I use a program called PRTG, which is a Windows/GUI version of MRTG. I monitor my switch which is a Cisco Catalyst 3550. I have set up a monitor port to mirror my uplink to my ISP. I have a STS-3 (OC-3) that connects me to my ISP. PRTG shows that I flow 50+ Mb/s to them. Network Probe 2.1 only ever show 18Mb/s or lower. What's up with the 30+ Mb/s discrepancies. Any and all help would be appreciated.