About MLPP Domain Setup
In Cisco Unified Communications Manager Administration, use the menu path to configure MLPP domains.
An MLPP domain specifies the collection of devices and resources that are associated with an MLPP subscriber. When an MLPP subscriber that belongs to a particular domain places a precedence call to another MLPP subscriber that belongs to the same domain, MLPP service can preempt the existing call that the called MLPP subscriber is on for a higher precedence call. MLPP service availability does not go across different domains.
MLPP Domain Configuration Tips
You can add secure MLPP over SIP trunks by configuring a Resource Priority Namespace Network Domain and Resource Priority Namespace List.