A common error is that an SNMP request times out before it completes. There are a number of reasons why this error might occur:
The system might be busy and therefore drops SNMP packets.
The network might be busy and therefore drops or delays SNMP packets.
A large bridge forwarding table might be causing the SNMP agent not to respond in time. Discovery uses the bridge forwarding table to determine connectivity.
If the error occurs because the system or network is busy, you should rediscover the system when the system or network is less busy.
If you notice an excessive number of timeouts during the discovery process, you should consider increasing the timeout values for discovery polling.