Your computer’s IP address is its unique identifier on the network. Whether you have an internal network or you want to put a web server on the Internet, you need an IP address. IP addresses are part of the TCP/IP communication protocol. You need to understand TCP/IP to work with small and enterprise networks. But what do you do with a computer that already has an IP address? Can you change it? The answer is “Yes.”
How Does Your Computer Get an IP?
Before you change your IP, it’s best to understand how your computer gets its IP in the first place. There are two ways you can assign an IP address
- Static IP assignment: when you manually assign an IP on a computer, it never changes. This is a static IP.
- Dynamic (DHCP) assignment: Dynamic Host Control Protocol (DHCP) is the preferred way to assign an IP address.
A static IP was a part of most networks over a decade ago. A network administrator identified a range of IP addresses needed for each computer and printer and each IP was assigned to the computers one-by-one. The problem with this approach is that you need to keep track of your IP addresses manually. If a computer breaks or if an employee leaves the company, the IP is no longer used. You must manually audit and track all IP addresses as they are used and unused.
With networks growing as an integral part of an enterprise, static IP addresses are no longer viable in networks that have hundreds and thousands of computers. The other option for IP address assignment is DHCP. DHCP keeps track of any IP addresses on the network. This includes expired IP addresses, ones that are no longer used and IPs that persist on the network. You can also assign static IP address using DHCP.
DHCP servers can be physical machines on your network or routers. In small home networks, the personal router often acts as the DHCP server. These routers have router tables that are then used to route traffic to external and internal resources on the network.
Identifying Your IP Address
Before you change your IP address, you need to know the current address. In Windows, you use the ipconfig utility to find out the current IP address. This utility runs in the Windows command line. First, click the Windows Start button and type “cmd” into the text box. Press “Enter” to open the command line utility.
Type the following code into the command line:
The “all” switch displays all IP information for all network adapters. An adapter can be virtual or physical, so you might see several adapters when you type the command. Virtual adapters are items such as a VPN connection. Physical adapters are your wireless network card or the hardware network card installed on your computer.
Locate your physical network card in the list and find your IP address. This is the IP address assigned to your card. If it’s a small home network, it probably starts with “192.168.1” and the network mask is “255.255.255.0.” For larger networks, you probably have an IP starting with “10.” or “172.” Enterprise networks also have a different subnet mask depending on the amount of network segments.
Another important part of this information is the DNS server. A misconfigured or down DNS server affects your computer’s ability to connect to the Internet. You won’t be able to access websites if the DNS server doesn’t work properly.
Changing Your IP Address
The way you change your IP address is dependent on whether you have a static IP address or use DHCP. In most environments, DHCP is used. Since DHCP is automated and uses a server, you just need to refresh your IP address by releasing the IP and then recalling the DHCP server for a new address. Luckily, you don’t need to do this manually. You can use the icpconfig utility to perform a refresh.
Type the following command into the Windows command line tool:
This command refreshes the IP address. Now, if your DHCP doesn’t release the IP, you’ll keep the same IP address.
If you want to get a new IP address from your ISP, you need to refresh the IP at the router level. The easiest and best way to get a new IP from the ISP is to reboot the router. The best way to do this is to power down the router and power it back on. Be aware, though, that it means that any computers connected to the Internet from your home router will lose associated IP addresses and won’t be able to connect to websites until the router powers back on.
You can also manually assign a new IP address to your computer. This is done in your network card’s configuration in the TCP/IP settings. You’ll also need to manually assign a subnet mask along with two DNS servers. This can sometimes help with your DHCP server isn’t working properly. It’s a temporary solution until you get your router or DHCP server to start functioning again.
Each time you reboot your computer, essentially the same process happens. The IP is released and then reassigned to your computer. In DHCP environments where the IP lease is long, you will probably get the same IP address, but you can set the least time shorter to help facilitate a new IP assignment when the computer reboots on the network.
You might need to assign computers on your network with a new IP address. DHCP is the way to go even if it’s a small network, because you don’t ever need to mess with IP addresses. If you accidentally assign the same IP address to more than one device, erratic behavior occurs. For the most part, the new computer kicks the other computer off the network. For this reason, you should choose DHCP or be careful about the IP address you assign any new computers.