Let's build a small VoIP topology with Cisco phones.

This is the router and switch side of the VoIP build. It uses the router as the call manager, TFTP and DHCP server. We configure everything from the ground up:
interfaces
DHCP pools
telephony service
ephones
and even monitor session to watch the traffic.

If you want more VoIP you can get a copy of the Packet Guide to Voice over IP from O'Reilly: https://www.oreilly.com/library/view/packet-guide-to/9781449339661/

Or watch my VoIP playlist: https://www.youtube.com/watch?v=oOEXUUi9-Vw&list=PLrancVv1TdY_wgFqNb6CJDHBCaOhyo56_