I need to do a device discovery which is working fine for version 1,2 because the community name by default "public" help me on this, but for the version 3 the credentials are required, do ou know any tool o method to know that ?
As described in https://www.rfc-editor.org/rfc/rfc3414#section-4 you can send an empty v3 pdu. If the device supports v3 protocol it will respond (a report message) with it's snmpEngineID.
'This may be accomplished by generating a Request message with a securityLevel of noAuthNoPriv, a msgUserName of zero-length, a msgAuthoritativeEngineID value of zero length, and the varBindList left empty.'