Community names are passwords used by the SNMP agent to restrict access to information provided by the MIB. In order to retrieve information from the MIB, NNM needs to be configured with the community name of every device. The global default for community names in NNM is set to "public." This allows SNMP read access to devices that do not have a read community name configured.
You can configure community names in NNM by selecting Options
Figure 5-4. To configure the community name, provide the IP address or hostname as the Target, the get (read) community name, and the set (write) community name and click the
[Add] button. If community names are not specified, the Global Default will be used. Wildcards and numeric ranges may be used only when specifying the device's IP address.
Individual hostname targets will be listed in the top section of the dialog box, sub-titled
Specific Nodes . You cannot use wildcards (*) when specifying hostnames. The next section of the dialog box, sub-titled
IP Address Wildcards , permits IP addresses to be specified using wildcards (*) and also allows for the specification of IP address ranges. For example, if a certain type of network device in your enterprise ends with a 1 in the last octet and is configured with the same community name, you can specify the IP addresses using a wildcard:
156.155.*.1
Similarly, if you would like to specify a range of IP addresses with the same community name use the target
156.155.[201-210].1
You can also combine IP address wildcards and ranges:
156.[150-153].*.1
The agent configuration, not to be confused with the management station configuration, will vary based on the type of system. One area that may cause some confusion is the fact that the management station itself also must have an SNMP agent running on it. In this respect, it is just like any other managed node. Most Unix systems have a configuration file such as /etc/snmpd.conf. To configure the SNMP agent, modify the get-community-name and set-community-name entries. Sample entries in the snmpd.conf are shown. The trap-dest will usually be set to your NNM management station. This is the location to which to send agent initiated SNMP traps. Multiple trap destinations can be defined in this file in the case that more than one SNMP management station exists.
The SNMP agent configuration should include the following entries:
get-community-name: mickey set-community-name: mouse trap-dest: 156.155.204.8
After the changes have been made to the SNMP agent configuration, you will need to restart the SNMP agent. This process varies based on the agent you are running. NNM ships with the SNMP Research® EMANATE agent. This agent uses a master/sub-agent technology, which requires a restart of the SNMP master agent and the sub-agents. Use the following steps to add community names and restart the EMANATE agent:
UNIX:
Modify
/etc/snmpd.conf with the get-community-name and the set-community-name.
get-community-name: mickey
set-community-name: mouse
Stop the master and sub-agents.
/sbin/init.d/SnmpMaster stop
Start the master and sub-agents.
/etc/snmpd
Verify SNMP communication to the hostname.
snmpwalk <hostname> system
Windows:
Use the Notepad[4] editor to modify the file
[4] Some editors cannot handle files with four character extensions.
%OV_CONF%\ SNMPAgent\snmpd.conf
with the get-community-name and the set-community-name as follows:
get-community-name: mickey
set-community-name: mouse
Restart the SNMP agent service. The
Services are accessible from
Control Panel for Windows NT and the
MCC for Windows 2000. Scroll down the list until you reach the SNMP EMANATE Adapter for Windows and SNMP EMANATE Master Agent.
Select the
Windows Adapter and
Stop the process. You will be prompted for confirmation.
Select the
Master Agent and
Start the process.section 5.1.3 for troubleshooting. You can test the set-community-name through the NNM GUI by attempting to set a read-write MIB variable such as system contact. Follow these steps to test the set-community-name of a MIB variable:
From the NNM GUI, select a node that has a set-community-name configured and start the MIB Browser by selecting
Tools
SNMP
MIB
Browser
Traverse the subtree:
mgmt.mib-2.system
Select the variable
sysContact and click
[Start Query] .
Verify the MIB value. You should see the instance[6]
0 and no contact information unless the contact was previously set.
[6] The instance will always be 0 unless there are multiple instances for the variable. For example, if there are multiple file systems there will be a unique instance number for each file system and the instance will begin with 1.
Set the
sysContact by entering the MIB Instance 0, the set-community-name and click
[Set] . The SNMP Set Value must match the set-community-name string you entered in the snmpd.conf (or the agent configuration) file.