When Applications Manager performs automatic discovery, why are newly discovered servers categorized as 'Unknown'?

When Applications Manager performs automatic discovery, why are newly discovered servers categorized as 'Unknown'?

Applications Manager automatically discovers the running servers within the range given by the user and adds them as a node.

Reason:

SNMP agent is not running in the host. We add the monitor under 'Unknown' category.

Solution: 

If the system has SNMP agent running in it Application Manager will be able to discover the correct OS. If not, go to Monitor details page under Unknown category, click on Edit Monitor and configure the details.