No. It is not mandatory to use snmp but it is extremely useful. If you just wish to see if a device is on, you can just use "ping" as your only service and your icon will be green if the Dude receives a response and red if it doesn't. If you are using the Dude to manage a device that uses RouterOS, you can use some of the built in functions to monitor a few services (memory, cpu, etc). Using snmp allows you to monitor a wide variety of different aspects of your devices. The great part is that they don't have to be made by MikroTik (I use the Dude to monitor Cisco switches and routers as well as the MikroTik devices). Using snmp, you can monitor how much data is flowing through an interface, the temperature of equipment, etc. It is just another tool to make life just a little easier for the network administrator that has a lot to manage.