IPv6 is an Internet protocol which was engineered to replace Internet protocol previously and currently used, which is IPv4. IPv6 has 128-bit addressing space, therefore it can accommodate huge number of hosts more than IPv4. IPv6 provides enhanced features like autoconfiguration, efficient and flexible header, integrated security and mobility. IPv4 supports 4.249.967.296 (4,294 x 109 x 2564) address, which is not sufficient compared to exponential host growth of Internet today. In the other hand, IPv6 supports around 3,4 x 1038 (340 undecillion) address, or nearly 4,3 x 1020 (430 quintillion) address per inch square on earth (Wikipedia). IETF has recommended IPv6 as Internet protocol to replace IPv4, but apparently until now, there is no significant implementation, especially in Indonesia to get IPv6 fully used and migrated to. This final project objective will be giving a feasibility analysis on IPv6 implementation as future Internet communication protocol regarding IPv4 depletion. Case study was conducted at PT. Excelcomindo Pratama (XL) and PT. Indo Internet (Indonet), as organization representation which have implemented IPv6. Feasibility analysis was assessed and seen from 6 factors; infrastructure readiness, operating system support, application availability, regulation, performance, and cost. Performance and cost factors are two most-contributed concerns in implementing IPv6. Keywords: Computer Network, Internet Protocol, Feasibility Analysis, IPv4, IPv6 ix+91 pages; 24 figures; 14 tables; 4 attachments; Bibliography: 32 (1981-2008)