Wireless Mesh Networks (WMNs) may be broadly classified into two categories: Layer 2 and Layer 3 WMNs. This article focuses on the Layer 3 WMN, which provides the same service interfaces and functionalities to the conventional mobile host (MH) as the conventional wireless local area network. Three essential design issues to realize seamless mobility management in the Layer 3 WMN are identified and systematically discussed in this article. They are IP address resolution, location management, and Media Access Control (MAC) address resolution. The Layer 3 WMN backbone requires systematic management of the IP and MAC addresses of each MH, which can be realized by four basic approaches: centralized management, home management, replication management, and distributed management. It is shown that the address pair management architecture is fundamental to realizing efficient packet forwarding and address resolution. Design guidelines are provided to realize Layer 3 WMN supporting seamless MH roaming, considering the applicability of address pair management architectures with regard to WMN scale and client mobility; this applicability is considered based on a qualitative evaluation of the management overhead and handover performance.