Abstract: Hash routing is an effective approach for coordinating a collection of web proxies. In this paper, we present a comprehensive analytical model for hash routing which takes into consideration a number of factors: original request distribution, object allocation strategy, speeds of the proxies and cache hit ratios. Based on this model, the optimal hash routing problems for static and dynamic client configurations are investigated. Two schemes, OBJ-OPT and OBJ/DNS-OPT, are proposed to reduce the response times of web requests. OBJ-OPT optimizes object allocation under static client configuration, and OBJ/DNS-OPT optimizes both object and DNS allocations under dynamic client configuration. Extensive trace-driven simulations have been conducted to evaluate the proposed schemes. The results show that they significantly outperform the intuitive scheme based only on the speeds of the proxies.