This paper studies the effect of rerouting for augmenting aggregate based resource allocation in the trade-off between overhead and utilization. Aggregation is a common approach to address the scalability issue in resource allocation. However, resources committed in bulk may be under utilized while other resource requests are being turned down for lack of resources in some shared links. The aim of rerouting is to free up committed resources for better utilization by reusing resources vacated by terminated flows and by moving existing flows to alternative paths.Our results show that rerouting improves performance over a wide range of network loads on two different network topologies. In particular, we show that depending on the network load and topology, it is possible to reduce both blocking rate and routing cost.