This article highlights design principles for building ENUM DNS servers on a hybrid IPv4/IPv6 internetworking environment and provides examples for illustrating the main ideas. Basically, any ENUM DNS servers, as different from ordinary DNS servers, should meet the TELECOM carrier level (e.g., high reliability, capacity and speech quality, etc.). Current Internet is mainly based on IPv4, which has shown its inability on adapting itself to many real-world problems. The IPv6 protocol stack, with new characteristics such as 128-bit address space, intrinsic security and QoS supports, has shown to be superior to IPv4 for implementing these applications. However, most people still have limited IPv6 operating experience. The dual-stack IPv4/IPv6 model is usually adopted by most sites as a solution for migrating to native IPv6 environment. In this article, a knowledge-based system, called iDNS-MS, is developed to help insure the smooth operation of their ENUM DNS systems.