IPv4 Addressing Basics

Every machine that is on a IPv4 TCP/IP network ( a local network, or the Internet ) has a unique Internet Protocol ( IP ) address. Generally, each computer is assigned a private IP address that is visible only to the local area network (LAN). A local area network is a group of computers on the same subnet or group of computers and devices with similar addresses. Local IP addresses will be in the range of 10.0.0.0 to 10.255.255.255 or 172.16.0.0 to 172.31.255.255 or 192.168.0.0 to 192.168.255.255.

To find out what your private or LAN IP is, you can issue the IPCONFIG command from a command prompt. Simply open a command prompt and type IPCONFIG.

Each LAN (or individual computer if it's the only one in your facility) is connected to the public internet by a router. You will have one or more public IP addresses assigned to this router which connects your network to the internet for browsing websites, sending and receiving email and other tasks. This internet router (or it can be another device on your network) provide network address translation (if you are using private IP addresses) which maps your public address to your private addresses. This translation is necessary for two important reasons. Primarily for security and secondly so that each individual device does not require a public address.

Public IP addresses can be assigned statically (you keep the same address) or dynamically (the address changes periodically).

To find out what your public IP address is, use a web service. You can use the bitMASTERS tool for determining your public address by clicking here or use a service such as IP-LOOKUP.