I have been asked, if Advantech routers can send SNMP Traps? The answer is YES. The next question is, can they send SNMP Trap on configurable exceptions? There is no short answer, only a long one.
Quick details
There is an easy way to solve some problems. Normally you would poll your devices for status information. This is perfectly fine. What that means though is that you need to have something like Elasticsearch to actually get meaningful information from all those information retrieved via polling.
Another approach can be a mixed approach. Where some values are retrieved from the routers by polling and some are sent as SNMP traps on exception.
NOTE: Advantech routers do send predefined SNMP Trap periodically and that can be enabled in configuration (see below for list of values send in this SNMP Trap)
I have made a simple User Module, which does add functionality of sending specific values on change and some values have a variation field to be set. This allows for a more reasonable approach to receiving valuable information.
Short guide
User module does send initial values when enabled to the SNMP Trap Listener. After that it will take reading of the values based on the Interval setting. Taking into consideration the variation when configured.
In case the variation is not configured any change in value is considered a change.
You can find description of OIDs here: https://ep.advantech-bb.cz/application-notes#snmp-oids
And MIB files are located here: https://bitbucket.org/bbsmartworx/snmp-mib/src/master/
Example with signal strength:
Imagine the router having a perfectly stable connection, but the 4G signal strength fluctuates slightly all the time. Meaning it can be jumping 1-2dB all the time. This would generate SNMP Trap every time the value changes. Which in the real world scenario is not a desirable outcome. We are interested in big jumps in signal strength.
For this scenario the possibility to configure variation in signal strength is essential for filtering out unnecessary SNMP Traps, which would normally be sent.
Nothing is perfect
Few rabbit holes to consider. Sending on exception is great, but.
We do expose the setting of the time interval in which the values are read and compared against the historical values. Basically other brands or solutions, who do not expose the time interval have a time interval as well, but the end user does not have the option to change it.
Why is this a “problem”?
The value can slowly creep up or down and the system will not send SNMP Trap as the slow creep is not a big jump.
Here is an example:
2020-03-22 06:45:19 snmpTrapSenderd[8375]: Signal quality BIG jump = -11
2020-03-22 06:46:19 snmpTrapSenderd[8375]: ...once in 60 sec - 1358
2020-03-22 06:47:19 snmpTrapSenderd[8375]: ...once in 60 sec - 1359
2020-03-22 06:47:19 snmpTrapSenderd[8375]: Signal strength BIG jump = -112
2020-03-22 06:47:19 snmpTrapSenderd[8375]: Signal quality BIG jump = -15
2020-03-22 06:48:19 snmpTrapSenderd[8375]: ...once in 60 sec - 1360
2020-03-22 06:49:20 snmpTrapSenderd[8375]: ...once in 60 sec - 1361
2020-03-22 06:50:20 snmpTrapSenderd[8375]: ...once in 60 sec - 1362
2020-03-22 06:51:20 snmpTrapSenderd[8375]: ...once in 60 sec - 1363
2020-03-22 06:52:21 snmpTrapSenderd[8375]: ...once in 60 sec - 1364
2020-03-22 06:53:21 snmpTrapSenderd[8375]: ...once in 60 sec - 1365
2020-03-22 06:54:21 snmpTrapSenderd[8375]: ...once in 60 sec - 1366
2020-03-22 06:55:22 snmpTrapSenderd[8375]: ...once in 60 sec - 1367
2020-03-22 06:56:22 snmpTrapSenderd[8375]: ...once in 60 sec - 13682020-03-22 06:56:22 snmpTrapSenderd[8375]: Signal quality BIG jump = -14
As we can see the BIG jump is for values of -15 and -14 few minutes apart. What this indicates is the slow creep in between those readings.
Some conclusion
All tools need to be used with some consideration. At the moment we have included these values in SNMP Trap on exception User Module for Advantech routers:
- Signal Strength (variation)
- Signal Quality (variation)
- Mobile Technology
- Mobile Cell
- Internal Temperature
I am open to add more values, if it makes sense. At the moment none of the User Modules are publicly available. If you want to test drive or use it. Let me know.
If you have any questions or suggestions. Please let me know
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