Technical data

Configuring SNMP
13.4 Configuring SNMP
writeit Read Write 9.20.208.53
trapit Read Trap 9.20.208.53, 9.20.208.100
In this example, the configuration allows read access to any client on any host
through the
"public" community and read/write access to the client on host
9.20.208.53 through the "writeit" community. In addition, trap messages are
sent to UDP port 162 on hosts 9.20.208.53 and 9.20.208.100.
Alternatively, you can display the configuration options in the SNMP
configuration text file described in Section 13.4.3. See Section 13.6.5.2 for
more information.
13.4.3 SNMP Options
You can configure the way SNMP runs by entering SNMP options into the SNMP
configuration file TCPIP$VMS_SNMP_CONF.DAT.
When it starts, the SNMP master agent creates the temporary file
SYS$SYSDEVICE:[TCPIP$SNMP]TCPIP$TMP_SNMP_CONF.DAT from data in
the standard TCP/IP configuration database file TCPIP$CONFIGURATION.DAT.
A few versions of this file are preserved in case they are needed for
troubleshooting. The master agent appends this temporary file to TCPIP$VMS_
SNMP_CONF.DAT to produce the master configuration file TCPIP$SNMP_
CONF.DAT.
When the standard OS_MIBS and HR_MIB subagents start up, they read
TCPIP$SNMP_CONF.DAT. Only the master agent and these standard subagents
use values in the text files.
By default, custom subagents do not take advantage of the configuration options.
To take advantage of these options, you must assign a logical that is visible to
the subagent process. The following example shows how to define TCPIP$SNMP_
GEN_LOGFILE logical to set the
snmp_gen_logfile configuration option:
$ ASSIGN/SYSTEM 1 TCPIP$SNMP_GEN_LOGFILE
If a configuration option is not handled by the eSNMP API, the subagent must
include an explicit
genenv( ) or similar call to access the value of the option.
13.4.3.1 Using Logical Names to Configure SNMP
Most configuration options have a corresponding logical name. In some cases,
you can define system logical names as an alternative to entering a value in the
text file. See Section 13.4.3.4 for a list of the options and their associated logical
names.
13.4.3.2 Dynamic Options
Some options are available for you to change dynamically; that is, without
shutting down and restarting the SNMP service. To change configuration values
dynamically, you can do one of the following:
• Define the appropriate logical name.
• Edit the configuration file, then define
snmp_signal to be sighup . Be sure
to deassign snmp_signal afterwards to prevent continuous rereading of the
configuration file.
Configuring SNMP 13–9