Technical data
Configuring SNMP
13.1 Key Concepts
To ensure compatibility with previous versions of TCP/IP
Services, TCPIP$SNMP_SYSTARTUP.COM in turn runs
SYS$SYSDEVICE:[TCPIP$SNMP]TCPIP$EXTENSION_MIB_STARTUP.COM,
which installs and adjusts privileges for any additional, user-written subagents.
On startup, the TCP/IP Services kernel runs the TCPIP$SYSTEM:TCPIP$SNMP_
RUN.COM procedure, which does the following:
• Purges log files in the SYS$SYSDEVICE:[TCPIP$SNMP] directory.
• Runs the subagent image as a detached process.
• Runs SYS$SYSDEVICE:[TCPIP$SNMP]TCPIP$EXTENSION_MIB_
RUN.COM to start any additional subagents.
As each subagent starts, it makes itself known to the master agent, a sequence
that includes registering the MIB subtrees that the subagent maintains and
communicating the port number on which it listens.
Once SNMP starts, the following sequence occurs for each incoming SNMP
request. This sequence is standard for SNMP implementations.
1. The master agent listens for incoming SNMP requests from clients on port
161. Authentication is limited to the validation of the community name.
When a request arrives, the master agent communicates with the appropriate
subagent.
2. Subagent routines collect the requested data and return the data to the
master agent.
3. The master agent responds to the client from which the original request was
made.
The SNMP shutdown procedure TCPIP$SNMP_SHUTDOWN.COM runs either
from the general shutdown procedure TCPIP$SHUTDOWN.COM or can be run
directly by the system manager.
TCPIP$SNMP_SHUTDOWN.COM does the following:
• Stops subagent processes and removes the SNMP images.
• Runs the SYS$STARTUP:TCPIP$SNMP_SYSHUTDOWN.COM procedure.
To ensure compatibility with previous versions, this procedure in turn
runs SYS$SYSDEVICE:[TCPIP$SNMP]TCPIP$EXTENSION_MIB_
SHUTDOWN.COM, which stops any additional subagent processes and deinstalls
their images, if necessary.
13.1.2 Ensuring Access to Mounted Data
If the proxy setup between the SNMP server and the NFS server is not correct,
the Host Resources MIB subagent cannot access data that has been mounted.
To ensure access to mounted data, set up a proxy to an anonymous user (for
example, to TCPIP$NOBODY) on the NFS server system. For more information
about adding proxy entries, see Chapter 20.
Configuring SNMP 13–3