Checking the SNMP reachability

How to check the SNMP reachability of network devices

Site24x7's On-Premise Poller uses SNMP to monitor and collect performance metrics from monitored devices. 

You can check if a network device or a server is reachable through SNMP from the On-Premise Poller using:
  1. Site24x7's MIB browser 
  2. The MIB browser in the machine where the On-Premise Poller is installed
  3. Command-line tools

Testing using Site24x7's MIB browser

To check if a device is reachable through SNMP using the MIB browser in Site24x7: 
  1. Log in to your Site24x7 account. 
  2. Navigate to Network > Device Templates.
    1. Select an existing device template (if available for the device) and click the pencil  icon in the Action column on the same row. If a device template is not available, click Add Device Template.
    2. On the page that opens, click Add Custom Performance Counters and select RFC-1213 MIB.
    3. Select the required metric in the left pane. This will populate the value on the right side.
    4. Then, click Test to open the Test Performance Counter pop-up.

      Figure 1. Testing a performance counter to see if the value is fetched from the device in Site24x7's MIB browser. 
  3. In the Test Using field, select Monitor Name or IP Address as needed. 
  4. If you select Monitor Name:
    1. Select an option for Monitor Name from the drop-down menu.
    2. Select the credential in the Credential Name field.
    3. Verify the SNMP OID and the Type of the performance counter.
    4. Click Test.

      Figure 2. Testing a performance counter using the Monitor Name. 
  5. If you select IP Address:
    1. Enter the value in the IP address field.
    2. Select the correct On-Premise Poller.
    3. Select the credential in the Credential Name field.
    4. Verify the SNMP OID and the Type of the performance counter.
    5. Click Test.

      Figure 3. Testing a performance counter using the IP Address.
  6. You will see the value mapped to the SNMP OID associated with that performance counter if the test is successful.

Testing using the MIB browser in the On-Premise Poller-installed machine

Please follow the steps below to check if a network device or a server is reachable through SNMP, from the On-Premise Poller using the bundled MIB browser: 
  1. Open the Command Prompt as an administrator. From here, go to the directory where the On-Premise Poller is installed. If the Command Prompt isn't opened as an administrator, an Access is denied error message is displayed.
  2. Navigate to the ../Site24x7OnPremisePoller/Networkplus/bin folder.
  3. Execute the MibBrowser.sh or MibBrowser.bat file
  4. Set the SNMP credentials with respect to the version.
    1. For SNMP v1, set the host, port, and the SNMP community.
    2. For SNMP v2, click Edit > Settings > Change the SNMP version > OK. Set the host, port, and the SNMP community.
    3. For SNMP v3, click Edit > Settings > Change the SNMP version > Add. Set the host, port, username, authentication credentials and click OK.
        
      Figure 4. Testing an OID in the MIB browser in machine where the On-Premise Poller is installed. 
  5. Then, navigate the RFC1213-MIB to org.dod.internet.mgmt.mib-2.system.sysObjectID (or) set the value for Object ID field to .1.3.6.1.2.1.1.2.
  6. Click the Get SNMP variable icon (the seventh icon from the left) below the menu bar.
  7. Check if the device details were fetched successfully.

    Figure 5. Checking if the value was fetched correctly.
If a timeout occurs, please check if
i) The hostname, port, and SNMP community are specified correctly.
ii) There is a firewall blocking the SNMP connection. 
iii) The On-Premise Poller is on the same network as the device.
There is also a chance that the On-Premise Poller will not be on the list of hosts that are allowed to query the device through SNMP. Check the SNMP configuration on the device to ensure it's configured correctly.  

Testing using command-line tools

If the MIB browser is inaccessible or fails to work, SNMP command-line tools can be used to check the SNMP reachability.
  1. Install the required packages:
    Fedora/Centos: yum install net-snmp-utils
    Ubuntu: apt-get install snmp
  2. Execute the appropriate commands:

    SNMP v1/v2c:
    > snmpwalk -v     [1/2c] -c <Read_Community> <IP_Address>
    Example: snmpwalk -v 1 -c public 10.10.10.1

    SNMP v3:
    > snmpwalk -v3 -l (noAuthNoPriv | authNoPriv | authPriv) -u (username) [-a (MD5 | SHA)] [-A (authphrase)] [-x DES] [-X (privaphrase)] (ipaddress)[:(dest_port)]
    Example: snmpwalk -v3 -u testuser -A ‘password@123’ -l authNoPriv -a MD5 10.10.10.1:161
    If the SNMP port is not default 161, specify the correct port in the above command as IP_Address:Port.
    Example: 10.10.10.1:601