If I am concerned about my "Ethernet0/1" which has index 3. I am polling every 60 seconds on a 10M Bit/S Ethernet link. 10% means 60 * (0.1 * 10,000,000)/8 = 7,500,000 in terms of ifInOctets over a 60 seconds interval, then I will configure the alarms as below:
config t snmp-server community public ro snmp-server enable traps snmp snmp-server host 172.17.194.38 public (this is to tell where is my trapd listener which is my HP OV box) rmon event 1 log trap public description "Ethernet utlization is more than 10%" owner eugene rmon event 2 log trap public description "Ethernet utlization is below 5%" owner eugene rmon alarm 1 ifEntry.10.3 60 delta rising-threshold 7500000 1 falling-threshold 3750000 2 owner eugene
If you also want to monitor ifOutOctets, then add this line in the config:
The cisco.com ftp site should be accessible using your cisco.com login credentials. Some services, such as access to published MIBs, are free to all registered users.
The commands Thomas posted are for the IOS device.
Besides making the device send traps (and needing to have your management system display or otherwise take action), you can alternatively just setup LMS (assuming version 4.1) to monitor the device and make the threshold what you desire. (Pre-LMS 4.x versions require the optional HUIM component to be licensed.) See the "Monitor Performance" section in this document for a quick start guide or the LMS documentation for more details. (Specifically Chapter 4 of Monitoring and Troubleshooting guide.)