By default, the snmpcollector gets information from devices using an snmp bulk request, including up to a maximum of 20 OIDs, (the default number). Unfortunately, some snmp devices will not accept an snmp GetBulk of this size and snmpcollector can see errors like this:
Starting to discover device MAP-MIA-KCE-CE03 for metric family MetricFamily [metricFamilyName=NormalizedSystemInfo] with Vendor Cert systemMib
snmp error D4293c5258d1d266a93a55ecb346ebd93/Non-pollable scalars
Unable to collect OID on device SnmpDevice D4293c5258d1d266a93a55ecb346ebd93: null
com.nimsoft.snmppoller.poller.common.CollectorException: SNMP Error : 1
To resolve this, open the snmpcollector raw configuration, navigate to the setup folder and add the key, "MAX_BATCH". Set the value to a number less than 20. 3 was shown to work well on some Cisco 3850s, but trial and error may need to be used for other devices.
It is also possible to add or alter settings for SNMPRETRIES (default 2), and SNMPTIMEOUT (default 2000 milliseconds).
Note that the MAX_BATCH setup key setting applies to all devices that are discovered, including the devices that can handle larger snmp bulk request. The discovery process will take longer but this solution should allow all devices to be discovered successfully.