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Issue #236: January 29, 2012

In last week’s column, I promised I’d give a lesson on how to make sure your computer is configured to get its IP address dynamically assigned. So, here goes! Pay attention, there might be a quiz at the end.

Let’s start by understanding your home network a little better. On a typical home internet connection, you will have some sort of modem that couples you to your Internet Service Provider (aka ISP or just IP). Remember that every device connected to the Internet has to have an IP address. Your modem gets assigned its IP address by your ISP. For now, don’t worry about how, just accept that it happens. Now, if you are using only one computer in your house, it will probably be connected directly to the modem, but more commonly, your Internet connection is shared among multiple computers and other network-capable devices. I named some of them last week: smart phones, Blu-Ray players with BD-Live capability (most new kinds of audiovisual equipment, for that matter), game consoles, and networked peripherals such as hard drives and printers. Each of these devices needs an IP Address too. In order to share your Internet connection, and provide the basis for a local area network, you must have a device called a Router. Routers can be either wired, wireless, or both. The latter are probably the most common, because they are the most flexible, providing both hard wired connections, and WiFi service. In a home setup such as this, it is usually the job of the router to assign IP addresses to each device. Routers generally contain something called Dynamic Host Configuration Protocol – or DHCP. DHCP’s job is to listen for devices on the network requesting an IP address, and then assign one from an available pool of addresses, usually in the range of 192.168.x.x for a home network. There are a limited number of available addresses, so another job of DHCP is to return assigned addresses to the pool of available addresses after a period of time has elapsed, or if a given address falls silent, such as when a computer is hibernating, or has been shut down.

In order for all this to work, the attached devices must be configured to request their IP address via the DHCP service. It’s possible for a device to have a single fixed IP address assigned, and not use DHCP at all. If the fixed address falls within the reserved IP address pool managed by the DHCP server, an IP address conflict will occur when the DHCP server assigns that IP address to another device. The way to minimize the chance of that happening is to make sure all devices are configured to use DHCP. On peripherals, game systems, and the like, it’s almost a given that they will default to using DHCP. On your computer, it’s a little more complicated, which finally brings us to the lesson I promised last week.

The manner to get into the configuration varies by Windows version, so this may require you to make a few assumptions, but don’t worry – I won’t tell you to do anything that can hurt your computer. First, open the Control Panel and run the link that says either “Network and Sharing” or “Network and Internet” or “Network Connections”. If you don’t see a list of your network connections, look for a link that says “Manage Connections” or “Change adapter settings”. Locate the active connection, which will be named something like “Local Area Connection” or “Wireless Network Connection” depending on how you’re connected. Right-click it and select “Properties”. Under “This connection uses the following items:” select “Internet Protocol” or “TCP/IP” (it might say “Version 4” or “IPv4”) and again select “Properties”. This is it! Make sure the button that says “Obtain an IP address automatically” is selected. Then click on “Advanced” and go to the “WINS” tab. Make sure the “Default:” button is selected. Then, “OK” your way back out of all the dialogs. If you made any changes to the configuration, you might have to restart your computer. If all your computers are set up to use DHCP, and you are still getting IP address conflicts, there may be something amiss in your router configuration. In this case, you should contact your router’s manufacturer for more assistance.

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