The Gatekeeper Model
This dial plan model helps clean up the overhead inherent within the Cisco
CallManager model.This is because the Cisco CallManager only needs to maintain
one intercluster trunk known as the anonymous device.This device is like a
point-to-multipoint connection in frame relay, as the Cisco CallManagers don’t
need to be fully meshed. In this set up, the gatekeeper is able to use the anonymous
device to route calls through the network to the correct Cisco
CallManager (or cluster).
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You can set this model up for exclusionary clusters.What this means is that
there is no automatic overflow for calls destined for the WAN which are unable
to complete due to insufficient resources. In this configuration, you need two
route patterns, one to the WAN and one to the PSTN.When users are unable to
connect over the WAN, they need to dial the PSTN number to access the other
site.The dial plans are configured and executed within the gatekeeper, so when
you add new Cisco CallManagers, or change the dial plan, you only need to configure
the gatekeeper.