Configuring DHCP or Static IP From the Command Line

tag:blogger.com,1999:blog-7495121580708212210.post-65120493181771729422008-01-21T20:34:00.000-07:002008-01-21T20:35:04.167-07:002008-01-21T20:35:04.167-07:00Configuring DHCP or Static IP From the Command LineConfiguring DHCP or Static IP From the Command Line: netsh netsh is a pretty useful command-line tool that lets you control tons of things about your network interfaces and services. One really neat thing that netsh will do for you is to let you set IP addresses, DNS and WINS servers. It works on Windows 2000, XP and .NET Server. Suppose I have a laptop that travels between an office in Washington, DC, and an office in Los Angeles. The DC office uses DHCP. The LA office uses static IP addresses and when it’s there, the laptop is supposed to use IP address 192.168.2.10, subnet mask 255.255.255.0, WINS server 192.168.1.100, DNS server 192.168.1.100. Whenever I take the laptop to LA, I’ve got to punch in all kinds of numbers before the thing will work. When I return to DC, I’ve still got work to do, as I’ve got to open up TCP/IP properties and tell the system to stop using static addresses and instead use DHCP. netsh can help here, as I can use netsh commands in a batch file; make one batch file for DC and another for LA. First, I’ll build the DC batch file. I’ll need three commands. One tells my system to get its IP address from DHCP, the next says to get its DNS server from DHCP, and finally the third says to get its WINS server from DHCP. They look like this: netsh int ip set address local source=dhcp netsh int ip set dns local source=dhcp netsh int ip set wins local source=dhcp These are the simpler commands. I just open up Notepad, type them in, and save the file somewhere on my system’s path as dodc.cmd. "netsh int ip set" is the starting point for every one of these commands. "netsh" is the overall command, and it does lots and lots of things. But to modify the behavior of a particular network interface, I use the subcommand "int," which is short for "interface." Within that, I could do several things, but in the particular case I want to change the IP settings, hence the IP, and I want to change ("set") those settings rather than display them, so I use "set" instead of "show." By the way, netsh will always give you help if you ask it. Just type "netsh" all by itself and your prompt will change from "C:\>" or whatever to "netsh>;" you can then type "?" to find out what commands netsh will accept, one of which would be "int." If you then typed "int" then the prompt would change to "netsh interface>," and a "?" would tell you that "IP" was one option, and so on. The three commands pretty much won’t vary from one system to another unless you’ve got more than one NIC. If you’ve got more than one NIC, then you’ll want to tell netsh which NIC you’re trying to configure. In that case, replace the word "local" with the NIC’s name in quotes, as in netsh int ip set address "Local Area Connection 2" source=dhcp Next, I’ll tackle the LA batch file. I want to set the IP address to 192.168.2.10 with a subnet mask of 255.255.255.0 and a default gateway of 192.168.2.1. That command looks like this: netsh int ip set address local static 192.168.2.10 255.255.255.0 192.168.2.1 2 It starts with "netsh int ip set address local" as before, but now instead of "source=dhcp" I specify "static," meaning that it’s a static IP address. The three four-quad values following are, of course, the IP address, subnet mask, and default gateway. The "2" at the end is the metric for the default gateway. As it’s at least one hop away from anywhere in the Internet, I specified "2," but you could set it to anything that makes sense. Next, I’ll set the DNS server to 192.168.1.100. That command looks like this: netsh int ip set dns local static 192.168.1.100 primary Again, the "static" parameter says that we’re specifying a value rather than using DHCP. The IP address is of course the IP address of the DNS server, and "primary" says to do a dynamic DNS registration on the primary DNS suffix. The alternative to "primary" is "none," which says not to do any dynamic DNS registrations, or "both," which means to register on all DNS suffixes. The command to set a WINS server is similar: netsh int ip set wins local static 192.168.1.100 Just like the DNS command, except without the primary/none/both option. Collecting the commands together, we get doLA.cmd: netsh int ip set address local static 192.168.2.10 255.255.255.0 192.168.2.1 2 netsh int ip set dns local static 192.168.1.100 primary netsh int ip set wins local static 192.168.1.100 Now when I go to LA, I just open a command prompt and type DOLA. When I go to DC, DODC. Very convenient. netsh is a pretty powerful command, and I hope I’ve inspired you to look at it further! Jason Caronenoreply@blogger.com