An overlay network uses flexible neighbor selection based on network address translation (NAT) to define routing between nodes. The NAT type is used as a flexible neighbor selection criteria, either alone or in conjunction with other criteria. A method of selecting a neighboring node for a first node in a distributed hash table network includes determining a desired key value for a node finger table entry and requesting a set of candidate neighboring nodes near this desired key value. The method determines a network address translation type of each of the set of candidate neighboring nodes and ranks the set of candidate neighboring nodes accordingly. The method selects one of the set of candidate neighboring nodes based on the ranking. The NAT types of candidate neighboring nodes are determined by sending probe messages or from data received from a central overlay network server.