Appendix A. The MIB Browser

The MIB Browser is available through either pvcontrolpanel or pvgraph. It lets you select a node on your network and view and change the contents of one or more Management Information Bases (MIBs) for that node. Browser communicates with a node that you select using Simple Network Management Protocol (SNMP). The node can be a workstation, router, bridge, hub, or gateway—any device that has an IP address and implements the SNMP protocol and agent.

Several MIB specifications are provided with Browser. The supplied MIB specifications are:

Browser is designed to be used by network managers experienced in managing various devices on the network. This section assumes that you are familiar with SNMP management terminology and technology, especially the MIBs for different devices. If you are not familiar with this terminology, the section titled “SNMP Management Glossary” defines the basic terms.

This section explains how to

In addition, an example of using Browser is provided. For complete information on Browser command line options, see the browser(1M) reference page.


Note: To enable Browser to get and set MIB variables on a Silicon Graphics workstation, that workstation must be running the SNMP daemon snmpd(1M), and your Display Station must be authorized in the file /etc/snmpd.auth on that workstation. See “Authorizing Browsing” for details.



Caution: With proper authorization, Browser lets you change some MIB variable values on devices you browse. Because MIB variable values can be critical to the operation of a device and your network, do not change values unless you understand the effects of your changes.


SNMP Agents

Browser uses Simple Network Management Protocol (SNMP) agents to obtain information. The SNMP agent for Silicon Graphics workstations is snmpd(1M). Vendor-specific SNMP agents are used to obtain information about other types of nodes (see Figure A-1). For more information on SNMP see the section titled “SNMP Management Glossary.” For information on enabling SNMP agents, see “Enabling SNMP Agents.”

Figure A-1. SNMP Agents and Browser


Enabling SNMP Agents

Browser must communicate with the SNMP agent on each node you wish to browse. SNMP agents and the procedures for enabling them are vendor-specific. The procedure for enabling the SNMP agent on Silicon Graphics workstations is described below. For other types of nodes, contact the system administrator for that node for help in enabling SNMP on that node.

The Silicon Graphics SNMP agent is snmpd(1M). The SNMP agent software is distributed with IRIX, and the hp-ux_sgi MIB and agent are distributed with provision. To configure a workstation so that snmpd is started automatically when the system is rebooted, copy the snmpd executable file to the workstation, and enter this command on the workstation as root:

chkconfig -f snmpd on 

To see if the daemon is already running, enter this command:

ps -e | grep snmpd 

If there is no output from this command, snmpd is not running. Enter this command as root to start snmpd:

snmpd 

Authorizing Browsing

No special authorization other than a valid community string is required to browse on nodes other than Silicon Graphics workstations. (See “Browser Main Window” and “SNMP Management Glossary” for more information about community strings.)

If you want to get and set MIB variables on a Silicon Graphics workstation using Browser, you must perform several setup steps in addition to providing a valid community string while using Browser: confirm that the workstation you are browsing has SNMP agent software running; start it if necessary (see “Enabling SNMP Agents,” in this chapter); and authorize your Display Station to browse on that workstation.

To be authorized to browse a Silicon Graphics workstation, the Display Station's host name must be specified in the file /etc/snmpd.auth on the workstation you are browsing. You must be superuser (root) to read or write /etc/snmpd.auth. For security reasons, the owner and permissions of this file should not be changed.

As an example, suppose that you want to browse a Silicon Graphics workstation named tahoe. Your workstation's name is sequoia. First, confirm that snmpd is running on tahoe:

rsh guest@tahoe 'ps -e | grep snmpd' 

Assuming that it is running, log onto tahoe as superuser and add this line to /etc/snmpd.auth:

accept sequoia:* 

This line authorizes anyone using your workstation to browse the workstation tahoe when they give any community string. These users can perform both get and set operations.

By default, /etc/snmpd.auth contains this authorization line:

accept  *:public/get

This line authorizes any user from any host who provides the community public to get variable values for this workstation.

See the snmpd(1M) reference page and the file for more information about the syntax used in this file.

About the Browser

Browser enables you to walk the tree of information represented by the MIBs and the SNMP Containment Tree, and to get the values of MIB variables. While you are using Browser, you can save the variable values that you receive to a file. You can set MIB variables if the SNMP and MIB implementations on the node you are browsing allow it and the community string you provide authorizes it.

Starting Browser

To start Browser, click the browser button from a provision window.

The Browser main window appears. An example is shown in Figure A-2.

Figure A-2. Browser Main Window


Browser Main Window

The entry fields in the Browser main window enable you to specify the node you wish to browse, a community string, a time-out value for accessing the SNMP agent on the node, and the number of retries to make when attempting to access a remote node.

When you invoke Browser, the entry field shown in Figure A-3 contains the name of your workstation. You can replace it with the name or address of the node you want to browse. A blank entry field is the same as specifying the name of your workstation.

Figure A-3. Node Entry Field


The Community entry field shown in Figure A-4 contains the community string that is to be used in the SNMP packets sent to the node. The community string is an authorization password for the node you browse on. On Silicon Graphics workstations, valid community strings and other authorization information is specified in the file /etc/snmpd.auth. The default community string on Silicon Graphics workstations is “public.” For other types of nodes, such as routers and bridges, the community string is specified for each device by a system administrator. A valid community string must be supplied in order to use Browser to view MIB information.

Figure A-4. Community Entry Field


If Browser doesn't receive a reply from the SNMP agent on the specified node within the time-out value, it will try again. The default time-out value, shown in Figure A-5, is 5 seconds.

Figure A-5. Time-out Interval Entry Field


The Number of retries entry field, shown in Figure A-6, specifies the number of retries when there has been no reply from the node. The default is 3.

Figure A-6. Number of Retries Entry Field


The mib-2, enterprises, and experimental buttons in the Browser main window, shown in Figure A-7, provide quick ways to specify what you want to browse: the mib-2 MIB, or the enterprises or experimental nodes in the SNMP Containment Tree, respectively. When you click these buttons, a Subtree window appears. Subtree windows and Table windows are described in the next section. These buttons are grayed out if no MIB specifications in that portion of the SNMP Containment Tree are available to Browser. The term ``grayed out'' means that the button title is gray at that moment, rather than black. This indicates that the function or service represented by that button is unavailable.

Figure A-7. mib-2, enterprises, and experimental Buttons


When you click the Variable... button, shown in Figure A-8, a Variable window appears. This window is used to get and set the values of specific MIB variables. It is explained in detail in “Obtaining and Setting Values Using the Variable Window” in this chapter.

Figure A-8. Variable... Button


Browser Subtree and Table Windows

To display MIB information, Browser uses two types of windows: Subtree windows and Table windows. For every nonleaf node in the SNMP Containment Tree, Browser displays one of these types of windows:

  • a Subtree window showing the subtrees of that node

  • a Subtree window showing the variables and/or tables of that node

  • a Table window showing the array of table variables in that table

The remainder of this section discusses examples of these windows.

Subtree Windows That Show Subtrees

Figure A-9 shows the Subtree window for mib-2. It is an example of a Subtree window for a subtree that contains other subtrees.

Figure A-9. Subtree Window Showing Subtree Objects


The Node entry field, shown in Figure A-10, contains the node name or address you specified in the Browser main window.

Figure A-10. Node Entry Field


The Object ID and Name entry fields, shown in Figure A-11, contain two different representations of the name of the subtree displayed in the window. The Object ID entry field contains the numeric representation of the name (dot separated object numbers) and the Name entry field contains the text string representation (dot-separated object names).

Figure A-11. Object ID and Name Entry Fields


The scrolling display area in the center of the window contains one line for each object in the subtree, such as the udp line shown in Figure A-12. The line begins with the object's number in curly braces followed by its object name. Clicking the Open group... button brings up a Subtree window for the object on this line. Its use is described more fully in “Navigation Using Buttons in the Subtree and Table Windows” in this chapter. A grayed-out button means there are no variables under this object in the MIB.

Figure A-12. Object in a Display Area


The Read At line provides status information during a “get” operation (see “Obtaining, Setting, and Saving Variable Values” in this chapter), which is replaced by the current time after the operation is completed. An example is shown in Figure A-13.

Figure A-13. Read At Line


The current time is displayed on the Set At line after a “set” operation (see “Obtaining, Setting, and Saving Variable Values” in this chapter). An example is shown in Figure A-14.

Figure A-14. Set At Line


Checking the “Close this window when opening a subwindow” check box, shown in Figure A-15, specifies that you want this Subtree window to be closed when a new Subtree or Table window for a node in this subtree is opened. By default, each of the Subtree or Table windows you open for subtrees or tables within this subtree will have the same setting.

Figure A-15. “Close This Window When Opening a Subwindow” Check Box


Subtree Windows That Show Variables and Tables

Figure A-16 shows the Subtree window for mib-2.udp. It is an example of a Subtree window that shows the variables and/or tables of that subtree (in MIB terminology, this type of subtree is called a group).

Figure A-16. Subtree Window Showing Variables and a Table


Most portions of this type of Subtree window are the same as the Subtree windows described in “Subtree Windows That Show Subtrees” in this chapter. However, the display area of this type of Subtree window contains entry fields and Open table... buttons rather than Open group... buttons.

Variables in the subtree are shown in the display area as an object number, an object name, and an entry field, as shown in Figure A-17. When the object number (in braces) is appended to the object ID at the top of the window, it forms the complete object ID for the object. The entry field is gray for variables whose values are defined as read-only in the MIB and pink for variables that are defined as read-write or write-only in the MIB. If the entry field is pink, you can set the value of that variable (see “Obtaining and Setting Values Using the Edit Menu of a Subtree Window,” in this chapter).

Figure A-17. Variable Line in a Subtree Display Area


Tables in the subtree have lines that include their object number, their name, and the Open table... button, as shown in Figure A-18. When you click an Open table... button, a Table window, described in the next section, appears.

Figure A-18. Table Line in a Subtree Display Area


Browser Table Windows

Figure A-19 shows the default Table window for mib-2.udp.udpTable. When a Table window appears, the display area contains only the names of the table variables. Entry fields appear for the variables as you retrieve their values with “Get next row” in the Edit menu. (See “Obtaining and Setting Values Using the Edit Menu of a Table Window,” in this chapter.)

Figure A-19. Browser Table Window


Navigating the SNMP Containment Tree

With Browser you can open a Subtree window for each subtree in an MIB that you want to browse and a Table window for each table in an MIB that you want to browse. Browser buttons and menus enable you to specify the subtree or table you want to view. When you use these buttons and menus, you are “navigating” the MIB Tree. The three navigation methods are described in the following sections.

Navigation Using the Buttons in the Main Window

The mib-2, enterprises, and experimental buttons in the Browser main window provide three starting points for browsing the SNMP Containment Tree. Clicking the mib-2 button brings up a Subtree window for the MIB-II MIB. Clicking the enterprises and experimental buttons brings up Subtree windows for the Enterprises and Experimental subtrees, respectively.

Navigation Using the Navigate Menu

To use the Navigate menu from any window, follow these steps:

  1. Press the left mouse button on Navigate in the menu bar.

    In the menu that appears, each choice except the last is the name of a subtree or table that is an object in the subtree in the window. Choices are highlighted as you move the cursor on them; if they have a rollover menu, it appears automatically. Figure A-20 shows an example of the Navigate menu at the mib-2 subtree with the cursor on udp.

    Figure A-20. Navigate Menu


  2. To view one of the subtrees of the subtree in the window, select one of the choices on the Navigate menu (not on a rollover menu).

    If you make the subtree selection shown in Figure A-20, the window shown in Figure A-16 appears.

  3. To view subtrees or tables farther down in the hierarchy, move the cursor to a choice on a rollover menu and release the mouse button. In this way you can traverse the entire width and length of the subtree in the window.

  4. To view the parent of the current subtree, select the last choice on the Navigate menu. It is the name of the parent of the subtree in the window.

Navigation Using Buttons in the Subtree and Table Windows

Figure A-9 shows an example of Open group... buttons in the display area of the mib-2 Subtree window. When you click one of these buttons, a new Subtree window appears for this object. It is equivalent to choosing this subtree from the Navigate menu.

In Figure A-16, udpTable is a table and has an Open table... button. Clicking an Open table... button is equivalent to choosing the table from the Navigate menu. Figure A-19 shows the Table window for udpTable that appears when you click this button.

Obtaining Descriptions of Variables

To get a description of each of the objects in a subtree or each of the variables in a table, select “Description” from the Help menu of the Subtree or Table window. A Description window appears. Figure A-21 shows an example.

Figure A-21. Description Window


Obtaining, Setting, and Saving Variable Values

Browser enables you to obtain the values of MIB variables and set them if you have write access. (Write access is determined by the type of the variable and by your community. See “Authorizing Browsing” and “SNMP Management Glossary.”) Three types of Browser windows can be used to get and set variables:

Obtaining and Setting Values Using the Variable Window

Follow the steps below to use the Variable window to get and set variable values.

  1. Click the Variable... button in the Browser main window. The window shown in Figure A-22 appears.

    Figure A-22. Variable Window


  2. If you want to specify a variable by object identifier, fill in the Object ID entry field with the object identifier and append the following:

    .0 
    

    The “dot zero” specifies that you want the value of the object; if you forget to use .0, Browser adds it automatically. For example, to specify mib-2.ip.ipForwarding (1.3.6.1.2.1.4.1), the Object ID entry field should look like the one shown in Figure A-23.

    Figure A-23. Object ID Entry Field


  3. To specify a variable in a table, enter its object identifier in the Object ID entry field. To construct its object identifier, you can use the object identifier of the table and append:

    .1.x.y 
    

    The column number is represented by x (beginning with 1), and y is the value of index for the row you want. For example, the object identifier for the ifDescr variable (column 2) in the first row (index value of 1) of the mib-2.interfaces.ifTable (1.3.6.1.2.1.2.2) table is 1.3.6.1.2.1.2.2.1.2.1. If the table you are using has more than one index column, create y by specifying each index value in order and separating them with periods. For example, if the value of index1 is 127.1.9 and the value of index2 is 7, y is 127.1.9.7.

  4. If you want to specify the variable by name, fill in the Name entry field. You need not type in the complete hierarchical name, just the last component. Adding .0 to the name is optional. If the Object ID and the name you fill in don't match, the Object ID is used.

  5. To obtain the value of the variable, click the Get button. The value of the variable appears in the Value entry field. The Name entry field is automatically modified so that it contains the complete hierarchical name.

  6. To set the value of a variable, enter the value in the Value entry field and click the Set button.

  7. To obtain the value of the next variable, click the Get next button. Depth-first search is used to determine the next variable, so the right-most component of the object identifier varies fastest as the tree is traversed with Get next.

  8. Continue obtaining and setting variables as necessary by modifying the Object ID, Name, and/or Value entry fields and using the Get, Get next, and Set buttons.

Obtaining and Setting Values Using the Edit Menu of a Subtree Window

You can obtain and set the values of variables from a Subtree window using the Edit menu:

  1. Bring up the Subtree window that contains the variable whose value you want to obtain or set (see “Navigating the SNMP Containment Tree” in this chapter).

  2. Select Get from the Edit menu to obtain the values of all of the variables. The current time is displayed on the Read At line.

  3. Make changes in the entry fields for any variables whose values you want to change. Only variables whose entry fields are pink may be changed.

  4. Select Set from the Edit menu to change variable values. The current time is displayed on the Set At line.

Obtaining and Setting Values Using the Edit Menu of a Table Window

You can obtain and set the values of variables in a table from its Table window using the Edit menu:

  1. Bring up the Table window for the table you are interested in (see “Navigation Using the Navigate Menu” in this chapter).

  2. To obtain the first row of variables in the table, select “Get next row” from the Edit menu. The current time is displayed on the Read At line.

  3. To obtain other rows for the table, select “Get next row” from the Edit menu as many times as necessary.

  4. Make changes in the entry fields for any variables whose values you want to change.

  5. Select Set from the Edit menu to change variable values. The current time is displayed on the Set At line.

Browser File Menu

The File menu in each window gives you one or more of the window management and quitting choices listed below.

Save MIB Values 


Save MIB values for this subtree for all nodes in the subtree that have open windows to a file. The values are appended to the file that you last specified with Save MIB Values As... .

Save MIB Values As... 


Save MIB values for this subtree for all nodes in the subtree that have open windows to a file. When you select this choice, a file prompter appears. Use it to specify a filename. The filenames are sorted by object identifier.

Pop Main Window 


Display the Browser main window. This is useful if you have many windows open and want to locate the Browser main window quickly.

Close Lower Level Windows 


Close the windows for all subtrees and tables below the subtree in this window. (You can close windows automatically as new windows are opened, using the check box “Close this window when opening a subwindow.” See “Subtree Windows That Show Subtrees,” in this chapter.)

Close 

Close this window.

Quit 

Quit Browser (available only from the File menu in the Browser main window).

Browser Example

This section contains an example Browser session on a network that contains a Cisco® router with IP address 192.26.51.27.

To begin this session, invoke Browser through provision.

The Browser main window is placed on the screen. To browse the MIB for the Cisco router, first fill in the entry fields in the Browser main window:

Node 

Enter the Cisco router's IP address, 192.26.51.27.

Community 

Enter the community string your workstation is authorized to use. In this example, the string public is used.

Time-out interval 


Use the default value, 5 seconds, for the time-out interval. If the Browser doesn't receive a reply from the Cisco SNMP agent in 5 seconds, it will try again.

Number of retries 


Use the default number of retries, which is 3. This entry field specifies the number of times that Browser tries again if no reply is received from the Cisco agent within the time-out interval.

Figure A-24 shows the Browser main window after you've filled in the entry fields.

Figure A-24. Example Browser Main Window


Suppose you want to get the values for the lsystem group in the Cisco MIB. To display the variables in this group, use the Navigate rollover menus to navigate through the MIB hierarchy to lsystem, as shown in Figure A-25.

Figure A-25. Navigate Rollover Menus for cisco.local.lsystem


When you release the mouse button, the Cisco Subtree window shown in Figure A-26 appears:

Figure A-26. Subtree Window for cisco.local.lsystem


To get the values for these variables, select Get from the Edit menu. The entry fields for the variables are filled in with their current values, and the current time is indicated at the bottom of the window. Figure A-27 shows an example:

Figure A-27. Subtree Window With Values for cisco.local.lsystem


Use the right scroll bar to adjust the display area so that you can examine the values of the variables that don't fit in the default-size display area.

SNMP Management Glossary

This section describes some basic terms used in the SNMP management framework. It begins with basic concepts. Later definitions build on terms defined previously. Terms in italics are defined elsewhere in this section.

Agent

Software or firmware that gathers the information important to the device on which it resides. It also implements a protocol that exchanges that information with a network management station. snmpd(1M) is an example of an SNMP agent.

Network Management Protocol

The protocol used to convey management information between an agent and a network management application. The protocol used by Browser to query information from various agents is SNMP.

Simple Network Management Protocol (SNMP)

The network management protocol used by Browser to talk to agents on remote managed nodes. For Silicon Graphics workstations, the SNMP agent is snmpd(1M). Agents for other types of nodes may be implemented in software or firmware and are vendor-specific.

Management Information Base (MIB)

The specification for the virtual store of the information supported by an agent. Some MIBs have RFC status, which means they have been approved by the IETF.

MIBs are defined in SMI format. For instance, a router MIB is a collection of important information about a router defined in SMI format. An SNMP agent typically implements two MIBs, MIB-II and a device-specific MIB (an Enterprise MIB). However, the agent may not implement all of the objects defined in each MIB.

SNMP Containment Tree

A hierarchical tree of information gathered by agents about devices.

Subtree

A node with children in the SNMP Containment Tree.

MIB-II

The Internet-standard MIB (RFC 1213). This MIB has managed objects that are important for managing the TCP/IP suite of protocols.

Managed Object

A managed object is also known as a variable.

Variable

A leaf node in the SNMP Containment Tree is called a variable. In the SMI definition for each MIB, each variable is defined to be read-write, read-only, or write-only.

Object Identifier (Object ID)

An object identifier is a name in a dot notation that uniquely identifies an object (subtree or managed object) in the MIB. For example, the object ID for sysContact is 1.3.6.1.2.1.1.4.

Enterprise MIBs

MIBs defined by different vendors for managing their devices. They can be specific to one device or vendor. For example, the CISCO MIB has objects for the Cisco router.

Community String

A password used by an SNMP agent for authentication purposes. The default string for Silicon Graphics workstations is “public.” Community strings are usually defined by system administrators.