Communication systems and methods are presented for aggregating sites when connectivity to a core and zone controller therein is lost. A local controller provides multicast control to sub-sites within a locally aggregated network after detecting loss of connectivity to the core. The local controller assigns different multicast addresses than multicast addresses assigned by the zone controller. A sparse and dense mode protocol is used for multicast traffic outside and within the locally aggregated network, respectively. Conventional resources, but not trunked resources, are assigned addresses and groups. An isolated site is able to connect to the network in the event of core failure so that conventional multicast traffic traverses a direct link between each isolated site and the network, thereby extending the locally aggregated network. Multicast addresses available to be assigned by a local controller within any locally aggregated networks can be the same as those assigned by other local controllers.