Monitor Linux routers and firewalls with MRTG
MRTG, or Multi Router Traffic Grapher, is a popular monitoring and statistics tool for use on Linux platforms. It was designed to monitor the traffic load on network links, but it's highly extensible and configurable. Not only can you watch interfaces on routers and switches, but you can also analyze Linux system variables. Although this is usually done with the Simple Network Management Protocol (SNMP), MRTG also supports the use of local scripts to feed it data. The data is then converted into HTML with graphs in PNG format for a visual representation of your network.
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