Contention-based forwarding (CBF) has proven to achieve a good performance in routing in mobile and vehicular ad hoc networks. CBF's main advantage is that it does not require the knowledge about the local neighborhood, eliminating, therefore, the periodic beacon exchange that causes degradation in the network performance, especially when the density of the neighborhood is high. On the other hand, the main issue that the contention-based forwarding faces is packet duplications, which mainly occurs due to the hidden node problem. This paper introduces a suppression algorithm for contention-based forwarding to eliminate packet duplications, called Sender-based Suppression and referred to as SS-CBF. In addition to the idea of dividing the radio range of the sending node into Reuleaux triangle zones, SS-CBF assigns a time delay to every zone, which aggregates to the timer value, set by the nodes, to form the time required for deferring. Moreover, the Sending node is involved in the suppression process in order to prevent unwanted nodes from transmission. SS-CBF is simulated using OPNET 14.5 modeler and evaluated against area-based suppression scheme in terms of network overhead and effective throughput.