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Compaq TCP/IP Services for OpenVMS

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The -c and -p options send the query to the specified host immediately. If you omit the host names, the default is the local host. To enter interactive mode, specify the -i or -n option.

12.9 Solving NTP Problems

Some common NTP problems include:

  • Out of synch system clock.
    The NTP cannot synchronize a clock that is off by more than 1000 seconds. To solve this problem, set the clock using TCPIP$NTPDATE, then restart the NTP.
  • NTPDATE fails to set the clock.
    This occurs if the NTP is already running.
  • More than one service is actively setting the system clock.
    The NTP can run with other time services but must be explicitly instructed not to set the system clock. NTP can still provide synchronization to other clients even if it is not updating the system clock.
  • NTP appears to be running without error, but the system clock is off by a one, two, three, or four-hour interval.
    You may need to adjust the time zone differential by running SYS$COMMON:[SYSMGR]UTC$CONFIGURE_TDF.COM. (See Section 12.5 for more information.)

Chapter 13
Configuring SNMP

The Simple Network Management Protocol (SNMP) is network management technology that facilitates the management of a TCP/IP network or internet in a vendor-independent manner. SNMP enables a network administrator to manage the various network components using a set of well-known procedures understood by all components, regardless of the vendor that manufactured them.

Configuring SNMP on your OpenVMS system allows a remote SNMP management client to obtain information about your host and to set system and network parameters.

This chapter reviews key concepts of SNMP and describes:

For information about writing programs using SNMP, refer to the Compaq TCP/IP Services for OpenVMS SNMP Programming and Reference guide.

13.1 Key Concepts

Systems using SNMP are divided into two categories:

  • Management consoles, sometimes called clients, network management stations, or directors
  • Agents, sometimes called servers

The management console is the system that issues a query; the agents run on the system being queried. Queries are sent and received in the form of protocol data units (PDUs) inside SNMP messages, which are carried in user data protocol (UDP) datagrams.

You can configure your host so that an SNMP client can obtain information about your host and perform updates on your host's management information base (MIB) data items. For example, you can configure your host to:

  • Respond to a client's read requests ("Gets") for network information.
  • Process client write requests ("Sets") on your host's MIB data items.
  • Send alert messages ("traps") to a client as a result of events that might need to be monitored (for example, an authentication failure).

TCP/IP Services provides an SNMP master agent, two subagents (MIB II and Host Resources MIB), a MIB converter and compiler, a simple MIB browser, and MIB utility programs. Each subagent contains routines that perform read and write operations on its MIB data items.

Table 13-1 describes the SNMP components and the sample code supplied for custom subagent development.

Table 13-1 SNMP Components
Component Description
Master agent SNMP Version 2 Process name: TCPIP$SNMP_ n, where n is the number of times that the master agent has been started since the SNMP service was enabled.

Keeps track of managed objects and allows objects to register themselves. Sends information about these objects to remote SNMP management consoles. Also maintains a small set of variables for the MIB II component.

MIB II Process name: TCPIP$OS_MIBS.

Provides information about the TCP/IP protocol stack and other network activity.

Host resources MIB Process name: TCPIP$HR_MIB.

Provides information about the host system.

MIB converter Extracts a MIB definition in ASN.1 notation into a MIB definition (.MY) file.
MIB compiler Compiles MIB-definition files (for example, CHESS_MIB.MY) into source code templates for use in building subagents.
SNMP utility programs Acts as a simple clients to obtain a set of values for a MIB and to listen for and send trap messages. For information about using the MIB utility programs, see the Compaq TCP/IP Services for OpenVMS SNMP Programming and Reference guide.
SNMP subagent example Implements an example based on the chess game; includes executable and source code.

13.1.1 Understanding How SNMP Operates

The TCPIP$CONFIG procedure sets up the SNMP UDP-based service at well-known port 161.

In addition, TCPIP$CONFIG sets up required files in the SYS$SYSDEVICE:[TCPIP$SNMP] directory.

The SNMP startup procedure (SYS$STARTUP:TCPIP$SNMP_STARTUP.COM) runs from the general TCPIP$STARTUP.COM procedure or can be run directly by the system manager.

TCPIP$SNMP_STARTUP.COM does the following:

  1. Checks the TCP/IP Services license and enables the SNMP service.
  2. Installs images with the required privileges (as appropriate: BYPASS, PHY_IO, and WORLD).

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.

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.

