I recently wanted to start monitoring some ports on my switch stack. Specifically several uplink ports and several trunk ports. Doing a little research I found the best plugin was the "check_iftraffic3" plugin available from the Nagios Plugin Exchange. Ref: http://exchange.nagios.org/directory/Plugins/Network-Connections%2C-Stats-and-Bandwidth/check_iftraffic3/details

I modified the perl script slightly to format the output a bit differently. The biggest trick to determine the interface ID. Using SNMPWALK on my Nagios server I was able to look at the various interfaces in my switching environment.

snmpwalk -v 2c -c public aaa.bbb.ccc.ddd ifTable

Configure a new check command in the standard fashion and off you go! Oh, I had tweaked the output slightly and created a PNP4NAGIOS template to better display the IN/OUT data on the same graph vs. individual graphs where the "scale" of the graph could be misleading. I'll attach that info as a TXT file.