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You are here: Home / Networking / Firewalls & Security / What is an IP address?

What is an IP address?

February 22, 2014 By Richie 4 Comments

An IP address is a unique number assigned to your computer to enable identification over a network. You could say an IP address is like your home address where you live, and the network traffic is like your mail, and for your mail to be delivered correctly, the post office needs to know your address. A computer network operates in a similar way in that each computer on a network is assigned a unique number (your address) to enable the “packets” of data (your mail) to be delivered to the correct computer. When the packets arrive at your computer, they’re put back together again and become web pages, video and audio etc.

The two most common methods of assigning an IP address are:

  1. DHCP (Dynamic Host Control Protocol)
  2. Static IP Assignment

The first method, DHCP is automatic and widely used. With DHCP, when your computer connects to the network, it will be automatically assigned an IP number by the network host (another computer or router/modem) and after a time, will refresh that connection and get a new IP address. Now your computer (also known as a client) can send and receive data packets to/from the host over the LAN (Local Area Network), and the host can send and receive packets to/from the internet over the WAN (Wide Area Network).

The second method, static assignment, is generally only used by servers or by users who specifically request a static IP from their Internet service provider, and usually for an extra fee. With static IP assignment, IP numbers remain the same and do not change over time like DHCP addresses do. From that point on, everything works the same way as DHCP, data packets are sent and received to/from the client and host over the LAN, and to/from the host and internet over the WAN.

What does an internal IP or external IP address mean?

Confusion about networks and how they work (particularly with home networks) usually arise when we talk about the LAN, WAN, external IP address and internal IP address. So let’s try to clear things up so you can have a better understanding of how a network operates.

Diagram 1.a below is a visual representation of a typical home network and WAN (click to see a larger image/diagram).

Shows a typical home network setup with modem, LAN and WAN diagrams
Shows a typical home network setup with modem, LAN and WAN diagrams

Let’s go through each number on the diagram…

  1. This is a desktop computer (similar to what you would be using) which is a CLIENT on the home network LAN. It’s internal IP address is 192.168.0.2. This IP number is negotiated with modem/router which is the network HOST.
  2. This is a modem which may also have a built-in router, firewall, WiFi or VoIP ports but for the sake of simplicity, our example device is a basic modem with built-in router. This modem/router plays two important roles on the home network:
    1. On the LAN side it acts as the network HOST and controls assignment of IP numbers (from 192.168.0.2 to 192.168.0.254 with its own Internal IP address as 192.168.0.1 a.k.a default gateway) using the DHCP protocol.
    2. On the WAN side it acts as a CLIENT to the ISP’s HOST server and assigned an IP number by that server using the DHCP protocol (the real IP number will vary according to what ISP you are using but as an example we will use: 127.150.112.92).
  3. This is your ISP’s server which acts as a HOST to your modem/router and controls assignment of the IP number given to your modem/router using DHCP. It also verifies your modem login details and allows or disallows access to your ISP’s network.
  4. Lastly is an example web server. A web server is simply a computer that stores web pages and other data files and “serves” them up to any computer that requests it. When you requested the page you are reading now, you probably clicked on a link first, by clicking that link, your computer sent a request to your modem/router, which then sent the request to your ISP’s server, which then sent the request to our web server. Our web server then sent back this page to your ISP’s server, which then sent it to your modem/router, which finally sent it back to your computer. This transaction takes place in milliseconds.

As you can see, an internal IP address is simply an IP number on the LAN, and an external IP address is the IP number on the WAN. If a website “logs” your IP address (for instance in a forum), it will always be the WAN IP number, not the LAN.

The number system used on your LAN may differ from the above example, but the concept is the same. There are three (3) numbering systems reserved for private networks, they are:

  • 10.0.0.1 to 10.255.255.255
  • 172.16.0.1 to 172.31.255.255
  • 192.168.0.1 to 192.168.255.255

Do I need an external static IP address?

Unless you have a server running 24/7 or another specific purpose, you do not really need an external static IP address. However, if you are using file sharing software (p2p) then you may need an internal static IP address so that any ports you forward from your modem/router are attributed to it. Port forwarding and setting up static IP addresses is beyond the scope of this guide but if you would like more information please visit http://portforward.com.

If manually altering network settings is not your cup of tea, then you might find it easier to simply enable UPnP (Universal Plug And Play) in your computers network settings. Please read the ComputerHope article on UPnP which outlines UPnP along with instructions on how to enable it.

  • More information about IP Address at Wikipedia
  • Help with Microsoft Windows (official)
  • Search Google for IP Address

Filed Under: Firewalls & Security, Miscellaneous, Modems, Networking Tagged With: external IP, I.P, internal IP, Internet Protocal, IP address

Comments

  1. Ken C. Wilt says

    May 15, 2014 at 6:22 am

    Hi,
    very informative article about ip adress. What about how to find my own public (WAN) ip address ?
    What do you think about online ip finder or whatsmyipaddress? Are they reliable ? How do they work ?

    Reply
    • ComputerTech says

      May 16, 2014 at 8:05 pm

      Hi Ken,
      thanks for the feedback mate. Most IP finder type websites are good and all use the same or similar techniques to find your external WAN IP address. My own IP finder http://whatismyipaddress.ricmedia.com/ uses Apache to discover your WAN IP but some sites use PHP which is also good.

      Cheers!
      Richie

      Reply
      • dick says

        February 13, 2015 at 11:56 pm

        thanks friend but how can i get ip address of neighbour computer that exist in my neighbour WiFi network

        Reply
        • Richie Brereton says

          February 14, 2015 at 10:49 am

          Howdy, if you have physical access to the computer: just go to Control Panel > Network & Internet > Network Connections, then right click over the active wireless adapter, then choose Status menu item, then click the Details… button on the window that pops up. Look for this entry: IPv4 Address: xxx.xxx.x.x (192.168.1.10 etc) and that’s your IP address.

          If you do not have physical access to the computer but it’s on your network, just login to your modem and view connected devices to see each IP address.

          If you do not have physical access to the PC and it’s on another network, all I can give you is this link 🙂 http://arstechnica.com/security/2012/08/wireless-password-easily-cracked/

          Cheers! Richie

          Reply

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