13.2 Managing the SNMP Service

The following command procedures are supplied to allow you to start up and shut down the SNMP service independently of TCP/IP Services:

  • SYS$STARTUP:TCPIP$SNMP_STARTUP.COM allows you to start up the SNMP service.
  • SYS$STARTUP:TCPIP$SNMP_SHUTDOWN.COM allows you to shut down the SNMP service.

Both the startup and shutdown procedures invoke the appropriate TCPIP$EXTENSION_MIB_*.COM file to ensure compatibility with previous versions of TCP/IP Services.

These files might be overwritten when you install subsequent versions of the TCP/IP Services product. For more information about these procedures, see Section 13.1.1.

To maintain site-specific SNMP logical names, commands, and parameter settings, you can create the following files:

  • SYS$STARTUP:TCPIP$SNMP_SYSTARTUP.COM can be used as a repository site-specific definitions and parameters to be invoked when SNMP is started.
  • SYS$STARTUP:TCPIP$SNMP_SYSHUTDOWN.COM can be used as a repository for site-specific definitions and parameters to be invoked when SNMP is shut down.

Installing this version of TCP/IP Services will:

  1. Purge existing TCPIP$SNMP_SYSTARTUP.COM and TCPIP$SYSHUTDOWN.COM files, leaving only the latest version.
  3. Install new versions of TCPIP$SNMP_SYSTARTUP.COM and TCPIP$SYSHUTDOWN.COM files.

To preserve earlier versions of these files, copy them to another directory. New versions of TCP/IP Services will include instructions for merging the contents of the old versions with the current one.

13.3 Verifying the SNMP Installation

A separate installation verification procedure (IVP) exists for SNMP. To verify your configuration, complete these steps:

  1. Log in to the SYSTEM account, or make sure that your process has the following privileges:
    • TMPMBX
    • NETMBX
    • SETPRV
  2. Run the command procedure:

  3. Enter option 7 (Run tests), and then option 2 from the Compaq TCP/IP Services for OpenVMS Test menu.
    Note that, like the Internet IVP, the SNMP IVP requires that TCP/IP Services be running. (It does not require that SNMP be running.)
  4. To run the SNMP IVP any time after exiting the configuration procedure, enter the following command:


13.3.1 SNMP Executable and Command Files

Table 13-2 lists the names of the primary SNMP executable and command files and their locations. For a list of files that help you build your own subagent, see the Compaq TCP/IP Services for OpenVMS SNMP Programming and Reference guide.

Table 13-2 SNMP Executable, Command, and Data Files
File Location Function
TCPIP$HR_MIB.EXE SYS$SYSTEM Host Resources MIB subagent image.
TCPIP$SNMP_TRAPSND.EXE SYS$SYSTEM Program for sending trap messages.
TCPIP$SNMP_TRAPRCV.EXE SYS$SYSTEM Program for receiving trap messages.
TCPIP$ESNMP_SHR.EXE SYS$SHARE Routines in the eSNMP application programming interface (API).
TCPIP$SNMP_STARTUP.COM SYS$STARTUP Installs master and subagent images and runs TCPIP$SNMP_RUN.COM.
TCPIP$SNMP_RUN.COM TCPIP$SYSTEM Starts the master agent and subagents.
TCPIP$SNMP_SHUTDOWN.COM SYS$STARTUP Stops the master agent and subagents.
TCPIP$SNMP_SYSTARTUP.COM SYS$STARTUP Sets site-specific configuration values on startup.
TCPIP$SNMP_SYSHUTDOWN.COM SYS$STARTUP Sets site-specific configuration values on shutdown.
  SYS$SYSDEVICE:[TCPIP$SNMP] Starts custom subagents.
  SYS$SYSDEVICE:[TCPIP$SNMP] Shuts down custom subagents.
TCPIP$VMS_SNMP_CONF.DAT SYS$SYSDEVICE:[TCPIP$SNMP] User-editable configuration data file.
TCPIP$SNMP_CONF.DAT SYS$SYSDEVICE:[TCPIP$SNMP] Configuration data file used in the startup of the master agent and standard subagents.

13.4 Configuring SNMP

You can configure SNMP in three ways, which may be used in combination:

  • Using the standard TCPIP$CONFIG.COM procedure and the SET CONFIGURATION SNMP command. These methods write configuration information into the TCP/IP Services configuration database file TCPIP$CONFIGURATION.DAT. Section 13.4.1 describes how to use TCPIP$CONFIG to initially configure SNMP.
  • Editing the text configuration file TCPIP$VMS_SNMP_CONF.DAT, located in the SYS$SYSDEVICE:[TCPIP$SNMP] directory. This method provides options not available with TCPIP$CONFIG and the SET CONFIGURATION SNMP command.


