SNMP stands for Simple Network Management Protocol
Version 1 – First version. Easy to set up. Everything in plain-text which means an attacker can intercept the strings when being transmitted.
Version 2 – Similar to version 1. Adds support for 64-bit counters. Most devices support SNMP V2 automatically as version 1 is no longer recommended due to its lack of security.
Version 3 – Adds security to the 64-bit counters. Encryption and Authentication are added and these can be used either separately or together. Setup is more complex.