23-2
Catalyst2950 Desktop Switch Software Configuration Guide
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Chapter23 Configuring SNMP
Understanding SNMP
•Using SNMP to Access MIB Variables, page 23-4
•SNMP Notifications, page 23-5
SNMP Versions
This software release supports these SNMP versions:
•SNMPv1—The Simple Network Management Protocol, a Full Internet Standard , define d i n
RFC 1157.
•SNMPv2C replaces the Party-based Administrative and Security Framework of SNMPv2Classic
with the community-string-based Administrative Framework of SNMPv2C while retaining the b ulk
retrieval and improved error handling of SNMPv2Classic. It has these features:
–
SNMPv2—Version 2 of the Simple Network Management Protocol, a Draft Internet Standard,
defined in RFCs 1902 through 1907.
–
SNMPv2C—The community-string-based Administrative Framework for SNMPv2, an
Experimental Internet Protocol defined in RFC 1901.
•SNMPv3—Version 3 of the SNMP is an interoperable standards-based protocol defined in RFCs
2273 to 2275. SNMPv3 provides secure access to devices by authenticating and encrypting packets
over the network and includes these security features:
–
Message integrity—ensuring that a packet was not tampered with in transit
–
Authentication—determining that the message is from a valid sou rce
Both SNMPv1 and SNMPv2C use a community-based form of security. The community of managers
able to access the agent’s MIB is defined by an IP address access control list and password.
SNMPv2C includes a bulk retrieval mechanism and more detailed error message reporting to
management stations. The bulk retrieval mechanism retrieves tables and lar ge qua ntities of inf ormation,
minimizing the number of round-trips required. The SNMPv2C imp roved error-han dl ing inc lude s
expanded error codes that distinguish different kinds of error conditions; these conditions are repo rted
through a single error code in SNMPv1. Error return cod es in SN M Pv2 C r eport the erro r ty pe.
SNMPv3 provides for both security models and security levels. A security model is an authentication
strategy set up for a user and the group within which the user resides. A security level is the permitted
level of security within a security model. A combination of the security level and the security model
determine which security mechanism is used when handling an SNMP pack et. Available security models
are SNMPv1, SNMPv2C, and SNMPv3.
Table23-1 identifies the characteristics of the different combinations of security models and levels.
Table23-1 SNMP Security Models and Levels
Model Level Authentication Encryption Result
SNMPv1 noAuthNoPriv Community string No Uses a community string m atch for authentication.
SNMPv2C noAuthNoPriv Community string No Uses a community string m atch for authentication.
SNMPv3 noAuthNoPriv Username No Uses a username match for authentication.
SNMPv3 authNoPriv MD5 or SHA No Provides authentication based on the HMAC-MD5
or HMAC-SHA algorithms.