Ask Leo! by Leo A. Notenboom

How is my IP address assigned?

Search First! Then browse: Categories | Full Archive | By Date | Newsletter

Home » Networking

Summary: Every device on an TCP/IP network must have a unique IP address. IP addresses are assigned, either automatically by DHCP, or by manual configuration.

Given that IP address must be unique for every computer attached to the internet,how is it possible that we do not plug in IP addresses for the computer we want to connect?

Well, every device connected to the internet must have a unique IP, it's true. And they're assigned one of two ways: static or dynamic. But there's also a useful trick that lets multiple computers share a single IP address ... and that trick is called a router.

Static IP addresses are exactly that: static or unchanging. They are assigned by your network administrator or ISP, and yes, you do have to configure the computer or other internet device manually to respond to that specific address.

But, as you point out, most folks don't need to do that. So how do they get their IP addresses?

Enter the dynamic IP address and "DHCP" or Dynamic Host Configuration Protocol.

Using DHCP (which is the default for Windows TCP/IP connections) the computer broadcasts a special request for an IP address to the network. An upstream device, commonly belonging to your ISP, responds with an IP address that the computer then configures itself to use. Especially when many computers aren't connected continuously, this allows the ISP to reuse the IP addresses of computers that have disconnected from the internet.

If you need your computer to be identifiable on the internet ... for example if you're running a web server or want people to be able to connect to your machine, you'll probably need or use a static IP address. On the other hand, if all you do is connect out to surf or read email, as most users do, then a dynamic IP address is the easiest to configure.

Routers are devices that allow multiple computers to "share" a single IP address. The device that's connected to the internet is the router, and it has a unique IP address. The router can then act as the DHCP server to the local network handing out local IP addresses to the computers connected to it. As traffic flows across the router, it does the job of translating the IP addresses from the local addresses it has assigned, to the external IP address it was assigned, and routing the right bits of data to the right computer ... hence the name.

One of the many side effects of using a router is that it can be assigned a static address on the internet, and hand out dynamic IP addresses locally, vice versa, or any combination.

Related:

Article C2328 - April 10, 2005

Helpful? Get new articles weekly by email in my FREE newsletter!

Your Name:
Your Email:


Why Subscribe?

Recent Comments
33 Comments

HI this article was really very simple to understand and was very helpful

Thanks...
Zac

Posted by: Zac at June 20, 2008 9:15 PM

Can we assign an IP address to an ARM microcontroller?

Posted by: mack nicks at September 12, 2008 4:58 AM

I have a hp pavilion desk top,I'm try to set up my quest qiuckconnect,The phone company told me I need to set my IP address to default,How do I do this?

Posted by: Bambi at September 16, 2008 9:52 PM

if only the last two number is not the same and im getting email from 2 different person from same ip for eg

ddd.DD.FF.RT
ddd.DD.FF.HG
does this mean they using one pc ??

Posted by: rgmania at September 18, 2008 2:51 PM

setting up a security system with internet connection with a router on the network. however when trying to connect from net no response. when ping the ip message destination port unknown comes up

Posted by: millard at December 10, 2008 1:13 AM

how my dhcp scope will create to my local lan while there is no scope creation for ipv6.

Posted by: shekhar at February 12, 2009 11:33 PM

good day Leo

I have a static IP at home but i cannot get througth to my pc from the my office.

can you tell me if i have to do some adjustments to my home pc.

thanks regards

Posted by: G Mylonas at March 20, 2009 4:12 AM

HOW CAN ASSIGN IP V6

Posted by: MD.NOMAAN at April 26, 2009 7:54 PM

hai,
Thanks for your information.And i know my ip address by using ip-details

Posted by: sri at June 20, 2009 5:17 AM

Hi,
Here Only i know what's the purpose of router and i want more basic network concepts like this........

Posted by: Yadeeshkumar at September 25, 2009 8:06 PM

Post a comment on "How is my IP address assigned?":






(Email Address will not be published.)

Remember Me?

By popular demand...
my tip jar
Cuppa Joe
Buy Leo a Latte!

(you may use HTML tags for style)

RSS feed Subscribe to the RSS Feed specifically for comments on this article.

Before commenting, please...

  • Read the article at the top of this page. If your comment shows you didn't, it'll be deleted and ignored.

  • Comment only on this article. Use the Google search box at the top of the page if you have a question about something else.

  • Don't include personal information in the comment. No email addresses. No phone numbers. No physical addresses.

  • Don't spam. Excessive links to unrelated sites within a comment or across multiple comments will cause all such comments to be removed.

  • Don't ask me to recover lost passwords or hacked accounts. I can't, and those comments will be deleted.

  • I can't respond to every comment. And I can't vouch for the accuracy of others who do.

Please wait. Your comment is being processed ...


Question? Ask Leo!