Hi, If you want to see how network monitoring system will capture the SNMP, then you have to follow below steps
1. Create a VM and install any trial software of NMS
2. Map that VM to the GNS application by going to preferences
3. Create the network architecture and connect devices to this VM
4. Add the management IP to network devices/VM then import the MIB in the NMS VM
5. Do the snmp settings on the switches/router