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14.4.2 Displaying the Current SNMP Configuration

To display configuration information in the SNMP configuration database, use the SHOW CONFIGURATION SNMP command. If you want to display the addresses that the agent recognizes as members of the community, use the /FULL qualifier. For example:

SNMP Configuration 
Flags:    AuthenTraps  Sets 
Contact:  Sam Spade 
  First:  Falcon Building 
  Second: Los Angeles, CA 
Community           Type       address_list 
public              Read 
writeit             Read Write 
trapit              Read Trap, 

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 through the writeit community. In addition, trap messages are sent to UDP port 162 on hosts and

Alternatively, you can display the configuration options in the SNMP configuration text file described in Section 14.4.3. For more information, see Section

14.4.3 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. For troubleshooting purposes, a few versions of this file are preserved. 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:


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. 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. For a list of the options and their associated logical names, see Section 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: Modifying the Configuration File

The master agent and the subagents convert lines in the configuration file that begin with the OpenVMS-specific config command to user-mode process logicals by adding the prefix TCPIP$. For example, SNMP_GEN_LOGFILE becomes TCPIP$SNMP_GEN_LOGFILE. (This mechanism does not apply to options with other keywords, such as trap .) Because the logicals are local to agent processes, they are not visible to a DCL command SHOW LOGICAL issued in another process.

If there are lines with duplicate configuration tags, the last line supersedes all others. Because the temporary file TCPIP$TMP_CONF.DAT (described in Section 14.4.3) is appended after the user-editable TCPIP$VMS_SNMP_CONF.DAT file, the standard TCPIP configuration values from that temporary file always supersede those from the user-edited file.

Lines in the configuration file that begin with a pound sign (#) are ignored. The pound sign is the comment character.

Option names and values are not case sensitive. Boolean values are considered on if the option is present with no value. Otherwise, they are considered off. Thus, to turn off an option that was enabled at startup, you must specify zero as the value.

If you specify a value that is longer than the limit, the value is converted to hexadecimal and then truncated. For example, if you specify the value 257 in place of an 8-bit unsigned value, it is converted to hexadecimal (0101) and truncated to 1. SNMP Configuration Options

Most of the SNMP options set in the TCPIP$VMS_SNMP_CONF.DAT file must be entered using the following syntax:

config option-name value

There are several types of SNMP configuration options:

Except for the community name, option values are not case sensitive.

Table 14-3 SNMP Logging Options
Format: config SNMP_GEN_LOGFILE 1
Description: Redirects messages to SYS$OUTPUT and records them in the following files:
  • TCPIP$ESNMP_SERVER process-id.LOG, where process-id is the 8-digit hexadecimal process identifier of the master agent.
  • TCPIP$ESNMP_RESIDENT_SUBAGENT process-id.LOG, where process-id is the 8-digit hexadecimal process identifier of the resident subagent.
  • TCPIP$OS_MIBS process-id.LOG, where process-id is the 8-digit hexadecimal process identifier of the MIB II subagent.
  • TCPIP$HR_MIB process-id.LOG, where process-id is the 8-digit hexadecimal process identifier of the Host Resources MIB subagent.
Type: Dynamic
Description: Specifies whether a timestamp is included in the log message. If not defined, a timestamp is included. The value can be 1 (to prevent timestamp information from being included) or 0 (to allow timestamp information to be included; the default).
Type: Dynamic
Description: Specifies whether to log detailed information or not. The value can be 1 (to log detailed information) or 0 (to log the default amount of information).
Type: Dynamic

Table 14-4 SNMP Operation Options
Logical name: Not available
Format: COMMUNITY name address type
Description: Specifies the community name. See Section 14.4 for more information about specifying a community name.
Type: Dynamic
Logical name: Not available
Description: This configuration option reflects the setting of the /FLAGS=AUTHENTICATION qualifier to the SET CONFIGURATION SNMP command and is included in the configuration file for backward compatibility. This option in the configuration file is ignored.
Type: Not dynamic
Format: config SNMP_RESTARTS 5
Description: Specifies the maximum number of times to restart a subagent. The default for OS_MIBS and HR_MIB is 3.
Type: Not dynamic
Format: config SNMP_SELECT_ERROR_LIMIT 500
Description: Specifies the number of iterations for the error limit. The default value is 100.
Type: Not dynamic
Description: Simulates a UNIX-style signal that affects the way agents operate.

