Wireless mesh networks (WMNs) comprise of mobile and static nodes which communicate wirelessly. WMNs have several unique features such as self-organizing, self-configuring and self-healing and are being used in many applications such as metropolitan area networks and disaster and rescue operations etc. Routing in WMNs is challenging as the network topology and connectivity in WMN are very dynamic due to unpredictable node mobility, interference, distributed wireless channel access and limited battery power of mobile devices in WMNs. This paper describes the challenges and the state of the art in provisioning of Routing over WMNs.