Network utilities

argus : network auditor
arpwatch : keep track of the MACs on your wire
cdpr : cisco discovery protocol reporter
cheops : snmp, network discovery and monitor tool
etherape : network monitor and visualization tool
hping: hyper ping tool
iperf : measure IP performance
ipsc : IP subnet calculator
iptraf : network monitor
mrtg : multi router traffic grapher
mtr : traceroute tool
nmap: the standard in host/port enumeration
ntop : network top, protocol analyzer
rrdtool : round robin database
tcptrack : track existing connections