Troubleshooting Network Problems

Inevitably, sooner or later, something will go wrong on your network. In most cases you can troubleshoot the problem using standard resources such as the error message and syslog logs.There will be those rare times, however, where the standard information sources just aren't giving you enough information to really know what is going on. In those cases, a network sniffer may be your only option. A sniffer will basically look at all the traffic at the network layer in its raw form and collect it.This means you can see the data the way your network card sees it, which is very different from how the final product looks to the application. Different sniffers provide varying levels of sophistication and features.

The primary difference between a commercial sniffer and a free one will be in remote management and in some cases advanced analysis options. In many cases the sniffer will require special drivers to be installed in order to sniff traffic.The sniffer's role is mostly to simply display the data it collects. It is up to the human user to interpret the data and determine what it means in the big picture. For this reason, the analysis of sniffer output (often called traces) is typically reserved for experienced networking experts.With a little basic information, however, a sniffer can often provide a quick look into the otherwise unseen background of network communications.We will explain the installation and basic use of GUI sniffers and a couple command-line sniffers as well.