    Although the OpenVMS SNMP configuration file is based on the UNIX implementation, there are several important differences. For example, the option snmpEnableAuthenTraps is not used. See the description of specific options for details.

    The configuration file is described in Section 13.4.3.
  • Assigning logical names. This method provides the same options as the text configuration file. For more information, see Section 13.4.3.

If the same option is defined in multiple ways, the configuration methods are resolved as follows:

  • Values specified through TCPIP$CONFIG or SET CONFIGURATION SNMP take precedence over any options specified in the TCPIP$VMS_SNMP_CONF.DAT file or set with logical names.
  • Values specified in the TCPIP$VMS_SNMP_CONF.DAT file take precedence over logical name settings.

13.4.1 Initial SNMP Configuration

SNMP runs as a TCP/IP service. To be sure all SNMP-related files are included and enabled properly, run the TCPIP$CONFIG configuration procedure to configure SNMP initially or to set up a new configuration. When you enable SNMP during TCPIP$CONFIG, the procedure prompts you for the correct parameters.


You cannot use TCPIP$CONFIG to modify your existing SNMP configuration; TCPIP$CONFIG is intended only to set up a new SNMP configuration.

To modify the current SNMP configuration (for example, to specify an additional community name and address), you must enter the SET CONFIGURATION SNMP command with applicable qualifiers.

When you run TCPIP$CONFIG after a TCP/IP Services upgrade, be sure to disable and then reenable the SNMP service.

You supply the following information about your host when you configure SNMP initially during TCPIP$CONFIG or when you issue the SET CONFIGURATION SNMP command to modify your existing SNMP configuration. For detailed information about the SET CONFIGURATION SNMP command and qualifiers, see the Compaq TCP/IP Services for OpenVMS Management Command Reference manual.

  • The name of the person to contact about the system. For example:

  • The physical location of the system. For example:

    _TCPIP> /LOCATION=(FIRST="Falcon Building",SECOND="Los Angeles, CA")
  • The community information used to authenticate requests from a network manager and to determine the addresses to which trap messages are sent.
    SNMP network management clients are grouped into communities as specified in RFC 1157. You can define one or more communities, which your master agent uses to authenticate requests.
    The parameters you specify for each community are as follows:
    • Community name
      The name associated with the community. The standard community is "public." You can choose to not provide this community name when you run TCPIP$CONFIG. Answer No to the question "Do you want to provide the public community." If you disable the public community, you may need to reconfigure SNMP clients in your environment.
      Community names are case sensitive. When you use TCPIP$CONFIG to specify a community name, do not use quotation marks to preserve the case. The case is preserved exactly as you enter it. However, if you customize your existing SNMP configuration using the SET CONFIGURATION SNMP command, make sure you enclose the community name in quotation marks to preserve the case. If you do not enclose the community name in quotation marks, the name is changed to all uppercase.
      The community name must be a string of alphanumeric characters. You cannot include a space or other nonalphanumeric character in the community name.
      You can also modify the community name using the community option in the configuration file, as described in Table 13-4.
    • Community address
      The address associated with the community. One community name can have multiple addresses in its entry. For example:


      Specifying address for READ and WRITE allows any host the type of access specified. To allow any network manager to monitor your system remotely, specify the standard community name ( public , in lowercase letters) with address For example:


      Traps are sent to UDP port 162 on hosts for all trap addresses regardless of community name. The use of address on a trap means that traps are not sent unless another address is also specified.
    • Types of access
      The types of access associated with the community are described in the following table:
      Access Type Allows the Master Agent and Subagent to...
      READ Respond to a client's read requests (gets) for network information. Default. Members of a read-only community do not have write access to the SNMP MIB objects.
      TRAP Send alert messages (traps) to a client as a result of unusual events. For example, a trap message is sent to the client as a result of a get request that specifies an unauthorized community string ( authenticationFailure ).
      WRITE Process client write requests (sets) on your host's MIB data items.

For example, to allow the master agent to respond to client get requests, enter:


To configure your host to allow client set requests, use the /FLAGS=SETS qualifier. For example:


13.4.2 Displaying the Current SNMP Configuration

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


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 13.4.3. See Section for more information.

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