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Cisco ONS 15600 SDH Reference Manual, Release 9.0
78-18400-01
Chapter 13 SNMP
13.5 SNMP Message Types
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View-Based Access Control Model
—The view-based access control model controls the access to
the managed objects. RFC 3415 defines the following five elements that VACM comprises:
–
Groups—A set of users on whose behalf the MIB objects can be accessed. Each user belongs to
a group. The group defines the access policy, notifications that users can receive, and the
security model and security level for the users.
–
Security level—The access rights of a group depend on the security level of the request.
–
Contexts—Define a named subset of the object instances in the MIB. MIB objects are grouped
into collections with different access policies based on the MIB contexts.
–
MIB views—Define a set of managed objects as subtrees and families. A view is a collection or
family of subtrees. Each subtree is included or excluded from the view.
–
Access policy—Access is determined by the identity of the user, security level, security model,
context, and the type of access (read/write). The access policy defines what SNMP objects can
be accessed for reading, writing, and creating.
Access to information can be restricted based on these elements. Each view is created with different
access control details. An operation is permitted or denied based on the access control details.
You can configure SNMPv3 on a node to allow SNMP get and set access to management information
and configure a node to send SNMPv3 traps to trap destinations in a secure way. SNMPv3 can be
configured in secure mode, non-secure mode, or disabled mode.
SNMP, when configured in secure mode, only allows SNMPv3 messages that have the authPriv security
level. SNMP messages without authentication or privacy enabled are not allowed. When SNMP is
configured in non-secure mode, it allows SNMPv1, SNMPv2, and SNMPv3 message types.
13.5 SNMP Message Types
The ONS 15600 SDH SNMP agent communicates with an SNMP management application using SNMP
messages.
describes these messages.
Table 13-1
ONS 15600 SDH SNMP Message Types
Operation
Description
get-request
Retrieves a value from a specific variable.
get-next-request Retrieves the value following the named variable; this operation is often used to
retrieve variables from within a table. With this operation, an SNMP manager does
not need to know the exact variable name. The SNMP manager searches
sequentially to find the needed variable from within the MIB.
get-response
Replies to a get-request, get-next-request, get-bulk-request, or set-request sent by
an NMS.
get-bulk-request Fills the get-response with up to the max-repetition number of get-next interactions,
similar to a get-next-request.
set-request
Provides remote network monitoring (RMON) MIB.
trap
Indicates that an event has occurred. An unsolicited message is sent by an SNMP
agent to an SNMP manager.
