For a list of available options and usage notes, run "./snmpWalk --help". These undocumented options are also available: "-sl1" for noAuthNoPriv, and "-sl2" for authNoPriv.
The timeout value increases in snmpwalk after each try. If an snmpwalk works correctly with a timeout of 10s, it does not necessarily mean that 10s will be enough for Discovery.
snmpwalk uses snmp getnext. Use snmpbulkwalk instead to use getBulk.
Even if the snmpwalk result looks correct, there might be some missing oids caused by timeouts. This can be verified with the number of lines returned by snmpwalk and the number of lines found in the MVC file of a device capture.
A timeout can be caused by an incorrect credential (wrong or unsupported version/key/community/securityname/method or security level)
An error "Unsupported securitylevel" can be caused by a permission issue in the scanned snmp agent.
An SnmpWalk failure is enough to confirm that some prerequisites of Discovery are not met: the snmp port must be reacheable, the network must allow the snmp traffic (at least), the snmp credential must be correct and the agent must be reasonably responsive.