Following is a list of values:

  • SIGUSR1---causes a dump of MIB registration area with contexts to the following log file:
  • SIGHUP---rereads the configuration file.
  • SIGINT---causes the process to exit.
  • SIGTERM---same as SIGINT.
  • SIGUSR2---turns on tracing.
  • SIGCHLD---turns off tracing.

Do not set this option in the configuration text file. After setting the logical name, be sure to reset it to prevent system performance problems.

Type: Dynamic
Logical name: Not available
Format: SYSNAME host-name
Description: Specifies the SNMP host name. This host name is used only by SNMP. You can reset the host name by editing this option and then restarting the master agent.
Type: Not dynamic
Logical name: Not available
Format: SYSCONTACT contact-information
Description: Specifies the contact information.

Do not modify this option. Use TCPIP$CONFIG or the SET CONFIGURATION SNMP command to change the information associated with this option.

Type: Not dynamic
Logical name: Not available
Format: SYSLOCATION host-location
Description: Specifies the host or contact location information.

Do not modify this option. Use TCPIP$CONFIG or the SET CONFIGURATION SNMP command to change the information associated with this option.

Type: Not dynamic
Logical name: Not available
Format: trap trap-name version IP-address
Description: Specifies:
  • The name of the trap ( trap-name).
  • Whether to trap for SNMP Version 1 requests only ( version). Specify V1 for Version 1 traps only. Specify V2C for both Version 1 and Version 2 traps.
  • The internet address of the client ( address). Do not specify for the client address.

For information about setting individual trap types depending on the destination host, see Section

Type: Not dynamic

Table 14-5 Timing and Timeout Handling Options
Format: config AGENTX_SESSION_TIMEOUT seconds
Description: Specifies the default timeout for a session between a subagent and the master agent. Subagents can supersede this value when they register their MIBs.

The value of this option is used by both the master agent and the subagent. Normally, all subagents running on the same host have the same timeout value, which is specified by this option.

When the subagent reads the value of this option, the value is interpreted as follows:

  • If the option is not defined, the default value of 3 seconds is assumed.
  • If the option is set to 0, the timeout value used by the master agent is used.
  • If the option is set to a nonzero integer, that value is used instead of the master agent's default timeout value.

When the master agent reads the value of this option, the value is interpreted as follows:

  • If the option is not defined, the default value of 3 seconds is assumed.
  • If the option is set to a value greater than 0, this timeout value is used, unless a different value has been specified for the subagent.
  • Do not set the value of this option to 0.

The maximum value you can specify is 255. This option can be used to increase the timeout for communication between the master agent and subagents on a slow system.

Type: Dynamic
Format: config SNMP_MASTER_TIMEOUT seconds
Description: Specifies (in seconds) the default time to wait listening for an SNMP request. The default is 10 seconds.
Type: Not dynamic
Format: config SNMP_ARE_YOU_THERE_TIME seconds
Description: Specifies the time subagents wait between sending the esnmp_are_you_there() message to the master agent.

For the OS_MIBS and the HR_MIB, the default is 5400 seconds (90 minutes).

If you also specify the SNMP_INACT_TIME option, make sure the value of the SNMP_ARE_YOU_THERE_TIME option is less than or equal to the value of the SNMP_INACT_TIME option.

Type: Dynamic
Format: config SNMP_POLL_TIME seconds
Description: Specifies the interval between times that interface counts and other values are reset for standard subagents.
Type: Dynamic
Format: config SNMP_INACT_TERM n
Description: In this format, n can be 1 (to terminate the master agent) or 0 (to never terminate the master agent). Specify the amount of time to wait using the SNMP_INACT_TIME option.
Type: Dynamic
Format: config SNMP_INACT_TIME seconds
Description: Specifies (in seconds) the amount of time that must pass before the subagent is considered inactive (that is, the amount of time during which the master agent receives no message from the subagent). See also the SNMP_INACT_TERM and SNMP_ARE_YOU_THERE_TIME options.
Type: Dynamic

Time-related parameters are important in determining the responsiveness of the SNMP agents to client requests, particularly on systems with limited memory or those that are heavily loaded.

On startup, each subagent first sets up a default session timeout (see the AGENTX_SESSION_TIMEOUT option). It then registers its MIB regions. The subagent can register each of its MIB regions with a different timeout. A value of 0 causes the session timeout for the entire subagent to be used.

The master agent listens for SNMP requests. The timeout value is 10 seconds, unless the SNMP_MASTER_TIMEOUT option has been defined. After a timeout occurs, the master agent updates counters, checks for requests, then loops to wait for another SNMP request. When an SNMP request arrives, the master agent determines which if any registered subagents can handle it. It then resets the SNMP_MASTER_TIMEOUT timeout to use the maximum of the timeouts for all MIB regions involved.

When it is not processing an SNMP request, a subagent may send are_you_there messages to the master agent at a default interval determined by the subagent. For the chess example, the default is 30 seconds; for the OS_MIBS and HR_MIB subagents, the default is 5400 seconds (90 minutes). Both values are derived from those used in the UNIX implementation of SNMP; the second value was set high to minimize system overhead.

The following relationships among configuration option values are recommended but are not enforced. See the descriptions of the specific options for details.

Table 14-6 Testing and Troubleshooting Options
Logical name: Not available
Format: accept IP-address
Description: If nonlocal subagents are allowed (using the SNMP_ALLOW_INET_TRANSPORT, AGENT_INET_ADDR, or AGENTX_INET_PORT option), the ACCEPT option specifies the IP address of the host from which a connection will be accepted. If these options are not set, connections from nonlocal subagents are rejected. To allow access from all subagents, specify the IP-address as
Type: Dynamic
Format: config AGENTX_LOCAL_PORT port number
Description: Specifies the local port number from which to accept nonlocal subagent connections.
Type: Dynamic
Format: config AGENTX_INET_PORT port number
Description: Specifies the TCP/IP port number from which to accept connections from nonlocal subagents.
Type: Dynamic
Description: Specifies whether the master agent accepts connections from nonlocal subagents.
Type: Dynamic
Logical name: TCPIP$SNMP_TRACE
Format: config TCPIP$SNMP_TRACE n
Description: Allows you to direct trace log messages to standard log files when agents are running in normal production mode. (Alternatively, you can get trace logs while running the subagent in interactive mode, as described in Section 14.6.4.)

Running with tracing produces a great deal of output and may slow down the system. In addition, utilities like the MIB browser ( snmp_request ) may need a longer timeout interval when running with tracing on.

The type of data and the amount of data logged for custom subagents depends on how the subagents are programmed, except for the logging that is handled automatically by the eSNMP API routines. The chess example code provides some samples of using the ESNMP_LOG macro.

Type: Not dynamic

Table 14-7 Backward-Compatibility Options
Description: In this format, n can be 1 (to set the option), or 0 (to turn the option off). If this option is set, a subagent that tries to register with the same name as a previously registered subagent will be rejected. By default, duplicate registrations are allowed; the AgentX protocol does not check for duplicate subagents based on the subagent name.
Type: Dynamic
Format: config SNMP_V1_TRAP_DEFAULT n
Description: In this format, n can be 1 (to set the option), or 0 (to turn the option off). When this option is set, traps defined in the TCPIP$CONFIG.COM procedure or using the TCP/IP management command SET CONFIGURATION SNMP are sent in SNMP Version 1 format. The default is to send these types of traps in Version 2 format.
Type: Dynamic

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