With the growth of Internet, it becomes a challenging problem to test the running characteristics of routing protocol implementations in realistic large-scale networks. An Internet routing emulation system (IRES) is developed as a test bed to test and analyze the above characteristics. A novel approach by combining Internet topology generation and routing protocol implementation is proposed, and the architecture of IRES is presented. Then the Internet hierarchical topology is analyzed and a method is proposed to transform GT-ITM model to BGP-OSPF oriented Internet topology. In the given examples, by measuring the routing interaction with CISCO2600 router, its computation complexity of the OSPF protocol implementation in the CISCO2600 router is O((lgN)⁴), and the upper bound it supports is given. The experimental results show that as a test bed, IRES has an important role that cannot be replaced by others.