User-Based Security Model; Cli And Snmp User Synchronization - Cisco Nexus 5600 Series Configuration Manual

SNMPv3

User-Based Security Model

SNMPv3 User-Based Security Model (USM) refers to SNMP message-level security and offers the following
services:
• Message integrity—Ensures that messages have not been altered or destroyed in an unauthorized manner
and that data sequences have not been altered to an extent greater than can occur nonmaliciously.
• Message origin authentication—Confirms that the claimed identity of the user who received the data
was originated.
• Message confidentiality—Ensures that information is not made available or disclosed to unauthorized
individuals, entities, or processes.
SNMPv3 authorizes management operations only by configured users and encrypts SNMP messages.
Cisco NX-OS uses two authentication protocols for SNMPv3:
• HMAC-MD5-96 authentication protocol
• HMAC-SHA-96 authentication protocol
Cisco NX-OS uses Advanced Encryption Standard (AES) as one of the privacy protocols for SNMPv3 message
encryption and conforms with RFC 3826.
The priv option offers a choice of DES or 128-bit AES encryption for SNMP security encryption. The priv
option and the aes-128 token indicates that this privacy password is for generating a 128-bit AES key #.The
AES priv password can have a minimum of eight characters. If the passphrases are specified in clear text, you
can specify a maximum of 64 characters. If you use the localized key, you can specify a maximum of 130
characters.
For an SNMPv3 operation using the external AAA server, you must use AES for the privacy protocol in
Note
user configuration on the external AAA server.

CLI and SNMP User Synchronization

SNMPv3 user management can be centralized at the Access Authentication and Accounting (AAA) server
level. This centralized user management allows the SNMP agent in Cisco NX-OS to leverage the user
authentication service of the AAA server. Once user authentication is verified, the SNMP PDUs are processed
further. Additionally, the AAA server is also used to store user group names. SNMP uses the group names to
apply the access/role policy that is locally available in the switch.
Any configuration changes made to the user group, role, or password results in database synchronization for
both SNMP and AAA.
Cisco NX-OS synchronizes user configuration in the following ways:
• The auth passphrase specified in the snmp-server user command becomes the password for the CLI
user.
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Configuring SNMP
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