Network Mapping at a Glance
Doing it visually with your own Perl script.

by Kent Cearley

While graphical network monitoring can be a useful management tool for system administrators, the cost of commercial solutions is often prohibitive. As the project shown below demonstrates, though, it's possible to build your own inexpensive visual map to monitor the state of your network by implementing a few Perl scripts and a little artistic creativity.

Even if you stick with a bare-bones approach, the program you'll end up with will be a useful utility for your help desk, administrators, and management to check the network status at a glance. In this project, which we'll call WebView, you'll create a map of your network with nodes colored green or red, indicating whether they respond to the "ping" diagnostic utility. A ping is an ICMP message used in TCP/IP networks to see if a remote host is alive, so a node that's pingable is one that's up and running.

The Network Map

You'll need either a paint program or an illustration software package to create an image for your network map. Figure 1 illustrates a simple layout of a small network. The sample network map drawn here is rather simplistic, but it could be as elaborate as your talents allow. This network contains Novell file servers, voice-response systems, Oracle servers, and an Internet router (the diamond) for WAN connection across T1 links.

Note that each node in the network map is filled with a uniform color and bounded on all sides by an outline of a different color. These requirements are necessary because you'll be using graphics tools to dynamically "fill" each node's region with a color to indicate its status. If the region is unbounded, the color will end up flooding your whole map. Avoid adding additional colors inside each node, or else when the filling color is poured in, only a portion will change, instead of the whole icon. But don't hold back on the creative front; you could embellish upon the geometric shapes for network devices and topologies generally seen with standard commercial products, by adding dragons and moats, spires for servers, drawbridges for routers, or a large glass house on a hill for a mainframe.

After you create your masterpiece, you'll need to export it as a GIF file. If your graphics software doesn't support GIF, you can use one of the many commercial or shareware file-conversion utilities to change the format. Once you've sketched your network map to your satisfaction and saved it in GIF format, you're ready to begin mapping the nodes to their representative graphics.

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