SNMP Security Models and Levels

Definitions:

• Security model is a security strategy used by the SNMP agent

• Security level is the permitted level of security within a security model

Definitions:

• Security model is a security strategy used by the SNMP agent

• Security level is the permitted level of security within a security model

Model	Level	Authentication	Encryption	What Happens
v1	noAuthNoPriv	Community String	No	• Authenticates with a community string match
v2	noAuthNoPriv	Community String	No	• Authenticates with a community string match
v3	noAuthNoPriv	Username	No	• Authenticates with a username
	authNoPriv	MD5 or SHA	No	• Provides HMAC MD5 or SHA algorithms for authentication
	authPriv	MD5 or SHA	DES	• Provides HMAC MD5 or SHA algorithms for authentication • Provides DES 56-bit encryption in addition to authentication based on the CBC-DES (DES-56) standard

A security model is an authentication strategy that is set up for a user and the group in which the user resides. Currently, Cisco IOS software supports three security models: SNMPv1, SNMPv2, and SNMPv3.

A security level is the permitted level of security within a security model. The security level is a type of security algorithm performed on each SNMP packet. There are three security levels:

■ noAuth: Authenticates a packet by a string match of the user name or community string.

■ Auth: Authenticates a packet by using either the Hash-based Message Authentication Codes (HMACs) with Message Digest 5 (MD5) (RFC 2104) or Secure Hash Algorithms (SHAs).

■ Priv: Authenticates a packet by using either the HMAC MD5 or SHAs, and encrypts the packet using the Cipher Block Chaining-Data Encryption Standard (CBC-DES) (DES-56) algorithm.

SNMPv3 adds security and remote configuration capabilities to the previous versions. SNMPv3 provides three security model and security level options. The table in the figure identifies the combinations of security models and levels.

Implementing Secure Converged Wide Area Networks (ISCW) v1.0

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In its natural evolution, the current version of SNMPv3 addresses the vulnerabilities of earlier versions by including three important services: authentication, privacy, and access control.

Continue reading here: Configuring NTP Authentication

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