The process of acquiring a dynamic address is called DHCP (Dynamic Host Configuration Protocol). This means that the ISP has a device that hands out an address to your computer when you connect to the ISP's network. This address may change from time to time, but your computer does not care what address it has, as long as it has a valid one for communication. You can learn more about how DHCP works at www.ask-leo.com
Okay, so now lets see how we can tell if your computer is getting an address. Windows users need to Click Start, then Run. When the run dialog box appears, type "cmd" (no quotes) and hit the enter key. In the black command window that appears, type (no quotes) "ipconfig" and hit the enter key.
You should get a listing of info that looks like this:
Windows IP ConfigurationLets look at what this is telling us...
Ethernet adapter local area connection:
Description . . . . . . . . . . . : Broadcom 570x Gigabit Integrated Controller
Physical address . . . . . . . . .: 0F-0F-1F-CB-99-87
DHCP enabled. . . . . . . . . . . : Yes
IP address. . . . . . . . . . . . : 192.168.1.3
Subnet mask . . . . . . . . . . . : 255.255.255.0
Default gateway . . . . . . . . . : 192.168.1.1
DNS servers . . . . . . . . . . . : 126.96.36.199
DHCP enabled means that the computer is configured to request an IP address. The next line shows the IP address that was assigned to the computer. You can ignore the subnet mask.
The Default Gateway is important. It tells you the next "hop" to the Internet. If you have a router between your computer and the ISP, then your router is your Default Gateway, and the value listed here will be your router's IP address.
The DNS server shows the address of the computer that helps convert computer names into IP addresses so they can be located. You need one or more of these entries in order to go to websites by name, such as www.google.com. You can learn more about DNS at www.howstuffworks.com
Looking for Errors
If the "ipconfig" output shows:
Media status . . . . . . . . . : Media disconnectedIt means that the computer is not plugged into the network (or the wireless card is not connecting to the Wireless Access Point). Correct this before trying to go any further.
If the IP address starts with "169.254" this means that the computer did not get a response back from its DHCP request, so the computer made up its own IP address. This IP address is worthless, and will not allow you to connect to the Internet.
How to Force Windows to Renew the Computer's IP Address
The ipconfig command has a couple of parameters that can be added to do additional tasks.
- ipconfig /all (shows a lot of additional info about your IP connection)
- ipconfig /release (drops your IP address)
- ipconfig /renew (requests a new IP address)