The Internet is facing severe routing scalability problem. The Internet Service Providers cannot afford to upgrade their routers at the pace of routing table growth. Therefore, FIB aggregation has been proposed. However, current single-nexthop FIB aggregation solutions cannot provide a satisfactory performance. In this paper, we first propose the next hop of strict partial order (SPO next hop) to construct the Nexthop-Selectable FIB (NSFIB). The approach guarantees that NSFIB-based aggregation performs better than single-nexthop FIB aggregation, especially in larger and denser backbone networks. We then provide the NSFIB-based aggregation algorithms. According to our simulation, our algorithms can shrink the FIB to 5% and the aggregation performance does not degrade when the network density increases, both of which are a great improvement overhead single-nexthop FIB aggregation.