Troubleshooting SNMPv3 monitoring issues

SNMPv3 protocol is the latest and most secure version. Encryption and authentication may take their toll on the v3 traffic so in many cases admins decide to stay on v2. Yet sometimes you need to go for it. Learn what to check if you encounter issues with SNMPv3 monitoring.

Check the credentials

Yes, the most obvious, yet still most prone to errors thing to check are the credentials.

1. Start with checking if the SNMP monitoring profile set in the NetCrunch is for the correct SNMP version.
2. Then check if:
   • username,
   • authentication type,
   • encryption type,
   • passwords
   • and finally, the context name is correct.

Remember!

• If the correct profile wasn't provided during Atlas creation, the SNMP monitor will be not enabled for discovered SNMP devices, so you have to enable monitor and provide the correct SNMP profile.

• Also, if you add the SNMP device manually to the Atlas, you have to set the correct profile in Node Settings as well.

Adjust connection timeout

Credentials are correct but you still got timeouts on the SNMP monitor and NetCrunch shows no data? Perhaps the monitored device is a little bit slower and needs a bit more time to respond.

Navigate to Node SettingsMonitoringSNMP

Here you can change the timeout value from default 5000 ms to a maximum of 60.000 ms (6 seconds), according to your needs.

Limit number of concurrent requests

It happens sometimes, that adjusting SNMP connection timeout is not enough, because there are just too many concurrent requests. A common symptom for such issues is when the Cisco device throws alert:

input queue full errors

In such a case, you can limit the number of concurrent requests.

Again, navigate to Node SettingsMonitoringSNMP

Now, mark the checkbox 'Limit concurrent requests' and provide the desired number.

Check with a different program

Yup, double-checking with something else than NetCrunch can at least give you a hint if there is a problem in NetCrunch itself, or if there is something wrong with the device. You can use e.g. SNMP View program (available in NetCrunch from the context menu when RMB-click on the problematic device).

Reboot SNMP device

The good ol' 'Have you tried to turn it off/turn it on?' mantra. If everything else fails, and you are still unable to gather data from the device, check on the device itself. Sometimes only the reboot can make it work again. Caution advised!

snmptroubleshooting