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Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
OL-8978-04
Chapter 47 Configuring SNMP
Understanding How SNMPv3 Works
Figure 47-1
SNMP Entity for Traditional SNMP Agents
Message Processing Subsystem
The message processing subsystem accepts the outgoing PDUs from the dispatcher and prepares them
for transmission by wrapping them in a message header and returning them to the dispatcher. The
message processing subsystem also accepts the incoming messages from the dispatcher, processes each
message header, and returns the enclosed PDU to the dispatcher. An implementation of the message
processing subsystem may support a single message format corresponding to a single version of SNMP
(SNMPv1, SNMPv2c, SNMPv3), or it may contain a number of modules, each supporting a different
version of SNMP.
Security Subsystem
The security subsystem authenticates and encrypts the messages. Each outgoing message is passed to
the security subsystem from the message processing subsystem. Depending on the services required, the
security subsystem may encrypt the enclosed PDU and some fields in the message header. In addition,
the security subsystem may generate an authentication code and insert it into the message header. After
encryption, the message is returned to the message processing subsystem.
v1MP
v2c MP
v3MP
UDP
IPX
Other
Message Dispatcher
Proxy
foward
applications
MIB Instrumentation
Command
responder
applications
Notification
originator
applications
Transport Mapping
PDU Dispatcher
SNMP Entity
SNMP Engine
Access Control
Subsystem
Security
Subsystem
Message Processing
Subsystem
Dispatcher
View-based
access control
model
User-based
security
model
Other
security
model
Other
access control
model
SNMP Applications
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otherMP
