Multihoming and multipath forwarding have been promising approaches to improve both the scalability and availability of the Internet. However, they incur overhead by increasing the routing table size due to multiple entries for the same network or the packet header size due to inclusion of multiple locators. To avoid this problem, new mechanisms has been proposed recently to assign topologically aggregatable locators to hierarchical networks, to encode multiple locators into a compact form code, and to perform efficient packet forwarding based on the encoded compact locator. These mechanisms support both automatic locator assignment and multiple locator-based intelligent forwarding. To take full advantages of handling multiple locators in hosts, ID/locator split-based host architecture that isolates the transport layer from the network layer is a suitable choice. In this paper, we present the design and implementation of an ID/locator split-based host architecture that supports the new network-layer forwarding mechanism well, in addition to the mobility and multihoming features.