Discovery identifiers

After Discovery classifies a CI, it uses identifiers to determine if the device already exists in the CMDB.

Discovery launches special identity probes that accumulate identification data for each device and feed that data into the identifiers, which determine the action that Discovery must take for each device. Identifiers accurately determine the identity of the device to prevent the creation of duplicate CIs. This identification step only takes place for the Configuration item type of discovery, not for the other types of discovery.

The identity probe in the base Discovery system can be configured to ask the device for information such as its serial numbers, name, and network identification. The results of this scan are processed by an identity sensor, which then passes the results to the identifier. The identifier then attempts to find a matching device in the CMDB. If the identifier finds a matching CI, the identifier either updates that CI or does nothing. If the identifier cannot find a matching CI, it either creates a new CI or does nothing. If Discovery is configured to continue, the identifier launches the exploration probes configured in the classification record to gather additional information about the device. Exploration probes can be multiprobes or simple probes.

This diagram shows the processing flow for classifying and probing devices with identifiers configured.

Discovery identifiers

CMDB identifier tables

Table Description
Identifier [cmdb_identifier] Stores all identifier rules.
Identifier Entry [cmdb_identifier_entry] Stores all the identifier attributes.

Identifier rules

The default Discovery system contains these identifier rules, each of which is associated with a specific CI type (the sys_class_name field on the CI record) or the table in the Applies to field and contains the appropriate attributes for discovering CIs from the specified table. Where necessary to discover all possible occurrences of an attribute, tables from related lists (Search on tables) are included in the rule. For more information, see Create or edit a CI identification rule.

Table 1. CMDB identifier rules
Rule Applies to table/attributes Search on table/attributes
ESX Server Rule ESX Server [cmdb_ci_esx_server]
  • correlation_id
none
Hardware Rule Hardware [cmdb_ci_hardware]
  • serial_number
  • serial_number_type
  • name
  • ip_address
  • mac_address
  • Serial Number [cmdb_serial_number]
    • serial_number
    • serial_number_type
  • Network Adapter [cmdb_ci_network_adapter]
    • ip_address
    • mac_address
Storage Server Rule Storage Server [cmdb_ci_storage_server]
  • cim_object_path
  • name
  • serial_number
  • serial_number_type
  • mac_address
  • ip_address
  • Serial Number [cmdb_serial_number]
    • serial_number
    • serial_number_type
  • Network Adapter [cmdb_ci_network_adapter]
    • ip_address
    • mac_address
WBEM Service Rule WBEM Service [cmdb_ci_wbem_service]
  • cim_object_path
none

Matching strategy for the hardware rule

The sys_class_name cannot be an attribute for independent rules, such as cmdb_ci_hardware. If your Discovery identification strategy depends on matching a CI with a specific class, you must create a new rule for each class you want to use for matching and specify that class in the Applies to field of the Identifier form.

For example, you can create an identifier for a Linux server with different attributes than the Hardware Rule. You might only want to use the machine name, IP address, and MAC address for identification. Your new rule would look like this:
Figure 1. Linux identifier rule
Linux identifier rule

Evaluation order for Discovery identifiers

Custom identifiers must have different Order values than those of the default identifiers. Discovery

parses identifiers and attributes in sequence from low order numbers to high. You can create identifiers to run before or after the default identifiers, or mixed in with the identifiers from the base system. To prevent any identifier or rule from running, disable it by clearing the Active check box. The evaluation order for CMDB identifiers is established within each rule and only controls the parsing order of the attributes in that rule.
Figure 2. Evaluation order in CMDB identifier rules

Properties for processesing duplicate CIs

You can control how Discovery handles duplicates using properties installed with Identification and Reconciliation. Use the glide.identification_engine.skip_duplicates and glide.identification_engine.skip_duplicates.threshold properties.

Properties that control identifier versions

All instances use identifiers from the CMDB Identification and Reconciliation framework. Upgrades from pre-Geneva versions still preserve the legacy identifiers, but you can switch to the new identifiers using a property: glide.discovery.use_cmdb_identifiers. If you upgraded from a pre-Geneva version, you must manually add this property and set it to true to use the new identifiers. If you upgraded from Geneva or later releases, this property is available in the System Properties [sys_properties] table. To preserve functionality in custom legacy identifiers, convert them to the new CMDB identifier rules format before enabling this property. The system does not reconfigure your custom identifiers to the new framework automatically.
Note: When Service Mapping is active, the new identifiers from the CMDB Identification and Reconciliation framework are always used regardless of the property value.