Finding your IP Address in Mac OS X is simple. Just like on the previous page where we discussed application preferences, the entire system in general has preferences too. This can be found under the Apple Menu. Go to the Apple Menu > System Preferences > Network.
There you will see a list of your network interfaces and their associated configurations. Displayed on the right is the Network control panel of a Leopard system (10.5). Tiger (10.4) will look a little different but the basics are exactly the same. Not only can you view your IP information here, but you can also modify all configurations from here. Within this window, on top, notice the drop down menu called “Location”. By default, it is set to automatic and an automatic configuration will work in most cases. This will set the system to use whichever interface detects a connection, will set it to acquire an address via DHCP and will use the fastest connection possible. Therefore, often, Built-In Ethernet is used over AirPort if both are available.
Often, DNS Servers are not displayed if DHCP is used. To acquire your DNS addresses, you may have to go into the administration pages of your router. This is important to know how to do because your PUBLIC IP Address is different than your PRIVATE IP Address. The IP Address displayed in System Preferences will always show your PRIVATE IP Address if your computer is hooked up to a router. Otherwise, it will simply pass the Public IP Address to this Network Pane.
Knowing how to get into your router to make necessary network adjustments is key for setting up any network. However, the means to do this varies depending on the manufacturer of the router.
On the Windows side of things, you might be familiar with the command “ipconfig /all” which displays all of your network information. This will give you your DNS addresses. If you go into “Terminal” on the Mac, you are now at a command prompt. By typing in “cat /etc/resolv.conf” and enter, terminal will respond with your DNS settings. The application Terminal is located in your Applications > Utilities folder.
What is your PUBLIC IP Address?
Your public IP address is significantly different than your private IP Address. A private address is give to your computer by YOUR router. However, since your router (and network) is connected to a larger network (ie, the internet), your router receives its IP address from your ISP (Internet Service Provider). That is a public address. To find out what your public IP address is, simply go to the following link: www.whatismyip.com
This is probably the easiest way to determine what your public IP address is. Basically, just like you can enter the IP address of a computer that is on your network and gain access to the machine (for file sharing, FTP, screen sharing, etc.), entering the public IP address will get you to someone's router (or entire network). This is why it is very important to configure your router appropriately so that not just anyone can gain access to your network or personal computers.