IP Telephony System is very important today because of its functions make organization’s effectiveness and effiency increase. With IP Telephony system, a company can control the usage of each telephone in their company, and integrated it with their computer network so the maintenance is become efficient. IP Telephony system built in one of P.T. Multipolar’s client is used the IP Telephony system solution from Cisco. Components used to implement this solution are Cisco CallManager which is installed in Media Convergence Server to process calls and set up fitures in the IP Telephony system, IP Phones, router and switch. All the components except the IP phones should be configured properly to make the systems fit to the user needs. As a result, all the communication systems (IP Telephony system and computer network) in the company are unified, easier process of troubleshooting and maintenance, various fitur to support the user’s activities, and limited outside calls for every staff in the company.