Hello,
Yes, you can enable IP connectivity between the small offices to the main site in that region to reach HQ site. Once this is done, you must think in some general ideas to choose the best deployment model.
For example, if WAN connectivity is stable, you can run a Multisite Centralized deployment. Branch IP phones will register to the CUCM cluster in the HQ site. You must run SRST/CME-as-SRST in your branch offices and add some local lines for PSTN access. This model will reduce administration and maintenance.
In the other hand, if your WAN connectivity is unstable and prone to flapping states, then you can run a Multisite Distributed deployment. You will run CME in your branch offices for local registration of IP phones and add local lines as a primary option for PSTN access or as a backup option. The distributed model will introduce more administration and maintenance.
Remember that, in either deployment model, you should implement an end-to-end QoS strategy.
You can read more from here:
http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/8x/models.html
Hope it helps, please rate if it does.
Regards,
- Adrian.
