For internal purposes I had to monitor some snmp facts of a sonicwall.
Here’s the OID list
Sonicwall CPU usage as percent .1.3.6.1.4.1.8741.1.3.1.3.0 Sonicwall Memory usage as percent .1.3.6.1.4.1.8741.1.3.1.4.0 Sonicwall Maximum Connections .1.3.6.1.4.1.8741.1.3.1.1.0 Sonicwall Current Connections .1.3.6.1.4.1.8741.1.3.1.2.0 Sonicwall Firmware version: .1.3.6.1.4.1.8741.2.1.1.3.0 Sonicwall Serial: .1.3.6.1.4.1.8741.2.1.1.2.0 Sonicwall ROM: .1.3.6.1.4.1.8741.2.1.1.4.0 Sonicwall System Description: .1.3.6.1.2.1.1.1.0
Luck may vary (there are many different type of (Dell) Sonicwall appliances)
Hope this helps you.