When he goes on-site, network detective Tony Fortunato carries about 20 tool. He pays for only one of them, a portable network analyzer. The rest are free, or have free versions. They include:
WireShark, a protocol analyzer;
MRTG (Multi-Router Traffic Grapher, used not only for monitoring and graphing SNMP devices, but graphing any caputured data;
Look@LAN, for network scanning (note that it is no longer supported);
PuTTY, a telnet client;
 —PicPick, a screen capture tool