In an embodiment, a method comprises: detecting a change in a multiple-switch configuration in a data communications network comprising a plurality of packet data switches configured as roots of multicast trees. In response to detecting that the multiple-switch configuration has changed, a first value, a second value and a third value representing limits on a number of multicast trees supported in the network and prioritization of the switches are retrieved. The method further comprises determining a type of the multiple-switch configuration change. In response to determining that the type indicates that a first switch was added to the multiple-switch configuration, using at least the first, second and third values, it is determined whether to configure the first switch as a first root in the multiple-switch configuration. The method is performed by one or more computing devices.