I have used MRTG in the past on a linux box to monitor traffic in and out of my Cisco Router

check this page for more sites. So one sent me the link some time back and I See its still up

http://dynacont.net/documentation/linux/network_monitoring/

Mike

"We must reject the idea that every time a law is broken, society is guilty rather than the law breaker.It is time to restore the American precept that each individual is accountable for his actions." ~ Ronald Regan