Monday, April 16, 2007

What is my ip address? And why would I care?

Some of you may know what an IP address is, and some may not have any idea... or care. But after enough friends have asked me about it, I figured it's time to write something up on the subject. It stands for Internet Protocol address, and if you prefer to read the wiki article, go for it...

Before I explain it, I'll offer some reasons as why you would want to know about it.
-Do you ever wish you could get to your home computer's desktop when you are not at home?
-Do you ever wish you could get to some files on your computer at home?
-Do you want to setup your own web-server, file-server, internet-radio station, email-server or game-server?
-Have you ever tried to do something like play a video-game, send a file over instant messenger, or used a p2p file sharing application and have gotten an error message saying your firewall has blocked you?

My way of explaining it to people best is, it is like your 'phone-number' for your computer using the internet. Although you may rarely care which number you are 'called or make calls with' , behind the scenes your ISP is using it to let you use their services... It is pretty easy to figure out your external IP address on the internet, is one of my quick ways to identify it. If you hooked your computer directly up to the Cable/DSL modem this would truly be your IP.

Now for the tricky part, home routers, wireless access points, and hardware firewalls.... Your home access point is the device that is directly connected to your Cable/DSL modem and it gets your external IP assigned to it. Every computer/laptop that connects to your access point gets a different 'phone number extension'.. To make things confusing, this extension is usually an internal IP address... but the good news is they are in a range specifically designed for home/private use, 192.168.x.x being the most popular range for home use..

So great, my router has an external IP address, for example: it also has an internal IP address, for example, and my computer plugged into my wireless router has an IP address too, given to me by my router.

Ok I get it.
What about Port Forwarding? What if my external IP address from my ISP changes? What if my internal IP address from my wireless router changes?


g michael amante said...

Port forwarding...

an extension to a computers IP number is a port number... for example, most webpages you view are actually running on a port, port 80. So will work just like

Sometimes, you want to forward on requests to a certain port to one of the computers behind your firewall/router. For example, if you wanted to connect to your home computer using Remote Desktop, it uses port 3389 by default(you can change it) You would go into your routers configuration settings, and forward on requests to port 3389 to the internal IP address that you want to connect to... using my example above, requests to can be forwarded on to the internal IP address of a computer running Windows XP Professional or Terminal Services (, port 3389)
get it? The only other catch is sometimes you have an additional software firewall installed and you need to enable that to allow requests to come in too on this port.

WARNING: opening up ports on your firewall does make you more vulnerable to hackers, so make sure your passwords are secure and changed often.

g michael amante said...

external IP address may change...

Most people get a Dynamic IP from their ISP by default, a static(non-changing) IP may be a possibility for a few more bucks per month, but what I like to do is use a free service from

This service lets you pick a Name, which corresponds to your IP address. The catch is you need to install a program/service, which updates the record in their system every time your IP does change. Very handy though, especially if you want the advantages of a static IP without shelling out the extra bucks...