What Is a Private IP Address?
Private IPs (10.x, 172.16.x, 192.168.x) only work inside your own network. The three RFC 1918 ranges, how NAT gets them online, and common router defaults.
What Are Private IP Addresses?
A private IP address is one reserved for use inside a local network (LAN): your home, an office, a school. Routers on the public internet drop traffic to and from these addresses, so a private IP cannot reach a server outside its own network on its own. They come from RFC 1918 (1996) and exist to save IPv4 addresses: reuse private ones inside, share a single public IP for the internet.
RFC 1918 Private Address Ranges
| Class | Range | CIDR Notation | Total Addresses | Typical Use |
|---|---|---|---|---|
| Class A | 10.0.0.0 - 10.255.255.255 | 10.0.0.0/8 | 16,777,216 | Large enterprises, data centers |
| Class B | 172.16.0.0 - 172.31.255.255 | 172.16.0.0/12 | 1,048,576 | Medium-sized organizations |
| Class C | 192.168.0.0 - 192.168.255.255 | 192.168.0.0/16 | 65,536 | Home and small office networks |
192.168.1.x and so may your neighbor's. No clash, because those addresses never appear on the public internet.
How NAT Connects Private IPs to the Internet
Your router does Network Address Translation (NAT) in between:
- Your device (say
192.168.1.10) sends a request to a website. - The router swaps the private source IP for its own public IP and notes the mapping in its NAT table.
- The website replies to the router's public IP.
- The router looks the mapping up, puts
192.168.1.10back as the destination and passes the reply on.
That is how hundreds of devices in one house share a single public address without you noticing.
Common Home Network IP Addresses
| Router Brand | Default Gateway IP | Device IP Range |
|---|---|---|
| Linksys, Asus, TP-Link | 192.168.1.1 | 192.168.1.2 - 192.168.1.254 |
| Netgear, D-Link | 192.168.0.1 | 192.168.0.2 - 192.168.0.254 |
| Apple AirPort | 10.0.1.1 | 10.0.1.2 - 10.0.1.254 |
| Xfinity / Comcast | 10.0.0.1 | 10.0.0.2 - 10.0.0.254 |
Your device gets its private IP from the router's DHCP server, which hands addresses out from a pool and tracks the leases so two devices never get the same one.
Security Benefits of Private IPs
- Not reachable from outside. Nothing behind NAT can be contacted from the internet unless you set up port forwarding.
- Hidden topology. An outsider cannot tell how many devices you have or which addresses they use.
- Smaller attack surface. Only the router's public IP is exposed.
A useful layer, not a complete one: you still need a firewall, strong passwords and updated devices. IPv6 has so many addresses that NAT is not needed and every device can have its own public address; security there comes from firewall rules and privacy extensions instead.
Try it on a real address. Free, no account needed.