SNMP Versions
Cisco IOS software supports the following versions of SNMP:
*SNMPv1 - The Simple Network Management Protocol: A Full Internet Standard, defined in RFC 1157. (RFC 1157 replaces the earlier versions that were published as RFC 1067 and RFC 1098.) Security is based on community strings.
*SNMPv2c - The community-string based Administrative Framework for SNMPv2.
SNMPv2c (the "c" stands for "community") is an Experimental Internet Protocol defined in RFC 1901, RFC 1905, and RFC 1906. SNMPv2c is an update of the protocol operations and data types of SNMPv2p (SNMPv2 Classic), and uses the community-based security model of SNMPv1.
*SNMPv3 - Version 3 of SNMP. SNMPv3 is an interoperable standards-based protocol defined in RFCs 2273 to 2275. SNMPv3 provides secure access to devices by a combination of authenticating and encrypting packets over the network.
SNMP Security Models and Levels
Model
Level
Authentication
Encryption
What Happens
v1
noAuthNoPriv
Community String
No
Uses a community string match for authentication.
v2c
noAuthNoPriv
Community String
No
Uses a community string match for authentication.
v3
noAuthNoPriv
Username
No
Uses a username match for authentication.
v3
authNoPriv
MD5 or SHA
No
Provides authentication based on the HMAC-MD5 or HMAC-SHA algorithms.
v3
authPriv
MD5 or SHA
DES
Provides authentication based on the HMAC-MD5 or HMAC-SHA algorithms. Provides DES 56-bit encryption in addition to authentication based on the CBC-DES (DES-56) standard.
Reference:
http://www.cisco.com/c/en/us/td/docs/ios/12_2/configfun/configuration/guide/ffun_c/fcf014.h tml