranges
Two more will come up occasionally. 127.0.0.0/8 is loopback: 127.0.0.1 is always the machine you are sitting at. 169.254.0.0/16 is link-local, which a device assigns itself when it cannot reach a DHCP server — seeing one usually means the router is not answering.
Frequently asked questions
Which address do websites see?
The public one — your router's. Your private address never leaves your network and would be meaningless outside it, since millions of homes use the identical range.
Why does my computer say 192.168.1.34?
That is its private address on your own network, handed out by your router. Only devices in your home can reach it.
Can someone attack my private IP address from the internet?
Not directly. There is no route to it from outside. Risk arrives through something you connect out to, or through a port your router has been configured to forward inward.
Do I have two IP addresses?
At least two: a private one on your local network and the public one your router holds. With IPv6 you may also have several globally routable addresses at once.