1- Configuration of the telephony service : The table below shows the necessary instructions to be executed at the router's CLI. Note : The switch needs to be configured first as per the instructions in the figure above.

Instructions
telephony-service
max-ephones (tag1)
max-dn (tag2)
ip source-address (ip address where option 150 resides) port 2000
ephone-dn 1
number (extension number 1)
ephone-dn 2
number (extension number 2)
exit (we exit config-telephony back to config mode)
ephone 1
mac-address (mac address of telephone 1)
type 7960 (Cisco's IP phone model)
button 1:1