A credential test may succeed.
 

A device capture may fail and the last thing written in the UI is:

OR

 

 

This problem can occur on many different devices, and has been observed on:
 

1.3.6.1.4.1.9.1.1201 Cisco ASA 5585-SSP-60-SC Router, Firewall
F5 Load Balancers

 

... and some Lexmark printers like: 

Root cause 1: 
By default, Discovery asks for a large chunks of data at one time from the device, using the "Use GETBULK" option. Some devices may be unable to transfer so much data at one time without hitting a timeout.

Solution 1: 
Disable "Use GETBULK", as follows:

Edit the SNMP credential used by the device, and uncheck the "Use GETBULK" option.  By default, the "Use GETBULK" option is checked.


                         
Discovery versions prior to 11.0 do not show a "Use GETBULK" checkbox in the SNMP credential. 
On those older versions, do this instead: Root cause 2: 
(not confirmed) the scan may fail because of the Cisco defect below:

CSCti16586 :  ASA 8.2(1)11 failed to return MIB data for SNMPV3 GetBulk request.

See http://www.cisco.com/en/US/docs/security/asa/asa84/release/notes/asarn84.html#wp581504

To confirm the root cause: try this solution:

Solution 2:
Upgrade to latest/defect fixed Cisco OS and rescan.

Workaround 2:
See solution 1 to Disable "Use GETBULK"

 

Root cause 3: 
Lexmark problem with SNMP getbulks

To confirm the root cause, disable GetBulk as described in Solution 1.

Solution 3: 
Contact the vendor for a solution.

Workaround 3:
Disable GetBulk as described in Solution 1.

NOTES: