The following is excerpted from the IP Discovery Guide
Access Mode determines what protocols are used to both discover and monitor the system and its components. Valid values for autodiscovery are ICMPSNMP and ICMPONLY. The default is ICMPSNMP, meaning that both ICMP and SNMP protocols are used to discover and manage the system. When ICMPONLY is selected, discovery does not send SNMP polls to the system and cannot, therefore, discover the system and its components. Instead, the system is added to the topology as a Host and is monitored only for connectivity.
Please refer to the IP Discovery Guide for more information.