About Vacm - Network Critical SmartNA-X User Manual

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Manager functions
Table 9-2
Operation
get-request
get-next-request
get-bulk-request
get-response
set-request
trap
inform
Table 9-2 SNMP manager operations
1. SNMPv2 only.
Community strings
An SNMP community string is a text string used to authenticate messages between a management station and an
SNMP v1/v2c engine. Community strings are superseded by SNMPv3 groups, which provide better security.
However, since there are many managers still using SNMPv1/v2c, community strings continue to be widely used
for authenticating access to the agent.
MIB access
The SNMP agent gathers data from the MIB. The agent can send notifications of certain events to the SNMP
manager, which receives and processes the notifications. Notifications are messages alerting the SNMP manager to
a condition on the network such as improper user authentication, restarts, link status (up or down), TAP module
in/out, and so forth. The SNMP agent also responds to MIB-related queries sent by the SNMP manager in get-
request, get-next-request, and set-request format.
For information on supported MIBs, see

About VACM

When connecting with SNMPv1 or SNMPv2c, the only identification mechanism available is community strings.
For clients using SNMPv1/v2c, you can define community strings on SmartNA-X (SNMP > Traditional access
control: > Configure Communities) and ignore all the VACM options if you wish.
When connecting with SNMPv3, there is an alternative mechanism for identification and access control: VACM.
In this case, you provide a certain user's credentials instead of a community string. On the SmartNA-X device,
users belong to groups, available settings are collected into views, and the access control list determines which
groups can access which views. This system allows for much more flexibility in both user configuration and view
configuration than is available with the community string mechanism, not to mention robust privacy and
authentication mechanisms, though at the expense of being more complicated to set up.
lists the functions used by SNMP managers to request information, set values and set up notifications.
Description
Retrieves a value from a specific variable.
Retrieves a value from a variable within a table.
1
Retrieves large blocks of data that would otherwise require the transmission of many small
blocks of data, such as multiple rows in a table.
Replies to a get-request, get-next-request, and set-request sent by an NMS.
Stores a value in a specific variable.
An unsolicited message sent by an SNMP agent to an SNMP manager when some event has
occurred. Traps are not acknowledged by the receiver, so the sender has no way of knowing if
the trap was received or not.
An unsolicited message sent by an SNMP agent to an SNMP manager when some event has
occurred. Unlike traps, informs are acknowledged with an SNMP response PDU.
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Appendixl G, "Supported MIBs", page
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