No one is happy when the local network goes down. With a few helpful tools, however, you can start searching immediately for the nasty LAN-breaking culprit and fix the situation in an instant with a bit of skill and some know-how. Using a combination of iptraf, ifstat, tcpstat, bmon, and pktstat, you can quickly find what's impeding your data traffic through NetHogs [1] and Atop [2].

Although real-time analysis tools are good for answering questions about the current state of things on the Linux system, they are less suitable for longer-term evaluation. Answers to questions like "How much traffic did clients and network services produce in the last week" or "Who clogged things up last night at 2 o'clock?" require that you keep the data throughput and statistics constantly in sight.

Programs such as vnStat [3], ntop [4], darkstat [5], and BandwidthD [6] can help you in this endeavor as well as in drilling down into the protocols and processes. Some of the tools also provide a web-based interface and are thus ideally suited for installation on routers or servers, allowing for reliable reporting over time intervals.

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