The following steps explain Preview campaign, or agent redial flow:
POM instructs MPP to launch a Nailup call to Agent.
MPP2 sends INVITE to the Agent on Avaya Aura® Communication Manager (CM) / Avaya Aura® Call Center Elite (CCElite) via System Manager (SM). On completion of INVITE transaction, the Agent call gets anchored on MPP.
In Preview campaign or Agent Redial, POM asks MPP to launch another call to the customer with Agent Nailup call in conference.
MPP sends INVITE to the Customer, which lands on Gateway via SM. Gateway tries to connect to the Customer outside enterprise.
On successfully connecting to the Customer, Gateway completes the INVITE transaction, and the Customer call gets anchored on MPP, where it is already conferenced to the Agent Nailup call.