There has been an extensive study in constructing the routing tables during the past few years. Although the existing works have certain advantages, those approaches either use complicated data structures which result in large storage requirement and high complexity for updating/building the forwarding table or they are not scalable to fit in Internet protocol version 6 (IPv6). In this work, we propose a fast forwarding-table construction algorithm. With the modified multiway search tree, we can further reduce the depth of the tree and eliminate the storage for pointers. It leads to reduce the FT size and shorten the routing-table lookup time. While considering the route flaps, the forwarding performance will degrade by only 3.1% with 4000 BGP updates per 30 s in the worst case. Moreover, it is simple enough to fulfill the need of the fast packet forwarding. An extension approach to solve the IPv6 routing lookup is also presented for the future deployment.