Find a router's private IP address by entering "ipconfig" into the Command Prompt of Windows and looking at the Default Gateway address. If running Linux or Mac OS X, find the router's address by using the ifconfig application from the Terminal. Linux names this address "eth0," while Mac OS X shows "inet." In addition to local IP addresses, the Internet assigns each connected network a public IP address. Several websites, such as WhatIsMyIP.com, display this public address for visitors.
Routers assign private IP addresses to each device on the network, including computers and printers, and locate and forward data to and from each device. Knowing the various private and public IP addresses of a network is vital for diagnostics, gaming, server management and connecting to local and remote devices.
Networks use two different versions of IP addresses: IPv4 and IPv6. IPv4 uses four sets of three-digit numbers, with each set going as high as 255. IPv4 is running out of numbers to use for each Internet network, and IPv6 provides a vast number of additional addresses by using eight sets of four-digit hexadecimal numbers. Unlike IPv4, IPv6 allows each device on a local network to have a public Internet IP address.