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Packet Sniffer and MIB Browser

-Input the IP address of your SNMP remote into the "Address:" field.
-Click the "Advanced..." button and specify the appropriate IP port (default is 161 for most SNMP devices) and any other necessary settings for your SNMP remote.

Specify IP Address and Port Number

1. Return to Ethereal and start a new Live Capture. Start new Live Capture
2. In MIB browser, send a Get to your SNMP remote. Any GetResponses received will appear in the list on the right of the screen. If you receive no GetResponses, make sure that you have correctly specified the IP address and port number for your SNMP RTU. If you still do no receive GetResponses, you have a network problem or your RTU is not sending traps properly. Get Responses
3. Return to Ethereal and stop the Live Capture. Stop Live Capture

  • Examine the packets captured by Ethereal, looking for SNMP in the "Protocol" column -You can sort packets by protocol by click the "Protocol" column header to group all SNMP packets together

Sort By Protocol

  • If your traps are incorrectly addressed, they will never reach your manager.
    -If traps are coming through but not displayed on your SNMP manager, your SNMP RTU may simply be sending traps to the wrong IP address. Check for this problem in the "Destination" IP address column in Ethereal.
  • If your traps appear to be correctly addressed, you may have a problem with your SNMP manager configuration.
    -To further isolate the problem to your SNMP manager, you may use the Trap Sender in MIB Browser to send test traps
    to your SNMP manager while you monitor its display. The Trap Sender is located in the Tools menu. Simply specify
    the IP address of your manager and a few other settings, then click the blue triangle button to send a test trap. If these
    test traps are not displayed by your SNMP manager, the problem is almost certainly with the configuration of your manager.

Trap Sender MenuSend Trap

  • If you received no SNMP traps, you must check your network and RTU configurations separately to determine the cause of the problem. One good next step is to identify another PC on the network that is as close to your SNMP remote as possible (ideally connected via Hub to ensure complete visibility in Ethereal). Install Ethereal and MIB Browser on that PC and repeat this procedure. By conducting the test as close to your RTU as possible, you will minimize the effect of firewalls and other potential network problems. If you still do not see traps in Ethereal after testing again, your SNMP remote may not be sending traps properly, or at all.

Next Page: How to Verify
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