If you have tons of money, buy Visio. Visio is very easy to use, has tons of symbols… well, you know. This article, though, will introduce you to a number of tools that will allow you to create PDF network diagrams with free, open source software on a Windows workstation.
The first tool you will need is Cygwin. The newer versions of Cygwin come with XFree86, so it is very easy to install X now. You will also want to get a nicer window manager than twm. We like to use Ice Window Manager for Cygwin. See our article on getting xterm for Windows for more tips. Finally, you will need to get a copy of XFig. There is a Cygwin port of XFig here.
To place an object in XFig like you do in Visio, you need to use Libraries. Here is the manual page on Libraries. Just select the object and drag it to your drawing. To get the dimensions correct for exporting your finished diagram to PDF format, select file/print/fit to page. Then, select file/export, and choose PDF to export the file.
Here is an example of a simple PDF network diagram created with the above method. If you would like some more sophisticated linking methods for your network topologies, check out Topology Drawer.
Of course, if you are using a *NIX system, all of the above tools will work as well, and much faster, since you don’t have to use Cygwin; however, PCs are so fast these days that the performance difference isn’t that noticeable. The price is certainly right. 🙂
[Ed. Note: Check out this detailed and updated document on installing XFig on Cygwin.]