Hello raj You can setup QoS setting in router to give voice packet expedite forwarding. please read following  Cisco  guide  http://www.cisco.com/c/en/us/td/docs/ios/12_2/qos/configuration/guide/fqos_c/qcfmcli2.html http://www.cisco.com/c/en/us/td/do...

To Raj, Did you configure QoS for the Voice. When QoS setup with EF class voice traffic get first priority.