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There are two basic types of 802.11 networks: 1) networks that operate as single "independent" basic service sets (IBSSs) and 2) networks that operate as extended service sets (ESSs), also known as infrastructure networks. Infrastructure networks have access points (APs) that may be interconnected to other APs within an ESS via a distribution system (DS) to extend the range and scalability of an infrastructure network. Also, they may have stations (STAs) that associate with a neighboring AP in order to access the DS service. On the other hand, an IBSS consists only of STAs and does not support the DS service. Protocols that enable multihop routing in IBSS networks have been proposed in the lETF's MANET working group. This paper describes an 802.11 access point that can combine with other such APs and with standard STAs to form a mobile, 802.11 ESS that is an infrastructure network, but incorporates the mobility features typical of a multihop ad hoc network. The new architecture is called a dynamic backbone subnet based on 802.11, or simply, DBS/802.11. Externally, a DBS/802.11 subnet provides network services very much like an Ethernet, which simplifies its connection to other IP networks. Both a simulation model and a Linux implementation of DBS/802.11 have been developed. We show some results from a field test scenario designed to verify the operation of the DBS/802.11 implementation using mobile nodes in a dynamic, interference prone environment.