An engineer is configuring a new directory number in the Call Manager. Which field is responsible for incoming calls restrictions?

A Route Partition is a logical container that groups directory numbers and route patterns to control reachability, but it does not apply dynamic policy-based restrictions to calls arriving at a specific DN.

Private Line Automatic Ringdown (PLAR) automatically dials a pre-configured destination when the line goes off-hook and has no function in filtering or restricting incoming calls.

Calling Search Space (CSS) determines which partitions a device or line can access when placing outgoing calls and governs outbound call routing, not restrictions on incoming calls to a directory number.

When an External Call Control Profile is assigned to a directory number, CUCM sends a routing query to an external route server application for each incoming call before connecting it - the external application evaluates policy rules and can accept, reject, or redirect the call, making this profile the mechanism that enforces incoming call restrictions at the DN level.