In order to offer a better network survivability, it is crucial that a network manager can realize restorable traffic assignment in response to traffic dynamics and facility network reconfiguration. In this paper, I presented an optimal virtual path routing control for survivable ATM networks to minimize the expected amount of lost flow upon restoration from a network failure. The amount of lost flow is calculated based on the fast restoration algorithm such that it gives an optimal traffic distribution with the minimum service interruption. The fast restoration and optimal flow assignment have two contradicting requirements. In order to accommodate these contradicting requirements, the VP manager uses two-step restoration approach. This paper focuses on the problem of the long-term reconfiguration, which is also used for the network-wide restoration. It has been found through numerical experiments that convergence to a nearoptimum is possible by properly choosing parameters.