Very useful tool and a must if you are setting up snmp checks. I'd say 50% of my checks are snmp. You see, it's not really good enough to know a switch or router pings. What you really want to find out is, "is the port operational". When you have multiple paths to a switch, it may ping, but how are you getting there? The switch may be using spanning tree to block one path, and if that path dies, the other is used. So you can be alerted to a problem, before anyone even knows that there is one. Another example is routers, DS3 units, etc that have more than one power supply, fans, etc. You can wait till both pwer supplies fail, or you can setup nagios to check the status of each, and alert you of trouble. You choose. These types of checks have prevented many failures from going unnoticed on our network.