The Hybrid Model
This type of configuration incorporates the best of both worlds.There is automatic
overflow to the PSTN for calls destined for the WAN which are unable to
allocate sufficient resources. It only needs one anonymous device for each Cisco
CallManager (cluster), thus minimizing the overhead of having to mesh the Cisco
CallManagers. It does require two routes for each destination, however, one to
the WAN and one to the PSTN.The drawback is you need to configure the dial
plan on the gatekeeper and the Cisco CallManager.