For a Master Bridge with extensions 1xxx and a Slave Bridge with extensions 2xxx, is using a prefix in Outbound Rules required?

Using a prefix in Outbound Rules is optional in the scenario described because the extension numbering schemes for the Master Bridge (1xxx) and the Slave Bridge (2xxx) do not conflict. Since the extensions are clearly defined and separated between the two bridges, the 3CX system is able to route calls appropriately without the need for a prefix to distinguish between the two.

The main purpose of a prefix in Outbound Rules is to help delineate between different sets of extensions or to specify how calls are routed based on dial patterns. In this case, since the master and slave extensions are in different ranges, the system inherently understands which bridge to route the calls to without any additional instructions. Thus, using a prefix becomes optional and not a necessary requirement for the proper functioning of the outbound call routing in this particular setup.

In other situations where extensions might overlap or if more complex routing requirements exist, a prefix could be essential to ensure calls are directed properly. However, in this scenario, the distinct numbering alleviates that need.