Internal Calls
The creation of dial plans for internal calls to IP phones registered within a Cisco
CallManager cluster is very simple.When the phone is initially configured, it is
assigned a directory number (DN).This DN is maintained throughout the configured
life of the phone. For example, if the phone is used in an office where
your users move frequently within the LAN, their phones can be unplugged and
connected to a different network jack, yet maintain their connection properties
(DN).When the phone is reconnected, it will update the Cisco CallManager
with its new IP address.