Distribution of outside IP addresses across the MS-ISAs is dependent on the ingress hashing algorithm. Because traffic from the same subscriber is always pre-hashed to the same MS-ISA, the corresponding outside IP address also must reside on the same ISA. CPM runs the hashing algorithm in advance to determine on which MS-ISA the traffic from particular inside subnet lands and then the corresponding outside IP address (according to deterministic NAT mapping algorithm) is configured in that particular MS-ISA.