Essential System Administration, 3rd Edition

Monitoring the Network

For most of us, networking-related tasks make up a large fraction of our system administration duties. Installing and configuring a network can be a daunting task, especially if you’re starting from scratch. However, monitoring and managing the network on an ongoing basis can be no less daunting, especially for very large networks. Fortunately, there are a variety of tools to help with this job, ranging from simple single-host network status utilities to complex network monitoring and management packages. In this section, we’ll take a look at representative examples of each type, thereby enabling you to select the approach and software that is appropriate for your site.

Standard Networking Utilities

We’ll begin with the standard Unix commands designed for various network monitoring and troubleshooting tasks on the local system. Each command provides a specific type of network information and allows you to probe and monitor various aspects of network functionality. (We’ve already considered three such tools: ping and arp in Section 5.3 and nslookup in Section 8.1.5.2 earlier in this chapter).

The netstat command is the most general of these tools. It is used to monitor a system’s TCP/IP network activity. It can provide some basic data about how much and what kind of network activity is currently going on, and also summary information for the recent past.

Tip

The specific output of the netstat command varies somewhat from system to system, although the basic information ...