Updated July 22, 2016
This article provides brief information and steps to resolve the issue when subnets do not scan in manual or automatic modes, and the user is unable to edit or modify SNMP credentials.
The issue is similar to IPAM scans not running, however the SNMP credentials under IPAM settings cannot be added, modified or changed.
The IPAMBusinessLayer.log in the server shows the following:
2016-07-19 15:04:51,032  ERROR SolarWinds.IPAM.ScanningEngine.ScanStateManager (null) - Unable to update database with subnet scanner state. Will wait 20 seconds then retry.
System.FormatException: Invalid length for a Base-64 char array or string.
at System.Convert.FromBase64_Decode(Char* startInputPtr, Int32 inputLength, Byte* startDestPtr, Int32 destLength)
at System.Convert.FromBase64CharPtr(Char* inputPtr, Int32 inputLength)
at System.Convert.FromBase64String(String s)
at SolarWinds.Orion.Security.CryptoHelper.DecryptShort(String encryptedText)
at SolarWinds.Orion.Security.CryptoHelper.Decrypt(String encryptedText)
at SolarWinds.IPAM.BusinessObjects.SNMPCred.FromDataReader(IDataReader reader)
at SolarWinds.IPAM.Storage.DAL.SNMPCredDAL.Get(String SqlPostfix)
at SolarWinds.IPAM.ScanningEngine.ScanInitializer.CreateSubnetScan(Int32 subnetId, PingSweepDhcpJobSettings& jobsettings, TimeSpan& timeout)
at SolarWinds.IPAM.ScanningEngine.ScanStateManager.CreateSubnetScanJobSettings(IJobSchedulerHelper scheduler, ScanInstance instance, JobDescription& jobDescription, ScanState& state)
at SolarWinds.IPAM.ScanningEngine.ScanStateManager.StartJobs(List`1 changeList, List`1 removeList)
IPAM version 3 or later
The issue is caused by a problem within the SNMP credentials for IPAM stored in the database. Either the credentials are corrupted or the settings for the credentials are invalid.
Example: A SNMP v1 credential has the AuthMethod and PrivMethod entries you will find for an SNMP v3 configuration
When the scan attempts to start, it will go to the database to gather all the SNMP credentials for use during the scan. If that information does not match what it expects or the data is corrupted, the process cannot continue and job faults, causing it to try again and repeat until it is successful.
Note: You must have access to the database, whether from the Orion Database Manager or from the SQL Management Studio.
Verify if the scans are now running.
You should now be able to re-insert your SNMP credentials through IPAM Settings > Manage SNMP Credentials.