How to monitor bandwidth usage of a port

From Netmon

How To Monitor the Bandwidth Usage of a Port on Your Switch or Router

You can use Netmon to see how much traffic is being sent over a port on your switch or router. Netmon will show you the current bandwidth usage, and optionally a historical graph so you can track bandwidth usage over days, weeks, or even months.

First, the switch or router must be added as an SNMP device in the Devices section of Netmon. Follow the instructions at http://wiki.netmon.ca/index.php/User_Guide:Monitoring_Devices#Adding_a_New_SNMP_Device to add the device to Netmon before continuing with this HOWTO.

Click on the Devices icon in the Netmon toolbar, then in the Devices Explorer frame on the left, expand the device, then expand Network Activity, and click on the network interface. This is illustrated below:

After clicking on the network interface, Netmon will show you a bar graph representing a real-time snapshot of bandwidth usage on that port. If you would like to enable historical tracking for this interface, check 'Enable SNMP logging'. Netmon will then begin storing the real-time snapshots.

To see a history graph of the bandwidth usage for this port, Click on the Reports icon in the Netmon toolbar, then choose the Bandwidth Activity Report.

Select the device and network interface, and the time period over which you wish to see bandwidth usage. This shows you a history graph of bandwidth usage for this port.

For more information about this topic, see http://wiki.netmon.ca/index.php/User_Guide:Monitoring_Devices#Using_the_Interface_Explorer