About SNMP versions
Many versions of SNMP are available.
The versions of SNMP protocol are as follows:
SNMPv1
The SNMPv1 version is the first version of the protocol and is defined by RFC 1157. This document replaces the earlier versions that were published as RFC 1067 and RFC 1098. Security is based on community strings.
SNMPv2
It was created as an update of SNMPv1 adding several features. The key enhancements to SNMPv2 are focused on the SMI, manager-to-manager capability, and protocol operations.
SNMPv2c combines the Community-based approach of SNMPv1 with the protocol operation of SNMPv2 and omits all SNMPv2 security features.
The original SNMPv2 (SNMPv2p)
Community-based SNMPv2 (SNMPv2c)
User-based SNMPv2 (SNMPv2u)
SNMPv2 star (SNMPv2*).
SNMPv3
This version of the protocol is a combination of user-based security and the protocol operations and data types from SNMPv2p, and support for proxies. The security is based on that found in SNMPv2u and SNMPv2*. RFC 1905, RFC 1906, RFC 2261, RFC 2262, RFC 2263, RFC 2264, and RFC 2265 define this protocol.