Problem: ISPs need to provide specific interface metrics to individual customers. Since Zabbix RBAC is strictly Host Group-based, each customer requires a dedicated host. However, polling the same edge router independently from hundreds of customer hosts multiplies SNMP traffic and overloads the router's control plane.

Current Limitations:

• Calculated items do not support macro expansion for remote host keys (e.g., last(/EdgeRouter/net.if.in[\{$IF_INDEX}]) fails). This blocks the ability to pass the argument from value obtained during host prototype creation.

• Dependent items strictly require the master item to reside on the same host.

• Current viable workarounds require external middleware and zabbix_sender.

Proposed Solution: Allow Dependent Items to select a Master Item located on a different host.

Use Case Execution (ISP Scenario):

1. A single "Edge Router" host polls all interface data once via SNMP (Master Item).

1. "Customer" hosts are created and assigned to isolated Host Groups for RBAC.

1. Items on "Customer" hosts are set as Dependent Items, linking directly to the Edge Router's Master Item to extract their specific interface metrics via preprocessing.

Business Value: Enables native Zabbix RBAC for multi-tenant environments with a single polling cycle and zero external scripting.