The SNMP event detector in NX-OS does not support a delta or incremental polling type so counter objects cannot be properly monitored. This makes it difficult to monitor things such as interface utilization. This solution repurposes the SNMP ED along with a Tcl script and a hidden VSH command to provide syslog alerting if any of a list of interfaces exceeds a configurable threshold.
First, configure an EEM applet using the SNMP ED. This applet will monitor sysUpTime and fire whenever sysUpTime is greater than 0. This will always be true. The point of this applet is to run each time the polling interval pops and execute the Tcl script.
In this example, the script will monitor the utilization of Ethernet3/1, Ethernet3/2, and Ethernet4/1 (using the "show interface" command). If any of the iterfaces' utilization is over 90%, a syslog message will be generated for that interface. That syslog will look like: