Chapter 7. Configuring the Simple Network Management Protocol (SNMP) Feature

The Model S20 software includes an SNMP agent, a software module that responds to SNMP requests. To manage a 7318 using SNMP, you will need a third-party SNMP manager, a program that generates SNMP requests.

The Model S20 SNMP agent supports MIB-II (Management Information Base) as described in RFC 1213 (a document publicly distributed on the Internet). In addition to MIB-II, it supports three additional MIBs:

• Character MIB (RFC 1316)
• RS-232 MIB (RFC 1317)
• Parallel Port MIB (RFC 1318)

These MIBs define the most common requests to the 7318, namely to the ports on the 7318.

Note: Any configuration changes made with an SNMP manager will be temporary changes. To make permanent configuration changes, you need to modify the configuration file that gets downloaded when the 7318 boots.

Prerequisites

1. You must be in password privilege mode on the 7318.
2. You must have root user authority.

Procedure

Some of the MIB variables such as the system location are blank in the default configuration file. To return meaningful values for these variables, you need to add them to the [SNMP] section of the configuration file.

The default configuration file allows you to use SNMP to get variables from the 7318 using the public community. To add communities or modify the access rights of public community, you need to modify the configuration file.

Finally, the Model S20 software will issue certain SNMP traps. It will only do so, however, if the target managers are listed in the configuration file.

The following information describes how to update the configuration file with SNMP-related information (such as system variables, communities, and traps).

Configure System Variables

Certain information is normally provided by all SNMP-managed devices, such as their description. Default values for some of these items are computed by the system. Other values such as the location are blank by default. You can override these values by specifying values in the SNMP section of the configuration file. The values that you can override are shown in the following table:

The following procedure provides an example of how to set these variables:

To define the contact who administers a 7318:

1. Use a text editor to modify the configuration file for your 7318.
2. Locate the [SNMP] section.
3. Modify the sysContact entry as in the following example:

   sysContact=Jack Smith, Room 327, Ext. 123

4. Write the file and exit the editor.
5. When all users have logged off the 7318, reboot it to reload the modified configuration file.

Configure Communities

Rudimentary security for SNMP is provided by the use of communities. You can use the configuration file to specify what managers the Model S20 agent will respond to and whether the manager can modify the 7318 configuration (temporarily) or only read it. The default configuration file provides read-only access to all managers in the public community.

To add a new community:

1. Use a text editor to modify the configuration file for your 7318.
2. Locate the [SNMP] section.
3. Add one to the value of the ncommunities entry. For example, if the old value was 1, the new entry would be:

   ncommunities=2 

4. Add a new [Community] section whose number is one less than the value of the ncommunities entry. For example, if ncommunities=2 , then the new section would be:

   [Community01] 

5. Add entries to this new section similar to the following:

   name=private 
   mgrAddress=192.132.4.3 
   access=readWrite

   The name is the name of the community. The mgrAddress is the Internet address of manager node in dotted decimal notation or 0.0.0.0 to accept any manager in this community. The access type is read to allow the manager to get SNMP variables only, readWrite to allow the manager to get and set variables, or none to disable access for this manager.
6. Write the file and exit the editor.
7. When all users have logged off the 7318, reboot it to reload the modified configuration file.

Configure Traps

The Model S20 SNMP agent has the ability to issue SNMP traps in response to system events. An SNMP trap is a datagram from the S20 agent to an SNMP manager indicating that some event on the 7318 has occurred. The agent will only send these traps, however, to managers that are listed in the configuration file.

The following traps are issued by the S20 SNMP agent:

Each manager who is sent traps is listed in a separate section of the configuration file. The number of these trap sections is defined by the ntraps entry in the [SNMP] section.

To send traps to a new manager:

1. Use a text editor to modify the configuration file for your 7318.
2. Locate the [SNMP] section.
3. Add one to the value of the ntraps entry. For example, it the old value was 1, the new entry would be:

   ntraps=2

4. Add a new [TrapNN] subsection whose number is one less than the value of the ntraps entry. For example, if ntraps=2 , then the new subsection would be:

   [Trap01] 

5. Add entries to this new section similar to the following:

   name=private
   mgrAddress=192.132.4.3
   port=162

   The name is the name of the community. The mgrAddress is the Internet address of manager node in dotted decimal notation or 255.255.255.255 to broadcast to all managers in this community. The port is the UDP port where the trap is to be sent. It is optional and defaults to 162.
6. Write the file and exit the editor.
7. Use the reboot command from the 7318 command shell or power-cycle the 7318 to load the modified configuration file.