IP Address Consolidation and Reconfiguration in Enterprise Networks

Private IP addressing is commonly used in enterprise networks. Different enterprises or even different locations/business units of the same enterprise may use the same IP address ranges as long while those networks are separate. Consequently, during mergers and acquisitions, or network consolidations within an enterprise, overlapped and conflicted IP segments (subnets) arise frequently. These must be identified and resolved to allow communication between any pair of source and destination hosts in the merged networks. Furthermore, the combined network may unnecessarily use many disparate IP address ranges which increases the size of the routing tables and makes routing integrity verification difficult. In this paper, we identify different conflict scenarios and consider ways of resolving those conflicts to minimize manual changes and to minimize the routing table sizes. The problem turns out to be NP-hard and rather complex, and we devise effective heuristics to solve the problem. By taking some real-world examples, we show that by changing 6-8% of the subnet addresses the outlined method can effectively resolve the subnet conflicts. The scheme also reduces the number of subnet entries by 80-90% by consolidating the subnet entries, which significantly reduces the routing table sizes.